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PREFACE
A FEw lines will suffice to explain why we have compiled - the present volume, to what wants it responds, and what its sphere of usefulness may possibly embrace.
In our teaching of plastic anatomy, especially at the Ecole des Beaux-Arts—where, for the past nine years, we have had the very great honour of supplementing the teaching of our distinguished master, Mathias Duval, after having been prosector for his course of lectures since 1881—it is
- our practice to give, as a complement to the study of human
anatomy, a certain number of lessons on the anatomy of those animals which artists might be called on to represent. Now, we were given to understand that the subject
treated in our lectures interested our hearers, so much so
that we were not surprised to learn that a certain number repeatedly expressed a desire to see these lectures united in book form.
To us this idea was not new; for many years the work in question had been in course of preparation, and we had collected materials for it, with the object of filling up a void of which the existence was to be regretted. But our many engagements prevented us from executing our pro- ject as early as we would have wished. It is this work which we publish to-day.
Putting aside for a moment the wish expressed by our hearers, we feel ourselves in duty bound to inquire whether the utility of this publication is self-evident. Let it be clearly understood that we wish to express here our opinion
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PREFACE vil
on this subject, while putting aside every personal senti- ment of an author.
No one now disputes the value of anatomical studies made in view of carrying out the artistic representation of man. Nevertheless—for we must provide against all con- tingencies—the conviction on this subject may be more or less absolute ; and yet it must possess this character in an intense degree in order that these studies may be profit- able, and permit the attainment of the goal which is proposed in undertaking them. It is in this way that we
| _ ever strive to train the students whose studies we direct;
not only to admit the value of these studies, but to be materially and deeply convinced of the fact without any restriction. Such is the sentiment which we endeavour to create and vigorously encourage. And we may be per- mitted to add that we have often been successful in this direction.
Therefore it is that, at the beginning of our lectures, and in anticipation of possible objections, we are accustomed
_ to take up the question of the utility of plastic anatomy.
And in so doing, it is in order to combat at the outset the idea—as mischievous as it is false—which is sometimes imprudently enunciated, that the possession of scientific knowledge is likely to tarnish the purity and freshness of the impressions received by the artist, and to place shackles on the emotional sincerity of their representation.
It is chiefly by employment of examples that we ap- proach the subject. These strike the imagination of the student more forcibly, and the presentation of models of a certain choice, although rough in execution, is, in our opinion, preferable to considerations of an order possibly more exalted, but of a character less clearly practical. Let us, then, ask the question : Those artists whose eminence nobody would dare to question, did they study anatomy ? If the answer be in the affirmative, we surely cannot permit ourselves to believe that we can dispense with a similar
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PREFACE ix
course. And, as proof of the studies of this class which
the masters have made, we may cite Raphael, Michel- angelo, and, above all, Leonardo da Vinci; and, of the moderns, Géricault. And we may more clearly define these proofs by an examination of the reproductions of their anatomical works, chosen from certain of their special writings.*
Accordingly, there is no scope for serious discussion, and it only remains for us to enunciate the opinion that it is necessary that we should imitate those masters, and, with a sense of respectful discipline, follow their example.
Here, with regard to the anatomy of animals, we pursue the same method, and the example chosen shall be that of Barye. His talent is too far above all criticism to allow that this example should be refused. The admiration which the works of this great artist elicit is too wide-spread for us to remain uninfluenced by the lessons furnished by his studies. It is sufficient to see the sketches relating to these studies, and his admirable casts from nature which form part of the anatomical museum of the Ecole des Beaux-Arts, to be convinced that the artistic tem- perament, of which Barye was one of the most brilliant examples, has nothing to lose by its association with re- searches the precision of which might seem likely to check its complete expansion.
In those sketches we find proofs of observation so scrupu- lous that we cannot restrain our admiration for the man
* Mathias Duval and A. Bical, ‘L’anatomie des Maitres.’ Thirty plates reproduced from the originals of Leonardo da Vinci, Michelangelo, Raphael, Géricault, etc., with letterpress and a history of plastic anatomy, Paris, 1890.
The manuscripts of Leonardo da Vinci of the Royal Library, Windsor, ‘Anatomy, Foliz A.,’ published by Théodore Sabachnikoff, with a French translation, written and annotated by Giovanni Piumati, with an introduction by Mathias Duval. Edouard Rouveyre, publisher, Paris, 1898.
Mathias Duval and Edouard Cuyer, ‘ History of Plastic Anatomy: The Masters, their Books, and Anatomical Figures’ (Library of Instruction of the School of Fine Arts), Paris, 1898.
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PREFACE xi
w ose ardent imagination was voluntarily subjected to the toil of study so profound. |
_ If the example of Barye, with whom we associate the names of other great modern painters of animals, can deter- _ mine the conviction which we seek to produce, we shall be sincerely glad. To contribute to the propagation of useful ideas, and to see them accepted, gives a feeling of satisfac- tion far too legitimate for us to hesitate to say what we should feel if our hope be realized in this instance.
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CONTENTS
INTRODUCTION _ GENERALITIES OF COMPARATIVE ANATOMY - - -
| CHAPTER I fe STEOLOGY AND ARTHROLOGY :
| THE TRUNK : - - - -! F. THE POSTERIOR LIMBS - - - ms
THE POSTERIOR LIMBS IN SOME ANIMALS e é THE SKULL OF BIRDS - : 7 : :
CHAPTER II
_ MYOLOGY :
THE MUSCLES OF THE TRUNK S : : MUSCLES OF THE ANTERIOR LIMBS~ - ; ; MUSCLES OF THE POSTERIOR LIMBS~ - ; 2 MUSCLES OF THE HEAD : : é :
CHAPTER III
EPIDERMIC PRODUCTS OF THE EXTREMITIES OF THE FORE AND HIND LIMBS - - .
4 CHAPTER IV PROPORTIONS °
PROPORTIONS OF THE HEAD OF THE HORSE =- -
: CHAPTER V THE PACES OF THE HORSE : :
xill
PAGE
78 go
I3I 162 . 200 232
247
273
282
LIST OF ILLUSTRATIONS
PAGE A HUMAN SKELETON IN THE ATTITUDE OF A QUADRUPED, To GIVE A GENERAL IDEA OF THE POSITION OF THE BONES IN OTHER VERTEBRATES - ~~ - ‘ . sa SIZE OF THE ATLAS COMPARED WITH THE TRANSVERSE DIMENSIONS OF THE CORRESPONDING PARTS OF THE SKULL IN MAN - - - - - - 7 SIZE OF THE ATLAS COMPARED WITH THE TRANSVERSE DIMENSIONS OF THE CORRESPONDING REGIONS OF THE SKULL IN A DoG - - - - - 8 LUMBAR VERTEBRZ OF A QUADRUPED (THE HORSE): SUPERIOR SURFACE - - - - - 9 A TRANSVERSE SECTION OF THE THORAX OF A MAN PLACED VERTICALLY—THAT IS TO SAY, IN THE DIRECTION WHICH IT WOULD ASSUME IN A MAN PLACED IN THE ATTITUDE
OF A QUADRUPED (A DIAGRAMMATIC FIGURE) - + 83 A VERTICAL SECTION OF THE THORAX OF A QUADRUPED (DIAGRAMMATIC) - - - - - - 14
STERNUM OF A BIRD (THE Cock): Lert SIDE, EXTERNAL SURFACE - - - - - - POND iy 3 ANTERIOR LIMB OF THE Bat: LeEFrr SIDE, ANTERIOR SURFACE - - - - - - m0) ANTERIOR LIMB OF THE SEAL: LEFT SIDE, EXTERNAL SURFACE - - - - - . a Bee SITUATION AND DIRECTION OF THE SCAPULA IN THE
- HumMaAN BEING, THE TRUNK BEING HORIZONTAL, AS IN QUADRUPEDS. VERTICAL AND TRANSVERSE SECTION
OF THE THORAX (DIAGRAMMATIC FIGURE) - <; 22 POSITION AND DIRECTION OF THE SCAPULA IN QUADRU- PEDS. VERTICAL AND TRANSVERSE SECTION OF THE THORAX (DIAGRAMMATIC FIGURE) - - - LEFT SCAPULA OF THE HUMAN BEING, POSTERIOR SURFACE, PLACED IN THE POSITION WHICH IT WOULD OccUPY IN THE SKELETON OF A QUADRUPED - - a3 Lert ScAPULA OF A Horse: EXTERNAL SURFACE Ce XV
to i)
XV1 LIST OF ILLUSTRATIONS
PAGE
14. VERTICAL AND TRANSVERSE SECTION, AT THE SITE OF THE SHOULDERS, OF THE THORAX OF THE HORSE (Dia- GRAMMATIC FIGURE) - - - - - 24
15. VERTICAL AND TRANSVERSE SECTION, AT THE PLANE OF THE SHOULDERS, OF THE THORAX OF THE Doc (D1a- GRAMMATIC FIGURE) - - - - - (3A
16. LEFT CLAVICLE OF THE CAT: SUPERIOR SURFACE (NATURAL © SIZE) - - - - - - - 26
17. CLAVICLE OF THE DoG (NATURAL SIZE) - . - - 26
18. SKELETON OF THE SHOULDER OF A BIRD (VULTURE): ANTERO-EXTERNAL VIEW OF THE LEFT SIDE - ee
19. INFERIOR EXTREMITY OF THE LEFT HUMERUS OF A FELIDZ (Lion) - - - - - - 7 “ae SHOWING THE PRESENCE OF A SUPRATROCHLEAR PROCESS 31
21. SKELETON OF A BIRD (VULTURE) : LEFT SURFACE - » See
22. THE HUMAN HAND RESTING FOR ITS WHOLE EXTENT
20. INFERIOR EXTREMITY OF THE LEFT HUMAN HUMERUS, | j ON ITS PALMAR SURFACE: LEFT SIDE, EXTERNAL |
SURFACE - - - - . : > ae 23. THE HuMAN HAND RESTING ON ITS PHALANGES: LEFT SIDE, EXTERNAL SURFACE > - 3G 24. THE HUMAN HAND RESTING ON THE TIPS OF SOME OF | ITS THIRD PHALANGES: LEFT SIDE, EXTERNAL VIEW - 36 | 25. SUPERIOR EXTREMITY OF THE BONES OF THE HUMAN . FOREARM: LEFT SIDE, SUPERIOR SURFACE - « \ 50a 26. SUPERIOR EXTREMITY OF THE BONES OF THE FOREARM oF A Doc: LErtT LimB, SUPERIOR SURFACE - - 39 27. SUPERIOR EXTREMITY OF THE BONES OF THE FOREARM OF THE HorsE: LEFT LIMB, SUPERIOR SURFACE - 40
28. INFERIOR EXTREMITY OF THE BONES OF THE FOREARM OF A MAN: LEFT SIDE, POSTERIOR SURFACE, POSITION OF SUPINATION - - - . - - i 29. INFERIOR EXTREMITY OF THE BONES OF THE FOREARM OF A Doc: LEFT SIDE, ANTERIOR SURFACE, NORMAL
POSITION—THAT IS, THE POSITION OF PRONATION - AI 30. INFERIOR EXTREMITY OF THE BONE OF THE FOREARM
OF THE HorRSE: LEFT SIDE, ANTERIOR SURFACE « “ez 31. SKELETON OF THE SUPERIOR LIMB OF A BIRD (VULTURE) :
LEFT SIDE, EXTERNAL SURFACE - - - 47
32. SUPERIOR LIMB OF THE HUMAN BEING, THE DIFFERENT SEGMENTS BEING PLACED IN THE ATTITUDE WHICH THE CORRESPONDING PARTS OCCUPY IN BIRDS: LEFT SIDE,
EXTERNAL SURFACE - - - - - 48 33. SKELETON OF THE BEAR: LEFT LATERAL SURFACE - 50 34. SKELETON OF THE Doc: LEerr LATERAL SURFACE - 52 35. SCAPULA OF THE Doc: LEFT SIDE, EXTERNAL SURFACE 53 36. Lerr SCAPULA OF THE CAT: EXTERNAL SURFACE - 53
37. SKELETON OF THE FINGER OF A FELIDE (LION): LEFT SIDE, INTERNAL SURFACE - - * same
FIG. 38. 39 40. 4l.
54.
LIST OF ILLUSTRATIONS
SKELETON OF THE PIG: LEFT LATERAL SURFACE - SKELETON OF THE Ox: LEFT LATERAL SURFACE - SKELETON OF THE HorSE: LEFT LATERAL SURFACE~ - FLEXION OF THE HUMERUS: RIGHT ANTERIOR LIMB OF THE Horse, EXTERNAL SURFACE (AFTER A CHROMO- PHOTOGRAPHIC STUDY BY PROFESSOR MAREY) - - EXTENSION OF THE HUMERUS: RIGHT ANTERIOR LIMB OF THE HorsE, EXTERNAL SURFACE (AFTER A CHROMO- PHOTOGRAPHIC STUDY BY PROFESSOR MAREY) - - THE Lert IL1Aac BONE OF THE HUMAN BEING: Ex- TERNAL SURFACE, PLACED IN THE POSITION WHICH IT WOULD OCCUPY IN THE SKELETON OF A QUADRUPED~ - Lert IL1Ac BONE OF A QUADRUPED (HORSE) : EXTERNAL SURFACE - - - - - - - PuBic REGION OF THE PELVIS OF A MARSUPIAL (PHA- LANGER, Fox) - . - - - - PELVIS OF A BIRD (THE COCK): EXTERNAL SURFACE, LEFT SIDE - - - - - - POSTERIOR LIMB OF THE HORSE PLACED IN THE POSITION WHICH IT SHOULD OCCUPY IF THE ANIMAL WERE A PLANTIGRADE: LEFT LimB, EXTERNAL SURFACE - SKELETON OF THE Foot OF A BIRD (THE Cock): LEFT SIDE, EXTERNAL SURFACE - - - - PELVIS OF THE DOG, SEEN FROM ABOVE - - - PELVIS OF A FELIDE (LION), VIEWED FROM ABOVE - PELVIS OF THE Ox: SUPERIOR SURFACE - - TARSUS OF THE Ox: POSTERIOR LEFT LIMB, ANTERO- EXTERNAL SURFACE - - - - - PELVIS OF THE HORSE: SUPERIOR SURFACE - - TARSUS OF THE HorSE: LEFT POSTERIOR LIMB, AN- TERIOR SURFACE | - - - - - EXTENSION OF THE LEG: RIGHT POSTERIOR LIMB OF THE HorsE, EXTERNAL SURFACE (AFTER A CHRONOGRAPHIC STUDY BY PROFESSOR MAREY) - - - HuMAN SKULL: MEASURE OF THE FAcIAL ANGLE BY THE METHOD OF CAMPER. ANGLE BAC= 80° - - SKULL OF THE HorRSE: MEASURE OF THE FACIAL ANGLE BY THE METHOD OF CAMPER. ANGLE BAC=13° - SKULL OF ONE OF THE FELID (JAGUAR): LEFT LATERAL ASPECT - ae ee - - - - SKULL OF THE LION: LEFT LATERAL ASPECT - - SKULL OF THE Doc: LEFr LATERAL ASPECT - - SKULL OF THE Pic: LEFT LATERAL ASPECT - - SKULL OF THE Ox: LEFT LATERAL ASPECT - - SKULL OF THE HorsE: LEFT LATERAL ASPECT - SKULL OF THE HARE: LEFT LATERAL ASPECT - - SKULL OF THE Cock: LEFT LATERAL SURFACE - -
TRUNK - ~ - - - - -
74
74
79
IOI
104
107 110
IIo
113 113 115 117 119 [21 123 128
MyYoLocy oF THE HorRSE: ANTERIOR ASPECT OF THE.
132
‘oil LIST OF ILLUSTRATIONS
FIG.
67.
68. 69. 70. 71.
72
73
74
75
76.
77
78. 79 80. 8I.
82
83
84.
85 86.
87. 88. 89.
90. QI. 92. 93- 94
MYOLOGY OF THE HORSE: INFERIOR ASPECT OF THE TRUNK - - ~ - - - - MYOLoGY OF THE DoG: SUPERFICIAL LAYER OF MUSCLES MYOLOGY OF THE Ox: SUPERFICIAL LAYER OF MUSCLES MYOLOGY OF THE HORSE: SUPERFICIAL LAYER OF MUSCLES MYOLOGY OF THE HORSE: PANNICULUS MUSCLE OF THE TRUNK - - - - - - - MYOLOGY OF THE HORSE—SHOULDER AND ARM: LEFT SIDE, EXTERNAL SURFACE - - - - MyYOLoGy OF THE Doc: Lert ANTERIOR Lims, EXTERNAL ASPECT - - - - - ~ - MYOLOSY OF THE Ox: LEFT ANTERIOR LimB, EXTERNAL ASPECT - - - - - - - MYoLoGy OF THE HorsE: LEFT ANTERIOR LIMB, Ex- TERNAL ASPECT - - - - - - MYoLoGy oF THE Doc: LeErrr ANTERIOR LIMB, _ IN- TERNAL ASPECT - - - - - ~ MYOLOGY OF THE HoRSE: ANTERIOR LIMB, LEFT SIDE, INTERNAL ASPECT - - - - - Lert ANTERIOR LIMB OF THE HORSE: INTERNAL ASPECT LEFT ANTERIOR LIMB OF THE HORSE: EXTERNAL ASPECT Lert ANTERIOR LIMB OF THE HORSE: EXTERNAL ASPECT DIAGRAM OF THE POSTERIOR PART OF A TRANSVERSE SECTION PASSING THROUGH THE MIDDLE OF THE, LEFT FORE-LIMB OF THE DoG: SURFACE OF THE INFERIOR SEGMENT OF THE SECTION - - - - DIAGRAM OF A HORIZONTAL SECTION OF THE MIDDLE OF THE FOREARM OF THE LEFT LEG OF THE HORSE: SURFACE OF THE INTERIOR SEGMENT OF THE SECTION - MYOLOGY OF THE HORSE: THE ANTERIOR TIBIAL MUSCLE (FLEXOR OF THE METATARSUS), LEFT LEG, ANTERIOR VIEW - - - - - - - MyYoLoGy oF THE Doc: Lert HIND-LIMB, EXTERNAL ASPECT - - - - - - - MYOLOGY OF THE Ox: LEFT LEG, EXTERNAL ASPECT - MYOLOGY OF THE HorsE: LEFt HIND-LIMB, EXTERNAL ASPECT - - - ee - - - MYOLOGY OF THE DoGc: Lerrt HIND-LIMB, INTERNAL ASPECT - - - - - - - MYOLOGY OF THE HorSE: LeEFt HIND-LEG, INTERNAL ASPECT - - - - . - ~ MYoLoGy OF THE Doc: MAsTICATORY MUSCLES (A DEEPER DISSECTION THAN THAT SHOWN IN FIG. 90) - MYOLOGY OF THE DoG: MUSCLES OF THE HEAD - MYOLOGY OF THE Ox: MUSCLES OF THE HEAD - MYOLOGY OF THE HoRSE: MUSCLES OF THE HEAD - CLAW OF THE DoG: INFERIOR SURFACE - - LEFT HAND OF THE DoG: INFERIOR SURFACE, PLANTAR TUBERCLES - . - - - -
PAGE
“135
141
143.
146 148 166 178 180 182 190 192 194
196 196
198
198
214
216 218
220 222 223 233 235 237
239 249
249
Byte
98.
ITro.
ITl.
IT2.
113.
114.
II5. 116.
117.
LIST OF ILLUSTRATIONS
VERTICAL ANTERO-POSTERIOR SECTION OF THE FOOT OF A HorRSsE ~ - . - - - THIRD PHALANX OF THE HORSE: LEFT ANTERIOR LIMB, EXTERNAL SURFACE - - ~ - - Lert ANTERIOR Foot OF THE HORSE : ANTERIOR ASPECT LEFT ANTERIOR FOOT OF THE HORSE: EXTERNAL ASPECT VERTICAL AND TRANSVERSE SECTION OF A LEFT HUMAN Foot: OUTLINE OF THE SURFACE OF THE POSTERIOR SEGMENT OF THIS SECTION (DIAGRAMMATIC FIGURE) - INFERIOR SURFACE OF A FORE-HOOF OF THE HORSE: LEFT SIDE - - - eee - - - THIRD PHALANX OF THE HorRSE: LEFT ANTERIOR LIMB, INFERIOR VIEW - - - - - THIRD PHALANX OF THE HORSE: LEFT POSTERIOR LIMB, INFERIOR VIEW - - eh dot! ag - INFERIOR SURFACE OF A HIND-HOOF OF A HoRSE: LEFT SIDE - - - - - - - LEFT POSTERIOR FooT oF A HORSE: EXTERNAL ASPECT Foot OF THE Ox: LEFT SIDE, ANTERO-EXTERNAL VIEW THE PROPORTIONS OF THE HORSE (AFTER BOURGELAT) - PROPORTIONS OF THE HORSE (AFTER COLONEL DUHOUS- SET} - - - - - - - PROPORTIONS OF THE HEAD OF THE HORSE, VIEWED IN PROFILE (AFTER COLONEL DUHOUSSET) - - THE SAME DESIGN AS THAT OF FIG. 108, ON WHICH WE HAVE INDICATED, BY SIMILAR LINES, THE PRINCIPAL CORRESPONDING MEASUREMENTS - - - PROPORTIONS OF THE HEAD OF THE HORSE, SEEN FROM THE FRONT (AFTER COLONEL DUHOUSSET) - - THE SAME FIGURE AS FIG. 110, ON WHICH WE HAVE MARKED, BY SIMILAR LINES, THE PRINCIPAL MEASURE- MENTS WHICH CORRESPOND THERETO - - - HORSE OF WHICH THE LENGTH CONTAINS MORE THAN Two AND A HALF TIMES THAT OF THE HEAD, AND OF WHICH THIS DIMENSION (A, B) EXCEEDS THE HEIGHT HORSE OF WHICH THE LENGTH CONTAINS MORE THAN Two AND A HatF TIMES THAT OF THE HEAD, AND OF WHICH THIS DIMENSION (A, B) EXCEEDS THE HEIGHT - - - - - - - HORSE OF WHICH THE LENGTH CONTAINS MORE THAN Two AND A HALF TIMES THAT OF THE HEAD, AND OF WHICH THIS DIMENSION (A, B) Is INFERIOR TO THE HEIGHT - - - - - - - EXPERIMENTAL SHOES, INTENDED TO RECORD THE PRESSURE OF THE FOOT ON THE GROUND - - RUNNER FURNISHED WITH THE EXPLORATORY AND REGISTERING APPARATUS OF THE VARIOUS PACES - TRACING OF THE RUNNING OF A MAN (AFTER PROFESSOR MAREY) - - - - - - -
x1x PAGE 250 251 253 254 255 256 257 257 258 259 260 265
270
274
275
276
277
279
280
281 284 285
286
XX
FIG. 118.
I19.
120. I2I.
122. 123.
124. 125.
126. 127. 128.
129. 130. 131. +32. 133. 134. 135.
136
137. 138. 139. 140. 141. 142. 143.
LIST OF ILLUSTRATIONS
NOTATION OF A TRACING OF THE RUNNING OF A MAN (AFTER PROFESSOR MAREY)~ - - NOTATION OF VARIOUS MODES OF PROGRESSION OF A MAN (AFTER PROFESSOR MAREY)~ - si - SWING OF THE RAISED ANTERIOR LIMB (AFTER G. COLIN) SWING OF THE ANTERIOR LIMB ON THE POINT OF PRES- SURE (AFTER G. COLIN) - - - - POSTERIOR LIMB, GIVING THE IMPULSE (AFTER G. COLIN) NOTATION OF THE AMBLING GAIT IN THE HORSE (AFTER
PROFESSOR MAREY) - - - - ~.
Tue AMBLE: RIGHT LATERAL PRESSURE : . NOTATION OF THE GAIT OF THE TROT IN A HORSE (AFTER
PROFESSOR MAREY) . - - - - THE Trot: RicgHt DIAGONAL PRESSURE - - THE TrRoT: TIME OF SUSPENSION - - - NOTATION OF THE PACE OF STEPPING IN THE HORSE
(AFTER PROFESSOR MAREY)~ - - - - THE STEP: RIGHT LATERAL PRESSURE - - - THE Step: RIGHT DIAGONAL PRESSURE - - THE GALLOP: FIRST PERIOD - - - - THE GALLOP: SECOND PERIOD - - - - THE GALLOP: THIRD PERIOD-~ - - - - THE GALLOP: TIME OF SUSPENSION - - - NOTATION OF THE GALLOP DIVIDED INTO THREE PERIODS
OF TIME (AFTER PROFESSOR MAREY) - - ~ NOTATION OF THE GALLOP OF FOUR PERIODS IN THE
HorRSE (AFTER PROFESSOR MAREY) = - - - LEAP OF THE HARE (AFTER G. COLIN) - - - THE LEAP - - - - - - THE LEAP - - - - - - THE LEAP - - - - - - THE LEAP - - - - - - THE LEAP. zs . r “ a THE LEAP - - - - - -
PAGE 287 287 289
290 291
292 293
294 295 295
296 297
297 298
298
299 299
300
300 301 302 302 393 303 305 395
a ay ee
THE ARTISTIC ANATOMY OF ANIMALS
INTRODUCTION GENERALITIES OF COMPARATIVE ANATOMY
OF the animals by which we are surrounded, there are some which, occupying a place in our lives by reason of their natural endowments, are frequently represented in the works of artists—either as accompanying man in his work or in his amusements, or as intended to occupy the whole interest of the composition.
The necessity of knowing, from an artistic point of view. the structure of the human body makes clear the importance
we attach, from the same point of view, to the study of the
anatomy of animals—that is, the study of comparative anatomy. The name employed to designate this branch of anatomy shows that the object of this science is the study of the relative position and form which each region presents in all organized beings, taking for comparison the correspond- ing regions in man. The head in animals compared with the human head; the trunk and limbs compared to the trunk and limbs of the human being—this is the analysis we undertake, and the plan of the subject we are about to ‘commence.
Our intention being, as we have just said, the comparison of the structure of animals with that of man, should we
describe the anatomy of the human being in the pages
I
2 THE ARTISTIC ANATOMY OF ANIMALS
which follow? We do not think so. Plastic human anatomy having been previously studied in special works,* we take it for granted that these have been studied before undertaking the subject of comparative anatomy. We will therefore not occupy time with the elementary facts relative to the skeleton and the superficial layer of muscles. We will not dilate on the division of the bones into long, short, large, single, paired, etc. All these preliminary elements we shall suppose to have been already studied.
This being granted, it is, nevertheless, necessary to take a rapid bird’s-eye view of organized beings, and to recall the terms used in their classification.
Animals are primarily classed in great divisions, based on the general characters which differentiate them most. These divisions, or branches, allow of their being so grouped that in each of them we find united the individuals whose general structure is uniform ; and under the neme of verte- brates are included man and the animals with which our studies will be occupied. The vertebrates, as the name
indicates, are recognised by the presence of an interior
skeleton formed by a central axis, the vertebral column, round which the other parts of the skeleton are arranged.
The vertebrate branch is divided into classes: fishes) amphibians or batrachians, reptiles, birds, and mammals.
The mammals—from the Latin mamma, a breast—are characterized by the presence of breasts designed for the alimentation of their young. Their bodies are covered with hair, hence the name fzliféves proposed by Blainville ; and, notwithstanding that in some individuals the hairs are few, the character is sufficient to distinguish them from all other vertebrates. :
We find united in this class animals which, at first, seem out of place, such as the whale and the bat ; and, from their
external appearance alone, the former would appear to
* Mathias-Duval, ‘ Précis of Anatomy for the Use of Artists’: Paris, 1881. ‘Artistic Anatomy of the Human Body,’ third edition, plates by Dr. Fau, text with figures by Edouard Cuyer: Paris, 1896. ‘ Artistic Anatomy of Man,’ by J.C. L. Sparkes, second edition, text with 50 plates: Bailliére, Tindall and Cox, London, 1900.
INTRODUCTION 3
: belong to the fishes, and the latter to birds.. Yet, on study- ing their structure, we find that, not only do these animals
merit a place in the class which they occupy, because they
possess the distinctive characters of mammals ; but, still
further, their internal structure is analogous to that of man
and of the other individuals of this class.
Notwithstanding this similarity of structure, the eal is not without some points of difference from its neighbours the horse and the dog ; therefore, in order to place each of these animals in a position suitable to it, mammals are
_ divided into secondary groups called orders. The first of
these orders includes, under the name frimates, man and apes. The latter contain animals which approach birds in certain characters of their organism, forming a link between
_ the latter and mammals.
| . 3
We find, in studying the regions of the body in some of the vertebrates, that, while they present differences from the corresponding regions of the human body, they also offer most striking analogies. We can, for example, recognise the upper limb of man in the anterior one of quadrupeds, in the wing of the bat, in the paddle of the seal, etc. It is, so to speak, those variations of a great plan which give such a charm to the study of comparative anatomy.
The division of classes into orders, which we have just
_ mentioned, being still too general, it was found necessary to _ establish subdivisions—more and more _ specialized—to _ which the names families, genera, species, and varieties were _ given.
eye Tied sy
CHAPTER I
OSTEQLOGY AND ARTHROLOGY
THE TRUNK The Vertebral Column
We commence the study of the skeleton with a description of the trunk.
The trunk being, in quadrupeds, horizontal in direction
(Fig. 1), the two regions of which it consists occupy, for this
reason, the following positions: the thorax occupies the
anterior part, the abdomen is placed behind it ; the vertebral column is horizontal, and is situated at the superior aspect of the trunk ; it projects beyond the latter: anteriorly, to
articulate with the skull; and, posteriorly, to form the
skeleton of the tail, or caudal appendix.
The number of the vertebrz is not the same in all mam- |
malia. Of the several regions of the vertebral column, the cervical shows the greatest uniformity in the number of the vertebree of which it consists, with but two exceptions (eight or nine in the three-toed sloth, and six in the manatee) ;
we always find seven cervical vertebra, whatever the length ~
of the neck of the animal. There are no more than seven vertebre in the long neck of the giraffe, but they are very long ones ; and not less than seven in the very short neck of the dolphin, in which they are reduced to mere plates of bone not thicker than sheets of cardboard. If the cervical region presents uniformity in the number of its bones, it is not so with the other regions of the column. 4
OSTEOLOGY AND ARTHROLOGY eta
The following table shows their classification in some animals :
VERTEBRZ.
Cervical. Dorsal. Lumbar. Bear ~A sbi 7 14 6 Dog 7 13 7 Cat ; ‘ 7 13 7 Rabbit es 7 12 7 Pig ; 7 14 6 or 7 Horse ; es 7 18 6 or 5 Ass aaa 7 18 5 Camel aka 7 12 7 Giraffe... 7 14 5 Ox in : 7 13 6 Sheep... ‘ “a 13 6 ;
sds INN
Ed.CuyeR
Fic. 1.—A HuMAN SKELETON IN THE ATTITUDE OF A QUADRUPED. To GIVE A GENERAL IDEA OF THE POSITION OF THE BONES IN OTHER VERTEBRATES.
It is worthy of notice that in birds the number of the cervical vertebre is not constant, as in mammals ; they are
‘6 THE ARTISTIC ANATOMY OF ANIMALS
‘more numerous than the dorsal. These latter are almost always joined to one another by a fusion of their spinous processes ; the two or three last vertebre are similarly united to the iliac bones, between which they are fixed. The dorsal vertebre thus form one piece, which gives solidity to the trunk, and provides a base of support to the wings, for the movements of flying. There are, so to speak, no lumbar vertebre, the bones of that region, which cannot be differentiated from the sacrum, having coalesced with the bones of the pelvis.
VERTEBRA. Servibal. Dorsal. Vulture... “ 15 7 Eagle Ma nes 13 9 Cock em ‘ite 14 7 Ostrich er nes 18 9 Swan sas ads 23 fe) Goose Be ee 18 9 Duck has hes 15 9
In reptiles, the relation between the number of the cervical vertebree and that of the dorsal is very variable; some serpents are devoid of cervical vertebre, having only dorsal ones—that is, vertebrz carrying well-developed ribs.
VERTEBR&. | Cervical. | Dorsal. Lumbar. Crocodile : ... 7 14 3 Caiman 4 12 5 Boa 3 248 fe) Python O 320 fe) Viper 2 145 fo)
Regarding the direction of the vertebral column in animals, in which the trunk is not vertical, it is evident that the spinous processes point upward, and that in comparing them with those of man they must be arranged so that the superior surface of the human vertebra will correspond to the anterior
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OSTEOLOGY AND ARTHROLOGY a
surface of that of the quadruped. Of the cervical vertebre, the atlas and axis call for special notice. Apropos of the atlas, we find that it, in the human being, is narrower than _ the corresponding parts of the skull, and is therefore hidden _ under the base of the cranium (Fig. 2); in quadrupeds its width is equal to that of the skull, and sometimes exceeds, because of the great development of its wing-shaped trans- verse processes, that of the neighbouring parts of the head
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\
Fic. 2.—SIZE oF THE ATLAS COMPARED WITH THE TRANSVERSE DIMEN- SIONS OF THE CORRESPONDING PARTS OF THE SKULL IN MAN.
1, Atlas ; 2, mastoid process ; 3, external occipital protuberance ; 4, inferior maxilla.
(Fig. 3). On this account those transverse processes often project under the skin of the lateral surfaces of the upper part of the neck.
The axis is furnished on its enterior surface with the odon- toid process, which articulates with the anterior (or inferior) arch of the atlas, according to the direction of the neck. The spinous process, flattened from without inwards, is more or less pointed ; it is elongated from before backwards, so as partly to overlap the atlas and the third cervical vertebra.
_ We find that this process overlaps less and less the neigh- bouring vertebree when we examine in succession the bear, the cat, the dog, che ox, and the horse. With regard to the other vertebre of this region, they diminish in width from
8. THE ARTISTIC ANATOMY OF ANIMALS
the second to the seventh ; and, in some animals, the anterior surface of the body presents a tubercle which articulates with a cavity hollowed in the posterior surface of that of the vertebra before it ; this feature dwindles away in the dorsal and lumbar regions. ;
The spinous process, slightly developed in the third cervical vertebra, gradually increases in size to the seventh, the spinous process of which, long and pointed, well deserves the name of the prominent which is bestowed on it ; but it should not be forgotten that the spinous process of the axis is equally developed.
Fic. 3.—SIZE OF THE ATLAS COMPARED WITH THE TRANSVERSE DIMEN- SIONS OF THE CORRESPONDING REGIONS OF THE SKULL IN A Doa.
1, Atlas, 2; zygomatic arch; 3, external occipital protuberance; 4, inferior maxilla.
On the inferior surface of the body of each of the vertebree is found a prominent crest, especially well marked at the posterior part; this crest is but slightly developed in the bear and in the cat tribe, and is not found in swine.
The transverse processes of the cervical vertebre, from their relation to the trachea, are known as the tracheal processes.
The most marked characteristic of the dorsal vertebre is furnished by the spinous processes. They are long and narrow. As a rule, the, spinous processes of the, foremost
OSTEOLOGY AND ARTHROLOGY 9
_ dorsal vertebree are the most developed and are directed
eT a -
obliquely upwards and backwards. As we approach the last vertebre of this region, the processes become shorter and tend to become vertical, and the last ones are even, in some cases, directed upwards and forwards ; this disposition is well marked in the dog and the cat. In the cetaceans, on the contrary, the length of the spinous processes increases from the first to the last.
In the horse the spinous processes of the first dorsal
1 |
43
Fic. 4.—LuMBAR VERTEBR# OF A QUADRUPED (THE HoRSE): SUPERIOR SURFACE.
I, Spinous process ; 2, anterior articular process and transverse process of the first lumbar vertebra of the left side ; 3, costiform process.
vertebrae produce the prominence at the anterior limit of the trunk, where the mane ends, which is known as the withers.
The lumbar vertebre are thicker than the preceding ; they are known by their short and latterly-flattened spinous processes, and still more readily by their transverse processes, which, as they are evidently atrophied ribs, it is more accurate to denominate costiform processes (Fig. 4). These are long, flattened from above downwards, and directed outwards and forwards.
_ The true transverse processes are represented by tubercles
10 THE ARTISTIC ANATOMY OF ANIMALS
situated on the superior borders of the articular processes of each of the vertebre of the lumbar region. Apropos of these different osseous processes, we are reminded that they are also present in the human skeleton.
In the horse the costiform processes of the fifth and sixth lumbar vertebre articulate, and are sometimes ankylosed, one with the other ; the terminal ones articulate with the base of the sacrum. Sometimes the processes of the fourth and fifth are thus related ; this is the case in the figure (4) given ; here the costiform processes of the fourth and fifth vertebre articulate, and the two terminal ones have coalesced.
In the ox, the same processes are more developed than in the horse; their summits elevating the skin, produce, especially in animals which have not much flesh, prominences which limit the flanks in the superior aspect. The costiform processes of the last lumbar vertebre are separate from each other ; those of the latter are not in contact with the sacrum.
The Sacrum.*—This bone, single and median, is formed by the mutual coalescence of several vertebra, which vary in number according to the species observed.
Vertebre Constituting the Sacrum.—Bears, 5; dogs, 3; cats, 3; rabbits, 4; swine, 4; horses, 5; camels, 4; oxen, 5; sheep, 4.
The sacrum is situated between the two iliac bones ; with which it articulates, and contributes to the formation of the pelvis. It is obliquely placed, from before backwards, and from below upwards; immediately behind the lumbar section of the vertebral column ; and is continued by the coccygeal vertebrze, which form the skeleton of the tail.
It is triangular in outline, and is generally more narrow in proportion than in the human being. All things considered, it is more large and massive, and of greater density, in species which sometimes assume the upright posture, rather than in
* In human anatomy, the sacrum and the coccyx are studied as part of the pelvis; we, therefore, in the study of the artistic anatomy of man, study these bones with the bones of the lower limbs. Here we do not follow this plan. .In animals the sacrum and the coccyx, as a matter of fact, clearly continue the superior border of the skeleton of the trunk; hence we study them with the vertebral column.
OSTEOLOGY AND ARTHROLOGY IL
those which cannot assume that attitude ; for example, the sacrum of the ape, of the bear, of the dog, and of the opossum are proportionately larger than those of the horse.*
Its superior surface presents a crest, formed by the fusion of the spinous processes of the vertebre which form it. In certain species these processes are attached only by their
bases, and are separated from each other superiorly. In
the pig they are wholly wanting.
The Coccygeal Vertebrz. — These yertatirs, few in number (and sometimes ankylosed) in the human being, form in the latter a small series, the coccyx ; which is in- clined forwards, that is to say, towards the interior of the pelvis. In quadrupeds, on the contrary, their number is large ; they are not ankylosed, and they form the skeleton of the caudal appendix.
The first coccygeal vertebree—that is, those which are next the sacrum—present characters which are common to those
of other regions: they have a body, a foramen, and pro-
cesses. As we trace them backwards, these characters be- come gradually effaced; and they become little more than small osseous cylinders simply expanded at their extremities.
Direction and Form of the Spinal Column
The curves of the vertebral column are, in quadrupeds, slightly different from those which characterize the human spine. First, instead of their being, as in the latter, curves in the antero-posterior aspect, because of the general attitude of the body, they are turned.in the supero-inferior direction.
The cervical region is not a single curve, as in the human - being. It presents two: one superior, with its convexity looking upwards ; the other inferior, the convexity of which is turned downwards. This arrangement reminds one of that of a console.
* This is particularly striking only in those portions of the sacrum that are not in relation with the other bones of the pelvis. We think that the general form of this bone depends on the mode of its connexions with the iliac bones and the extent of the articular surfaces by which it is in contact with the latter.
12 THE ARTISTIC ANATOMY OF ANIMALS
The dorsal and lumbar regions are placed in a single curved
line, more or less concave downwards ; so that in the lumbar ~
region there is no curve analogous to that which exists in man ; a form which, in the latter, is due to the biped atti- tude—that is to say, the vertical position of the trunk. Briefly, there is in quadrupeds one dorso-lumbar curve ; and not both a dorsal and a lumbar, with convexities in oPPaare directions.
At the extremity of the dorso-lumbar region is the sacrum and the caudal appendix, which describe a curve of which the concavity is directed downwards and forwards.
It is necessary to point out that it is not the curves of the three anterior portions of the spinal column which deter- mine the form of the superior border of the neck and shoulders, and of the same part of the trunk. For the first portion, there is a ligament which surmounts the cervical region, and substitutes its modelling influence for that of the vertebre. It is the superior cervical ligament, which arises from the spinous process of the first cervical vertebre, and is inserted into the external occipital protuberance on the upper part of the posterior surface of the skull. The summits of the spinous processes of the vertebre alone give form to the superior median border of the trunk. In this connection we here repeat that it is not the general curvature of the vertebral column which produces the withers, but the great length of the spinous process of the first vertebre of the dorsal region.
The Thorax
' The dorsal vertebreze form the posterior limit in man, and
superior in quadrupeds, of the region of the trunk known as the thorax. A single bone, the sternum, is situated at the aspect opposite ; the ribs bound the thorax on its sides.
In its general outlines the thorax in quadrupeds resembles that of man—that is to say, that, as in the latter, the anterior portion—superior in the human being—is narrower than the part opposite. But the progressive widening takes place in a more regular and continuous fashion, so that it presents
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OSTEOLOGY AND ARTHROLOGY 13
a more definitely conical outline. This purely conical form _ is nevertheless found in the human species, but only during _ infancy ; the inferior portion of the thoracic cage being then widely expanded, because of the development of the ab- dominal viscera, which at that period are relatively large. But the proportionate measurements of the thorax are different. Indeed, we may recall that in man the thorax is
flattened from before backwards, so that the distance
between the sternum and the vertebral column is shorter than the distance from the rib of one side to the correspond- ing one of the opposite side (Fig. 5). In animals, on the contrary, it is flattened laterally. Its vertical diameter— measured from the sternum to the vertebral column—is greater than the transverse measurement (Fig. 6).
Fic. 5.—A TRANSVERSE SECTION OF THE THORAX OF A MAN PLACED VERTICALLY—THAT IS TO SAY, IN THE DIRECTION WHICH IT WOULD ASSUME IN A MAN PLACED IN THE ATTITUDE OF A QUADRUPED (A DIAGRAMMATIC FIGURE).
1, Dorsal vertebra; 2, sternal region; 32, costal region of one side; 3’, costal region of the other side.
From this results a peculiar arrangement of the muscles © that we are able to bring directly into prominence, which presents points of interest from the point of view of the con- . traction of the subcutaneous layer. Indeed, in man the region occupied by the pectorals is very broad ; it is a wide surface turned directly forward. In quadrupeds, this region of the pectorals is narrowed. It is not spread out, as in the preceding instances; and the appearance it presents is explained by the fact that the thorax is compressed laterally. If we examine the thorax on one of its lateral surfaces, the muscles, on the contrary, are more extended. We see the contour of the vertebral column, and the median part of the abdomen ; and, especially in the horse, between the great
14 THE ARTISTIC ANATOMY OF ANIMALS
dorsal and the great oblique of the abdomen, we find a large space, in which the ribs, with the intercostals which join them,
are uncovered ; the muscles in question separate the one
from the other, under the influence, it would seem, of the great dimensions of the lateral wall of the thorax.
The Sternum.—tThe sternum is, in quadrupeds, directed obliquely downwards and backwards; its form varies in different species. In the carnivora, it consists of eight bones,
V7
Fic. 6.—A VERTICAL SECTION OF THE THORAX OF A QUADRUPED (DIAGRAMMATIC).
1, Fifth dorsal vertebra ; 2, sternal region ; 3, costal region of one side ; 3’, costal region of the opposite side.
irregularly cylindrical in form, being slightly flattened from within outwards, and thickened at their extremities. They remain separate, and this contributes elasticity and flexibility to the thorax. The first nine costal cartilages articulate directly with the sternum. The first of these cartilages articulates with a nodule situated a little above the middle of the first bone of the sternum. |
In the horse the sternum is flattened laterally in its anterior portion, and from above downwards in its posterior
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——— a Ure
OSTEOLOGY AND ARTHROLOGY 15
half. The six bones which form the sternum are connected by cartilage. The keel-shaped piece, situated in front of the sternum, is also cartilaginous. This process, but slightly marked posteriorly, becomes more and more prominent in _ front, and terminates at its anterior extremity by a prolonga- tion, slightly curved backwards, which projects for some | _ centimetres beyond the cavity in which the first costal _ cartilage is received. This process is known as the tracheal | process, or rostral cartilage. The posterior extremity of the sternum, flattened from above downwards, ends in a car- F tilaginous plate ; concave superiorly, and convex inferiorly : _ this is the abdominal prolongation, or xiphoid appendix. In the ox, the sternum is formed of two distinct bones, which are united by an articulation. One, the anterior, is short, and forms the first portion of the sternum; it is _ slightly flattened from side to side, and vertical in direction. The other, the posterior, is longer, and is formed by the fusion of several small bones ; it is placed horizontally, and is flattened from above downwards. At the level of articu- lation of these two portions, and because of their different ‘directions, the bone is bent. This bend occurs at the point of articulation of the second costal cartilage. On the _ superior border of the anterior segment the cartilage of the first rib is articulated. The xiphoid appendix, which is cartilaginous, is attached to the extremity of a long process of the last bone of the sternum. The shape of the anterior extremity of the sternum is influenced by the presence or absence of clavicles. We have seen that in some quadrupeds the clavicles are wanting. In the first case, this extremity is large, and approaches in shape _ to the corresponding part of the human sternum, which is so _ clearly designed to give a point of support to the anterior _ bone of the shoulder. In the second, on the contrary, this _ extremity is narrow. The sternum in birds is very different from that in mam- _ malia, which we have been studying. It varies greatly in _ extent and shape, under the influence of certain conditions. _ To understand the cause of these variations it is necessary _ to remember that in man (as, indeed, in other animals ; but
16 THE ARTISTIC ANATOMY OF ANIMALS
the example of man, for that which follows, will be more striking, on account of the mobility of his upper limbs) the sternum gives origin to the pectoral muscles, and that these muscles are inserted into other parts of the thoracic limbs, — designed by their contraction to draw the arms downwards, forwards, and inwards—that is, when these are in a state of abduction and in a horizontal direction, they draw them towards the anterior surface of the thorax and downwards. Now, this movement is similar to that made by birds during flight. It is necessary to add that, in the latter case, the more the displacement of the upper limbs has of force and extent, the more the pectoral muscles are developed.
For these reasons, birds, in which, during flight, the move- . ments of the thoracic limbs—the wings—are necessarily energetic, present a great development of the pectoral muscles ; having consequently, because an extent of surface — for the origin of the muscles commensurate with their de-— velopment is necessary, a very large and peculiarly shaped sternum (Figs. 18, 6; and 21, 6). Indeed, not only is the sternum large, but, further, in order to form a deeper surface, proportionately adapted to the muscles which arise from and cover it, its anterior surface presents, in the median line, a — prominent crest known as the keel. This prominence forms ~ two lateral fosse. We cite as examples, the sternum of the © eagle, the vulture, the falcon, and the hawk. .
All birds are not, however, equally adapted to flight, for ) in the domestic cock, which flies but a short distance, and — badly, the sternum is less developed (Fig. 7); it is also diminished by slots, which diminish its surface. These slots, — two on each side, are called from their position the internal © and external slots. They are bounded by narrow, elongated, ~ bony processes, an internal and an external ; the expanded ~ lower extremity of the latter overlaps the last inferior ribs — (seep.1g). The part of the external border which surmounts this external process is hollowed out into grooves, which ~ receive the inferior ribs, and terminates superiorly in an © osseous projection known as the costal prominence. :
In the ostrich, the cassowary, and the apteryx, which run, ~
|
OSTEOLOGY AND ARTHROLOGY 17
4
but do not fly, the sternum has the form of a plate of bone
The shape of the sternum, cnimeleted to the faculty of light (or of swimming ; apropos of which we may cite the
and perform their functions only), or the absence of this faculty, has furnished the division of birds into two groups. ~ Inone are included, under the name Carinates (carina, keel), __ those in which the sternum is provided with a keel ; in the
G. 7.— STERNUM OF A BIRD (THE Cock): LEFT SIDE, EXTERNAL SURFACE.
1, Keel; 2,internalslot ; 3,externalslot ; 4,internal process ; 5, external process ; 6, inferior ribs; 7. costal process; 8, surface for articulation " with the coracoid bone.
The keel is developed in flying mammals (bats).
a Ribs and Costal Cartilages.—There are on each side of the thorax as many ribs as there are dorsal vertebre. in animals, as in man, the ribs which articulate with the ternum by their cartilages are called true, or sternal ribs; those whose cartilages do not articulate with the sternum 2
18 THE ARTISTIC ANATOMY OF ANIMALS
are called false, or asternal. The longer ribs are those situated in the middle region of the thorax.
The ribs are directed obliquely downwards and backwards, _ and this obliquity is more marked in the posterior ones than ~ in the anterior. They are, however, less oblique than in the human being ; what proves this is that the first ribinman _ is oblique, while in quadrupeds it is vertical. :
The curvature of the ribs is less pronounced in quadrupeds than in the human being, but this is not equal in all animals. _ The ribs of the bear are more curved than those of the dog ; _ the latter has ribs more curved than those of the horse. :
Each rib, at its vertebral extremity, presents, from within outwards, a wedge-shaped head for articulation with two — dorsal vertebre, a neck, and a tuberosity. External to the — tubercle are found some rough impressions, for muscular } attachments, which correspond to the angle of the human ~ rib.
In the following table, we give the number and classifica- _ tion of the ribs of some animals :
NUMBER OF THE RIBS ON EACH SIDE OF THE THORAX.
Sternal. Asternal. Bear.) i. ... 14 dividedinto g and 5 Dog 13 ae ae De 4 Cat | 13 ee ee 4 Rabbit 12 : = a 5 Pig 14 ye eas Ae 7 Horse 18 i ss > oy 10 Camel 12 os S Ae 4 Ox 13 ” 99 8 ” 5 Sheep 13 ” 9 8 ” 5
The costal cartilages, by which the first ribs are united to | the sternum (sternal ribs), whilst the latter are united one to the other without being directly connected with the — sternum (asternal ribs), are, as a rule, in quadrupeds, directed Ni] obliquely downwards, forwards, and inwards ; each forms, © with the rib to which it belongs, an obtuse angle more or less © open anteriorly. Their length is proportionate to that of the ribs. The cartilages, which are continued’ from the © asternal ribs, unite and form the borders, directed obliquely downwards and forwards, of the fossa which is found at the —
~OSTEOLOGY AND ARTHROLOGY 19
inferior and posterior part of the thorax, and which forms the lateral limits of the epigastric region. In the dog and cat ‘the ribs are thick and almost cylindrical ; the costal car- | tilages are thicker at the margin of the sternum than at their | fostal extremity. In the ox, the ribs are flattened laterally _-and are very broad, the more so as we examine a portion further from the vertebral column. From the second to the i twelfth they are quadrangular in the superior fourth, and H thicker than in the rest of their extent. The first costal cartilage is vertical ; the following ones are progressively
more oblique in a direction downwards and forwards. The ' our or five cartilages which succeed the first unite with slight hs obliquity. to the sternum ; their union with that bone gives | the impression of a very strong, well-knit apparatus. The _ costal cartilages which unite with the sternum are flattened laterally in the portions next the ribs, and flattened from ' front to back in the rest of their extent. In the horse the ribs increase in length from the first to the ninth ; they are flattened from without inwards, and increase width from the first to the sixth or seventh, and the fol- | lowing ones become narrower. The costal cartilages, from _ the second to the eighth, are, as in the ox, at first flattened 1 aerally, near the ribs; while near the sternum they are flattened from front to back. Lt In birds, the ribs are each furnished with a flat process | (Fig. 18, 10), which springs from the posterior border, is directed backwards, and overlaps the external surface of the succeeding rib. These processes are e not found, as a rule, on the first or last ribs - _ As for the costal cartilages, they are, as a rule, ossified, and receive the name of inferior ribs (Fig. 18, rr), united to \ ee preceding (superior ribs ; Fig. 18, 9) by articulation ; y the other extremity they are joined to the sternum ; the - rst superior ribs generally want them. Sometimes the last |: aferior rib becomes connected with the one that precedes it, not articulating with the sternum; and thus recalls the Telations of the asternal ribs which we have noticed 1 in our study of the mammals. : In the bat, as in birds, the costal saaiilaves are Secihied:
: ae
20 THE ARTISTIC ANATOMY OF ANIMALS
THE ANTERIOR LIMBS*
The anterior limbs, homologous to the upper limbs in man, are formed, as in the latter, of four segments: the shoulder, the arm, the forearm, and the hand. These limbs, considered in the vertebral series, present themselves under very different aspects, which are determined by the functions they are called upon to perform.
They constitute the forepaw in terrestrial mammals ; in aerial vertebrates they form wings; in aqueous mammals they act as paddles. In whatever series we study them,
eae"
Fic. 8.—ANTERIOK LIMB OF THE BAT: LEFT SIDE, ANTERIOR SURFACE.
1, Clavicle ; 2, scapula; 3, humerus; 4, radius; 5, cubitus; 6, carpus ; i 7, thumb ; 8, metacarpus ; 9, phalanges.
we can readily find the relationship of the different parts ; it is very easy to recognise the same bones in the upper limbs | of the human being, the wings of the bat (Fig. 8) and of birds (Fig. 21), and in the anterior paddles of the seal (Fig. 9) and of the dolphin. : In quadrupeds, the shoulder and arm are hidden, the © latter more or less completely, in the muscular mass which | binds it to the lateral wall of the trunk ; so that the anterior limbs only present ; free from the trunk: the elbow, forearm, and hand. | The Shoulder
In some vertebrates, the shoulder is formed of two bones the scapula and clavicle ; in others of only one bone—the scapula; the clavicle in this case does not exist.
* Consult Figs. 21, 33, 34, 38, 39, 46.
( OSTEOLOGY AND ARTHROLOGY 21
The Scapula or Omoplate.—The scapula is situated on the lateral surface of the thorax, and is directed obliquely, from above downwards and from behind forwards.
We must first recall, so as to be able to make a comparison, that in man this bone is placed at the posterior surface of the thoracic cage ; so that if we look at the human thorax
on one of its lateral aspects we see chiefly the external
border of the scapula; it is the external surface (homo- _logous to the posterior surface of the human scapula) which "we see in its full extent when we look on the same surface _of the thorax in quadrupeds.
_ Fic. 9.—ANTERIOR LIMB OF THE SEAL: LEFT SIDE, EXTERNAL SURFACE. 1, Scapula ; 2, humerus ; 3, radius; 4, ulna; 5, carpus; 6, metacarpus ; 7, phalanges of the fingers.
_ To sum up, if we fancy the human being in the position of the quadruped, the scapula will have its surfaces almost ‘parallel to the ground (Fig. 10) ; while in quadrupeds, the ‘surfaces are situated in a plane which is almost perpendicular to the ground (Fig. rr). This position of the scapula in an ‘almost vertical plane is designed to give the necessary point of support to the osseous columns that form the skeleton of the other portions of the anterior limbs.
Because of this position of the scapula (Figs. 12 and 13), the spinal border is superior, the cervical, anterior, and the axillary, posterior. In direct contrast to what obtains in the : human scapula, the spinal border is the shortest of the
|
22 THE ARTISTIC ANATOMY OF ANIMALS
three; except in the bat, and the majority of the
cetaceans.
In certain animals (in the ungulates [hoofed*|—pigs, oxen, sheep, horses) the superior, or spinal, border of the scapula is surmounted by a cartilage called the cartilage of prolongation.
This is the cause why the border to which it is fixed is so
Fic. 10.—SITUATION AND DIREc- TION OF THE SCAPULA IN THE HuMAN BEING, THE TRUNK BEING HORIZONTAL, AS IN QUADRUPEDS. VERTICAL AND TRANSVERSE SEC- TION OF THE THORAX (DIAGRAM- MATIC FIGURE).
1, Contour of the thorax; 2, 2, the scapula.
Fic. 11.—PoOSITION AND DIRECTION OF THE SCAPULA IN QUADRUPEDS. VERTICAL AND TRANSVERSE SEC- TION OF THE THORAX (DIAGRAM- MATIC FIGURE). x %
1, Contour of the thorax; 2, 2, the
scapula.
slightly noticeable under the skin in these animals ; indeed, in the upper part, the bone and cartilage are not distinguish- able in the contour of the corresponding region of the back ; _ being applied to the lateral surfaces of the spinous processes, _ the prominence formed by the extremities of which is directly continuous with the plane of the scapula (Fig. 16).
* For the definition of the word hoofed, see p. 37.
OSTEOLOGY AND ARTHROLOGY 23
_ In quadrupeds whose scapula, on the contrary, is wanting in the cartilage of prolongation (in the clawed,* such as the
eat and dog), the superior border of the scapula is visible, especially when the animal is resting on its fore-limbs, par- ticularly when it crouches ; at such a time the skin is mark- _ edly raised by that border; and the spinous processes of _ the vertebrz, beyond which it projects, occupy the bottom
iy 7 | . | | )
————
Fic. 12.—L&Ert SCAPULA OF THE HUMAN BEING, Pos-
Fic. 13.—LEFT SCAPULA OF A HORSE: EXTERNAL SURFACE.
spinal border ; _ border; 4,supraspinous fossa ;
TERIOR SURFACE, PLACED IN THE POSITION WHICH IT WOULD OccUPY IN THE SKELETON OF A QUAD-
RUPED. 1, Cervical border; 2,
3, axillary
1, Cervical border ; 2, spinal border— the scapula here represented, being from a hoofed animal, has a cartilage of exten- sion attached to its spinal border; 3, axillary border; 4, supraspinous fossa ; 5, subspinous fossa; 6, spine of the scapula; 7, glenoid cavity ; 8, coracoid process. The scapula of the horse has no
acromion process, but it is easy, if we compare the human scapula, to judge of the position which this process would occupy if it were present.
fossa; 6,
5, subspinous 7, glenoid
scapular spine ; / cavity; 8, coracoid process ; g, acromion process.
' of a fossa (Fig. 15). The internal surface of the scapula _ is turned towards the ribs; it is known, as in man (in whom ; _ this surface is anterior), as the subscapular fossa.
f Its external surface is divided into two parts by the spine _ ofthescapula ; which, in some animals, terminates inferiorly ina flat and clearly distinct process, the homologue of the
* For the definition of this word, see p. 37.
24 THE ARTISTIC ANATOMY OF ANIMALS
acromion process of the human scapula. The two regions separated by the spine are known as the supraspinous fossa and the infraspinous fossa. The supraspinous fossa is anterior to the spine, and the infraspinous is posterior to it. The surfaces of the scapula are, in quadrupeds, flatter than in the human being, and in particular the subscapular fossa, which is also less concave. Some authors attribute this to the lesser curvature of the ribs in quadrupeds. A few words
Fic. 14.—VERTICAL AND TRANSVERSE FG. 15.—VERTICAL AND TRANS- SECTION, AT THE SITE OF THE VERSE SECTION, AT THE PLANE SHOULDERS, OF THE THORAX OF THE OF THE SHOULDERS, OF THE HORSE (DIAGRAMMATIC FIGURE). THORAX OF A Doc (DIAGRAM-
1, Outline of the thorax at the level AE SCE of the third dorsal vertebra; 2, 2, 1, Outline of the thorax at the scapula; 3, spinal border of the levelofthe third dorsal vertebra; scapula ; 4, cartilage of prolongation; 2, 2, scapula; 3, spinal border of 5, contour of the skin. the scapula; 4, contour of theskin.
will suffice to prove that there must be another reason. The scapula is not in immediate contact with the ribs; the subscapular fossa is not moulded on them. Besides, the form of the scapula is, as in other parts of the skeleton, dependent on the disposition of muscles, and the develop- ment of these latter is correlated to the extent and energy of the movements which the individual is able or required
4
_ to execute. But the movements which those muscles _ produce (more especially the rotation of the humerus) are,
OSTEOLOGY AND ARTHROLOGY 25
in quadrupeds, less extensive than in the human being ; and, consequently, the muscles which produce them are, proportionally, less strongly developed. The inferior angle (superior and external in man), situated at the junction of the cervical and axillary borders, presents the glenoid cavity, which, looking downwards, receives the articular surface of the superior extremity of the bone of the arm— that is to say, the head of the humerus. Above this cavity, on the lower part of the cervical border, is situated a tubercle which reminds us of the coracoid process of the human scapula. The region occupied by the glenoid cavity is separated from the body of the bone by a constric- tion—the neck of the scapula.
In birds the scapula is elongated in a direction parallel to the vertebral column, and very narrow in the opposite (Fig. 18); it is also flat, and has no spine. Its coracoid process is represented by a peculiar bone—the coracoidean or coracoid bone—which we shall describe later on when we come to the study of the clavicle and of the anterior region of the shoulder (see p. 26).
The Clavicle.—The clavicle is found only in the human being, and in animals whose anterior limbs, possessing great freedom of movement in all directions, require that the scapula should possess a point of support which, while affording this, can be displaced with it, or draw it in certain directions. Now, this point of support is furnished by the clavicle.
In animals possessed of hoofs (ungulates), such as the sheep, ox, and horse, the clavicle does not exist. Indeed, in them the freedom of movement of the anterior limbs is limited ; they move by projection in the forward and backward directions only ; they merely fulfil the functions of giving support to and carrying about the body. The clavicle is rudimentary in the cat and the dog; in the cat it is a small, elongated bone (Fig. 16), 2 centimetres in length, thin and curved, connected with the sternum and the scapula by ligamentous bundles. In the dog it is
26 THE ARTISTIC ANATOMY OF ANIMALS
represented by a small osseous plate only (Fig. 17), which is not connected with any of the neighbouring bones.
It is on the deep surface of a muscle which passes from the head and neck to the humerus (mastoido-humeral, a muscle common to the arm, neck, and head) in which this
rudimentary bone is found to be developed.
The clavicle exists in perfect state in mammals which use their limbs for digging, grasping, or flying ; the insecti- vora (hedgehog, mole) and some rodents (squirrel, wood- — chuck) are provided with it. | |
The cheiroptera (bats) possess an extremely well-developed clavicle, on account of the varied movements which their thoracic limbs execute.
This formation of the shoulder. which javouus flight in the bat is even more remarkable in birds. In these latter
j
Fic. 16.—LEFT CLAVICLE OF THE Cat: FiG. 17.—CLAVICLE OF THE SUPERIOR SURFACE (NATURAL SIZE). Doc (NATURAL SIZE). 1, Internal extremity; 2, external ex- tremity.
(Fig. 18) the clavicles, fused together by their lower extremi- ties, form one bone, having the shape of the letter V or U, which is known as the fourchette ; this bone, acting as a true spring, keeps the shoulders apart, and prevents their approximation during the energetic movements which flight necessitates.
In birds whose power of flight is strong, the two limbs of this bone are widely separated and thick, and the four-
chette is U-shaped. Those whose flight is awkward and ~
but slightly energetic have the limbs of the fourchette slender ; they unite at a more acute angle, and the bone is Vv diane
Furthermore, a bone named the corvacoid joins the scapula to the sternum ; this bone, often fused with the scapula, where it contributes to the formation of the glenoid cavity, represents in birds the coracoid pzocess of the human
OSTEOLOGY AND ARTHROLOGY 27
scapula. If we fancy this process directed inwards, and sufficiently lengthened to join the sternum, we shall have an idea of the disposition of the bone we are now discussing, and the reasons for which the name has been chosen by which it is designated. The coracoid bone, like the fourchette
Eacuyen
Fic. 18.—SKELETON OF THE SHOULDER OF A BIRD (VULTURE): ANTERO- EXTERNAL VIEW OF THE LEFT SIDE,
1, Left clavicle ; 2, inferior portion of the right clavicle, forming by its ankylosis with that of the other side the fourchette; 3, coracoid bone ; 4, scapula; 5, articular surface for humerus; 6, superior half of the sternum ; 7, keel of sternum ; 8, spinous process of the dorsal vertebre ; g, superior ribs ; 10, process of one of these ribs; 11, inferior ribs.
which it reinforces, offers to the wings a degree of support proportionate io the efforts developed by those limbs ; for this reason it is thick and solid in birds of powerful flight. The superior extremity of each branch of the fourchette, at the level of its junction with the coracoid and the scapula, bounds, with these latter, a foramen which gives passage to
28 THE ARTISTIC ANATOMY OF ANIMALS
the tendon of the elevator muscle of the wing, or small pectoral. The importance of the fourchette being, as we have seen, in proportion to the movements of flying, it is easy to understand that the bone is not found in the ostrich.
The Arm
A single bone, the humerus, forms the skeleton of this portion of the thoracic limb. |
The Humerus.—-The bone of the arm is, in quadrupeds, inclined from above downwards and from before backwards.
It is, with relation to other regions, short in proportion as the metacarpus is elongated, and as the number of digits is lessened. In the horse, for example, whose metacarpus is long, and in which but one digit is apparent, the humerus is very short. The slight development in length of the humerus explains its close application to the side of the animal as far as the elbow.
In animals in which the humerus is longer, the bone is slightly free, as well as the elbow, at its inferior extremity. Later on we will return to the consideration of this peculiarity and of the proportions of the humerus, after we have studied the other parts of the fore-limbs.
The humerus in quadrupeds is inflected like the letter S ; in man this general form is less accentuated, the humerus being almost straight. On its body, which appears twisted on its own axis, we find the musculo-spiral groove,* which crosses the external surface, and is very deep in some animals. Above this groove, and on the external surface, there exists a rough surface which is the impression of the deltoid. In
* It would be going outside our province to discuss whether the humerus is really twisted on itsaxis. This question, often discussed, has been solved in some recent works in the following manner: the humerus has undergone torsion at the level of its superior extremity, and not at the level of its body ; this does not authorize us further to accord any definite sense to the denomination ‘groove of torsion’ (musculo-spiral groove). That which we must especially remember in connection with this fact, is, as we shall afterwards see, the difference of direction which the articular head presents according as the torsion has been more or less considerable: because this is established, according to the same order, in man and in quadrupeds.
Cuan «tale A -
OSTEOLOGY AND ARTHROLOGY 29
some species this rugosity is very prominent, and is called the tuberosity of the deltoid ; it is prolonged downwards by a border which forms the anterior crest of the musculo-spiral groove and limits this latter in front. The external border of the bone, or posterior crest of the groove, limits it behind.
The superior extremity is enlarged, and remarkable in three portions which it presents ; these are: an articular surface and two tuberosities.
The articular surface, or head of the humerus, smooth and round, is in contact ‘with the glenoid cavity of the scapula. This head in the human skeleton is directed upwards and in- wards ; in quadrupeds its direction is upwards and back- wards. The inferior extremity, having in both one and the other its long axis directed transversely, and the point of the elbow looking backwards in all, the result is that the head of the humerus is not situated vertically above the same regions ; in the first, it is almost directly above the internal part of this extremity; in the latter, it is situated above its posterior surface, or the point of the elbow in the complete skeleton. This difference of direction is corre- lated with the position of the scapula, the glenoid cavity of which, as we have already seen, is in man turned out- wards, whereas in quadrupeds it looks downwards. In the latter case the scapula consequently rests on the head of the humerus ; and this position is most favourable for the performance of the functions which the anterior limbs have to fulfil in these latter.
Of the tuberosities of the head of the humerus, one is situated on the external aspect—it is the great tuberosity, or trochiter ; the other is placed. internally—it is the small tuberosity, or trochin. The great tuberosity is divided into three parts—summit, convexity, and crest ; these different parts give insertion to the muscles of the shoulder. We recollect that the facets (anterior, middle, and posterior) of the great tuberosity of the humerus in man give attachment to the muscles of the same region. The head of the humerus in the human body projects above the tuberosities. We shall see afterwards, when dealing with some special quadru- peds, that in some of these, on the other hand, the tubero-
30 THE ARTISTIC ANATOMY OF ANIMALS
sities are on a higher level than the articular head of the bone. Between the two tuberosities is the bicipital groove.
In man, the superior extremity of the humerus, although covered by the deltoid, reveals its presence by elevating the corresponding portion of the latter. In quadrupeds, the anterior part of this extremity, although similarly covered by muscular bundles, produces a prominence under the skin. This prominence is situated at the summit of the angle formed by the opposing directions of the scapula and the bone of the arm, and constitutes what is known by the name of the point of the shoulder, or of the point of the arm.
The inferior extremity, transversely enlarged, presents an undulating articular surface, which reminds us of the trochlea and the condyle of the human humerus ; on which, how- ever, the condyle is more sharply defined from the trochlea.
In the human skeleton, the internal lip of the trochlea descends lower than the external ; and also lower than the condyle. In the bear, the cat, and the dog, it is the same. In the ox and the sheep, the condyle is lower than the trochlea, but only very little lower. In the horse the arrangement is still the same, but a little more accentuated.
On the lateral parts of this extremity we find : internally, a prominence, the epitrochlea; and, externally, another, the epicondyle. It is from this latter that the crest arises, which, passing upwards, forms the posterior limit of the groove of torsion.
The two prominences, which we have just described from a general point of view, present special arrangements which it is necessary to point out. When we examine the form of the outline of the inferior extremity of the humerus in man, the bear, the cat, the dog, the ox, and the horse, we find in following this order that the extremity tends to become narrow transversely, and that the epicondyle and the epitrochlea are less and less prominent on the external and internal aspects respectively. These two processes, indeed, project backwards; the epitrochlea always remain- ing more developed than the epicondyle. Because of this projection backwards, the cavity situated .on the posterior —
OSTEOLOGY AND ARTHROLOGY 31
surface of the inferior extremity, the olecranon fossa, is very deep, more so than in the humerus of man. Its borders being thus formed by the two processes, are very prominent. In front we find the coronoid fossa, which is less deep than
_ that of which we have just spoken.
_ There exists in some mammals an osseous canal, situated above the epitrochlea, and known as the supratrochlear canal (Fig. 19). It is bounded by a plate of bone which _ at its middle portion is detached from the shaft of the _ humerus, and blends with the latter at both its extremities.
ff re 4 Nasi
De aoe
. Fic. 19.—INFERIOR ExTREMITY OF Fic. 20.—INFERIOR EXTREMITY OF
THE LEFT HUMERUS OF A FELIDE THE Lerr Human HUMERUs,
(Lion). ; SHOWING THE PRESENCE OF A . ; SUPRATROCHLEAR PROCESS. 1, Epitrochlea ; 2, supra-epitrochlear foramen. 1, Epitrochlea; 2,supra-epitrochlear process.
| ; The brachial artery and median nerve pass through the
foramen.
A similar condition is sometimes found, as an abnormality,
in man, which presents itself under the following aspect
_ (Fig. 20): an osseous prominence more or less long, in the shape of a crochet-needle—supra-epitrochlear process—
situated 5 or 6 centimetres above the epitrochlea ; the
_ summit of this process gives attachment to a fibrous band, _ which is inserted by its other end into the epitrochlea and
_ the internal intermuscular aponeurosis. The fibro-osseous
ring thus formed gives passage to.the brachial artery and the:
32 THE ARTISTIC ANATOMY OF ANIMALS
median nerve, or in case of a premature division of this artery to the ulnar branch of the same.* , :
There is also found in some mammals a perforation of the thin plate of bone which, in others, separates the ole- cranon fossa from the coronoid. This perforation is some-— times found as an abnormality in the human humerus.
As does the sternum and the skeleton of the shoulder, the humerus of birds presents differences correlated to the functions which the thoracic limbs are destined to fulfil. Lying on the side of the thorax, directed obliquely down- wards and backwards (Fig. 21), it is proportionately longer in individuals of powerful flight than in those which fly less or not at all. In the vulture it projects beyond the © posterior part of the pelvis ; in the cock it does not even reach the anterior border of the same. To these differences in length are added differences in volume and in the develop- ment of the processes which serve for muscular attach- ment, which are more considerable in birds of powerful flight.
The humerus is so placed that the radial border, external in man and quadrupeds, looks upwards, with the result that the surface of the bone of the arm, which in these latter is anterior, in the former looks outwards. The humeral head, which is turned forwards and a little inwards, is convex and elongated in the vertical direction. Behind and above this head is found a crest for the insertion of muscles. It is the same for the region below, where there is a tuberosity whose inferior surface presents a pretty large opening which looks inwards to a fossa from the floor of which a number of minute openings communicate with the interior ofthe bone. This is the pneumatic foramen of the humerus.
It is of interest to remember in connection with this subject that in birds, in keeping with the conditions of flight, every system of organs is adapted to diminish the weight of the body. We particularly draw attention to the osseous framework, the structure of which is such that the weight
* For further details of this anomaly, see Testut, ‘ The Epitrochlear Process in Man’ (International Journal of Anatomy and Physiology, 1889) ; A. Nicolas, ‘ New Studies on the Supratrochlear Process in Man ’ (Review of Biology of the North of France, t. ili., 1890-1891).
OSTEOLOGY AND ARTHROLOGY 33
the animal is greatly lessened. This condition is secured by the pneumaticity. The bone consists of a cover of compact tissue, which, instead of enclosing marrow, is
Fic. 21.—SKELETON OF A BIRD (VULTURE): LEFT SURFACE.
_ 1, Cranium; 2, face; 3, cervical vertebre ; 4, spinous processes of i the dorsal vertebre ; 5, coccygeal vertebre ; 6, sternum; 7, keel; 8, _ superior ribs; 9, inferior ribs; 10, clavicle; 11, coracoid bone (for the _ details of the skeleton of the shoulder, see Fig. 18); 12, humerus; 13, radius; 14, ulna; 15, carpus; 16, hand (for details of the skeleton of _ this region, see Fig. 31); 17, ilium; 18, ischium ; 19, pubis (for the details _ of the pelvis, see Fig. 46); 20, femur; 21, tibia; 22, fibula ; 23, osseous nodule, which some anatomists think represents the calcaneum ; it is the sole vestige of the tarsus; 24, metatarsus ; 25, foot; 26, first toe (for
_ the details of the skeleton of the foot, see Fig. 48).
hollowed out by cavities which contain air, and communicate with special pouches, the air-sacs, which are appendages of _ the lungs.*
) * The presence of airin the bones does not seem to be always associated
_ with the power of flight ; as a matter of fact, we find air spaces in the bones of some birds which do not fly (E. J. Marey, ‘ The Flight of Birds,’ Paris,
1890, p. 51).
3
34 THE ARTISTIC ANATOMY OF ANIMALS
The antibrachial extremity of the humerus is flattened —
from without inwards. It terminates in two articular surfaces, which articulate with the radius and ulna.
The olecranen process cf the ulna being slightly developed, —
it follows that the olecranon fossa is not large ; neither is the coronoid.
General View of the Form of the Forearm and Hand
.
We now proceed to the study of the two regions of the ~
fore-limbs which present the greatest variety in regard to the number of bones and also in regard to form and pro- portions. These two regions are the forearm and the hand.
It is first of all necessary to say that in man, when the fore-limb hangs beside the body, and the dorsum of the hand looks backwards, the two bones of the forearm are parallel, and that this position is known by the name of supination. It is also necessary to remember that there is another attitude, in which the radius, crossing the ulna, and carrying the hand with it, displaces the latter in such a way that the palmar surface looks backwards. This second position is known as pronation.
:
Let us now suppose that a man wishes to walk in the © attitude of a quadruped. It will be necessary, in order that his upper limbs, being for the moment anterior ones, may act ~
as members of support, to place the forearm in pronation, in }
order that, as is more normal, the hands may rest on the ~
ground by their palmar surfaces. In this position the radius,
being rotated on its own axis at its upper extremity and — arcund the ulna in the rest of its extent, shall have its ©
inferior extremity situated on the inner side of the corre- sponding extremity of the latter.
Such is the situation of the bones of the forearm and the ~
attitude of the hand in quadrupeds. In short, quadrupeds :
have their anterior members in the position of pronation.
The individual whom we have just supposed placed in the — attitude of a quadruped would be able to maintain this — position by pressing cn the ground more or less extensive ~
portions of his hands; the whole palm of the hand may
be applied to the ground (Fig. 22); or the fingers only—
+ ¢
OSTEOLOGY AND ARTHROLOGY 35
that is to say, the phalanges (Fig. 23) ; or the extremities of the fingers only—that is to say, the third phalanges (Fig. 24). This last position, which is certainly difficult to maintain, should here be regarded rather as theoretical.
We shall meet with each of these modes of support in certain groups of animals. Thus, the bear, badger, and the
“majority of rodents, have the paws applied to the ground
by the whole extent of the palmar surface of the hand, from the wrist to the tips of the fingers. They are therefore called plantigrade, from the analogy, in this case, of the palm of the hand to the plantar surface, or sole of the foot.
|
Fic. 22.—THE Human HAND RESTING FOR ITS WHOLE EXTENT ON ITS : PALMAR SURFACE: LEFT SIDE, EXTERNAL SURFACE.
_ In others, such as the lion, tiger, panther, cat, wolf, and fox, the support is made no longer on the whole extent of the palmar surface, but on the corresponding surface of the fingers only—the metacarpus is turned back, and, conse- quently, the wrist—that is to say, the carpus—is removed from the ground. These are the digitigrades.
Lastly, the ruminants (sheep, oxen, deer, etc.), and also the pig, ass, and horse, rest on the third phalanx only. In them not only is the metacarpus turned back, but also the two first phalanges. The wrist is very far removed from
the ground. In these animals, the third phalanx is
enclosed in a case of horn, a nail (the hoof), and because Ke cre”
36 THE ARTISTIC ANATOMY OF ANIMALS
the support of the limb is on that nail, the name of unguli- grades has been given them. Nevertheless, as the point of support is on the third phalanx, which is also known by the name of phalangette, we are of opinion that, in order to” specify definitely, although they walk on their fingers, as’ do the digitigrades, the support is provided not by!the
Fic. 23.—THE Human HAND REsT- Fic. 24.—-THE HUMAN HAND REST ING ON ITS PHALANGES: LEFT ING ON THE TIPS OF SOME OF ITS SIDE, EXTERNAL SURFACE. THIRD PHALANGES: LEFT SIDE,
EXTERNAL VIEW. }
whole extent of those appendages, they might receive the name of phalangettigrades.
It is necessary among the ruminants to make an exception of the camel and the llama, which are digitigrades. |
Just in proportion as the hand is raised from the ground, as we have just seen in passing from the -plantigrades to the digitigrades and unguligrades, the number of bones of that. region diminishes, the bones of the forearm coalesce, and
OSTEOLOGY AND ARTHROLOGY ~:~ 37
the ulna tends to disappear ; the hand becomes less and less ‘suitable for grasping, climbing, or digging, so as to form an organ exclusively adapted for walking and supporting the body.
Thus, the bear (plantigrade) has five digits, and the power of performing the movements of supination and. pronation. Indeed, we know with what facility this animal is able to move his paws in every direction, and climb a tree by grasping it with his fore-limbs. It is well known, however, that no animal except the ape can perform the movements of rotation of the radius around the ulna with the same facility as man ; and that none possesses the same degree of suppleness, extent, and variety of move- ments of the forearm and hand.
In the digitigrades there is one finger which is but slightly developed, and which is always removed from the ground— that is, the thumb : there is also a little less mobility of the radius around the ulna.
In the ungulates the limbs are simply required to perform the movements of walking, and form veritable _ columns of support, which become the more solid as they are less divided. The bones of the forearm are fused together; there is therefore no possibility of rotation of the radius around the ulna. The metacarpus is reduced to a single piece, which in the horse consti- tutes what is known as the canon. The number of digits becomes diminished, so that in ruminants there are not more than two, and in the horse but one. We should, however, add that, up to the present, we have taken into account only perfect digits, those that rest on the ground. We shall see further on that there exist supplementary digits, but that they are only slightly developed, and are represented in some cases by mere osseous spurs ; it is this fact that has permitted us to ignore them in the general study which we have just made.
Because, as we have already said, the unguligrades have the inferior extremity of the digit encased in a horny sheath, which forms the hoof of the horse and the corresponding structures (onglons) in the ox, those animals have been
i:
38 THE ARTISTIC ANATOMY OF ANIMALS
placed in a special group, which is based on that peculi- arity—that is, the group of ungulate mammals.
The plantigrades and digitigrades, of which the paws have their surfaces of support strengthened by an epidermic sole and fatty pads, have the free extremities of the third phalanges covered on their dorsal surface by nails or claws ; hence they are named unguiculate mammals.
The bat and birds have the bones of the forearm so arranged that the radius cannot rotate around the ulna. This is necessary in order that during flight, when the wing is being lowered, the radius and hand shall not be able to turn ; for, if such rotation took place, each stroke of the wing would place it in a vertical position, which would occasion a loss of resistance incompatible with the effect to be obtained.
The Forearm
The skeleton of the forearm in quadrupeds is vertical in — direction ; consequently, it forms with the arm an angle open anteriorly ; this is well seen on examining the lateral surface. If we examine it on its anterior surface, we find a slight obliquity directed downwards and inwards. In animals in which the bones of the forearm are separate— — that is to say, susceptible of supination and pronation— we find a more close resemblance to those of the human ~ skeleton. The ulna, the superior extremity of which always projects beyond that of the radius, has a shaft which gradu- ally narrows from above downwards. Its inferior extremity is terminated by a round head in those animals in which the ulna is fully developed ; in others, as it is atrophied, it ends in a thin, long process.
The ulna presents at its superior extremity a posterior process, the olecranon, which forms the point of the elbow. We find on the anterior surface of the same, another process, the coronoid.
It is necessary to dwell on the relations of these parts. In man the head of the radius is situated at the anterior part of the external surface of the superior extremity of the ulna (Fig. 25) ; indeed, the small sigmoid cavity with which
OSTEOLOGY AND ARTHROLOGY . 39
the head articulates is situated on the outer side of the coronoid process, and this apophysis is placed in front. In the plantigrades and digitigrades the head of the radius is placed still more forward, so much so that it is situated almost in front of the superior extremity of the ulna (Fig. 26). In the unguligrades it is placed directly in front of this latter (Fig. 27).
Further, the displacement of the radius is made at the expense of the superior extremity of the neighbouring bone ; the radius appears to appropriate more and more the parts which in man belong exclusively to the ulna—for example, the coronoid process. In the plantigrades and the digiti-
Fic. 25.—-SUPERIOR EXTREMITY OF FIG. 26.—SUPERIOR EXTREMITY OF
THE BONES OF THE HUMAN ForE- THE BONES OF THE FOREARM OF ARM: LEFT SIDE, SUPERIOR SUR- THE Doc: LEFT LIMB, SUPERIOR FACE. SURFACE,
1, Radius; 2, ulna; 3, olecranon’ 1, Radius; 2, ulna; 3, olecranon process ; 4, coronoid process. process ; 4, coronoid process.
grades half of the process still belongs to the ulna and the remainder to the radius. In the ungulates—the horse, for example—the coronoid process belongs to the radius ; the ulna, situated behind the latter, is correspondingly dimin- ished in size.
In brief, when we study this region of the skeleton in plantigrades, then in digitigrades, and finally in unguligrades, . we find a kind of progressive absorption of one of the two bones (ulna) by the other (radius), which thus becomes the more developed.
It is easy to explain this partial disappearance of the ulna. When the forearm is capable of performing the
40 THE ARTISTIC ANATOMY OF ANIMALS
movements of pronation and supination, the ulna is com- pletely developed, for it is in its small sigmoid cavity that the head of the radius revolves, and it is around its inferior extremity, the head, that the corresponding extremity of the radius turns. But when the movements of rotation — of the forearm do not exist, the inferior extremity of the ulna becomes functionally useless and disappears. As to its rdle in the movements of the region of the wrist,
2
ae
Seaibt ste: eke
Fic. 27.—-SUPERIOR EXTREMITY OF THE BONES OF THE FOREARM OF THE Horse: LeErr LIMB, SUPERIOR SURFACE.
1, Radius; 2, ulna; 3, olecranon process ; 4, coronoid process.
that is nil, for we may remember—we will observe it again when we come to treat of the articulations—that the hand articulates with the radius alone (radio-carpal articulation) ; this is the reason that, when the forearm possesses the fullest mobility, the hand follows the movements which that bone makes around the ulna.
It is not so with the articulation at the elbow-joint ; there it is the ulna, which, with the humerus, forms the essential parts (humero-ulnar articulation); its olecranon process
OSTEOLOGY AND ARTHROLOGY 4I
i agers b 7
limits the movement of extension of the forearm. It is for _ this reason that, even in those quadrupeds in which the ulna
Fic. 28.—INFERIOR EXTREMITY OF THE BONES OF THE FOREARM OF A Man: Lert SIDE, POSTERIOR SURFACE, POSITION OF SUPINATION.
1, Radius; 2, ulna; A, groove for the long abductor and short extensor muscles of the thumb; B, groove for the radial muscles; C, groove for the long extensor of the thumb; D, groove for the special extensor of the index finger and of the common extensor of the fingers ; E, groove for the proper extensor of the little finger ; F, groove for the posterior ulna.
is atrophied, the olecranon process presents a relatively considerable degree of development. We know that on the posterior surface of the inferior
A nO ay ie Sy pea: Ma we
Fic. 29.—INFERIOR EXTREMITY OF THE BONES OF THE FOREARM OF THE Doc: LeErr SIDE, ANTERIOR SURFACE, NORMAL POosITION—THAT IS, THE POSITION OF PRONATION.
I, Radius; 2, ulna; A, groove for the long abductor and for the short extensor of the thumb; B, groove for the radials; D, groove for the long extensor of the thumb, the special extensor of the index-finger, and the common extensor of the fingers; E, groove for the special extensor of the little finger.
_ extremity of the bones of the human forearm are grooves _ in which pass the tendons of the posterior and external
42 THE ARTISTIC ANATOMY OF ANIMALS
muscles which, belonging to this region, are directed for insertion towards the hand.
In animals, because of the movement of rotation of the radius, the surface of this bone, which is anterior, corre- sponds to the posterior surface of the same in man. (To possess a clear conception of this, it is necessary to remember that, in this latter, the bones of the forearm are always described as in the position of supination ; they are thus represented in Fig. 28. The direction of the surfaces of the radius is the reverse of that in animals, since the latter have the radius always in a state of pronation.)
Consequently it is on the anterior surface of the bone that
A SB LB)
Fic. 30.—INFERIOR EXTREMITY OF THE BONE OF THE FOREARM OF THE Horse: Lert SIpE, ANTERIOR SURFACE.
1, Radius ; A, groove for the long abductor and the short extensor of the thumb ; B, groove for the radials ; D, groove for the common extensor of the digits ; E, groove for the special extensor of the little finger.
we find the grooves concerning which it is necessary to give some details. Regarding them in passing from the radius towards the ulna, those grooves give passage to the tendons of the muscles whose names occupy the columns on p. 43. — The letters which are referred to each serve to define their order, and to facilitate reference to Figs. 28, 29, and 30.
We should mention that the groove E is situated, both in man and in the dog, at the level of the inferior radio-ulnar articulation ; but that in the horse, as the ulna does not exist at that level, the groove is situated on the external surface of the inferior extremity of the radius. It is neces- sary to add that, in some horses, the ulna is, nevertheless,
| OSTEOLOGY AND ARTHROLOGY
Man.
Doc.
43
HORSE.
A. Long abductor of the thumb, and short ex- tensor of the thumb.
First and second external radials (extensor carpi vadialis lon- gioy and brevior). C. Long extensor of the thumb.
B.
D. Special exten- sor of the index finger and the common exten- sor of the fingers.
E. Special exten- sor of the little finger.
F. The posterior ulnar (extensor carpi ulnaris).
A. Long abductor of the thumb and short ex- tensor of the thumb united as one muscle, the oblique extensor of the metacarpus.*
B. The two radials blended superiorly, distinct inferiorly ; this is the anterior extensor of the metacarpus.
C. Long extensor of the thumb and special ex- tensor of the index finger united superi- orly. These muscles pass in the following groove,
D. Common extensor of the digits and the two preceding muscles,
E. Extensor of the third, fourth, and fifth digits, or the lateral extensor of the digits, the homo- logue of the special ex-
tensor of the little finger.
A. Oblique extensor of the metacarpus, the homo- logue of the long ab- ductor of the thumb and the short extensor of the thumb, united as one muscle.
B. The radials represented by a single muscle, the anterioy extensor of the metacarpus.
C. The long extensor of the thumb and_ the special extensor of the index are absent.
D. Anterior extensor of the phalanges, the homo- logue of the common extensor of the digits.
E. Lateral extensor of the phalanges, the homo- logue of the special extensor of the little finger.
There does not exist on the forearm a groove for the posterior ulnar muscle, or external flexor of the
metacarpus.
represented in this region by a tongue-like process of bone ; and in such cases the groove is situated in front of this process, at the level of the line of coalescence, which there
represents the articulation.
It is also useful to note, with reference to the groove F, in which passes, in man, the tendon of the posterior ulnar muscle, that, when the forearm is in pronation, the radius alone being displaced, we can only see this groove on the surface which looks backwards ; and that it is then separated from the groove which contains the tendon of the special extensor of the little finger by an interval equal to the thick-
* The words printed in italics are the names used in veterinary
anatomy,
4.4 THE ARTISTIC ANATOMY OF ANIMALS
ness of the head of the ulna.* When the forearm is supin- ated, the two grooves are found, on the other hand, one beside the other: and the tendons which they contain are very naturally in contact.
In birds the forearm is flexed on the arm, and the latter being directed downwards and backwards, the former is, consequently, directed upwards and forwards. Further, because of the position of the humerus, which, as we men- tioned on p. 32, has its inferior extremity so turned that the surface which is anterior in man becomes external, the radius, instead of being outside the ulna, is placed above it. This latter is larger than the radius, but its olecranon process is very slightly developed.
The Hand
The hand in animals, as in man, is formed of three parts— ~ the carpus, metacarpus, and fingers. In man, the forearm and the hand being described in the position of supination ; the bones of the carpus are named in passing from the most external to the most internal—that is to say, from that which corresponds to the radial side of the forearm to that which corresponds to the ulnar side. In animals in which, as we know, but it is not unprofitable to repeat, the hand is in pronation, the radial side of the forearm being placed inside, we enumerate the carpal bones in counting the most internal as the first ; this is the only method which permits us, in taking our point of departure frem the human skeleton as our standard, to recognise the homologies of the — bones of the carpal region. |
These bones, eight in number, are arranged in two trans- verse rows, of which one, the first, is superior or anti- brachial ; the other, the second, is inferior or metacarpal. Each of these rows contains four bones. Considered in the order we have indicated above—that is to say, proceeding from the radial to the ulnar side—they are thus named: scaphoid, semilunar, cuneiform, and pisiform, in the first
* Edward Cuyer, ‘ Shape of the Region of the Wrist in Supination and Pronation ’ (Bulletin de la Seciété d’ Anthropologie, Paris, 1888).
1 nes Toa Ol
OSTEOLOGY AND ARTHROLOGY 45
row ; trapezium, trapezoid, os magnum, and unciform, in the second. The number of these bones is not the same
in all animals on account of the coalescence or absence of
some. In each row the bones are placed side by side, with the exception of the pisiform, which being placed on the palmar surface of the cuneiform, produces a small pro- jection in man, but a very pronounced one in quadrupeds.
The pisiform is called the hooked bone in some veterinary anatomies. If we consider the hook which it forms, we may recognise that the name is appropriate; but from the point of view of comparison with the human carpus, the name is unfortunate, for it creates confusion between the true pisiform (the fourth bone in the upper row), and the last bone in the lower row, which is the veritable unci- form bone. We do not here seek for similarity of form, but homology of regions ; and it is only by using the same names to denote the same things that we can succeed in determining such homology.
Taken as a whole, the bones of the carpus form a mass which, by its superior border, articulates with the bones of the forearm, and by its inferior border is in relation with the metacarpal region. Its dorsal surface (anterior in quadrupeds) is slightly convex ; its palmar surface (pos- terior in quadrupeds) is excavated, and forms a groove in which pass the tendons of the flexors of the fingers. This last, in man, has the appearance of a gutter, because of the prominences caused by the projection of the internal and external bones beyond their fellows.
In quadrupeds the palmar groove is especially determined by the pisiform bone, of which we have just mentioned the great development.
The region occupied by the carpus, in the unguligrades, is known as the knee ; it would have been more appropriately named had it been called the wrzst.
The number of the metacarpal bones in mammals never exceeds five, but it often falls below it ; the same is true for the digits. The first are generally equal in number to the latter ; an exception is met with in ruminants, whose two metacarpals coalescing soon after birth, form but
46 THE ARTISTIC ANATOMY OF ANIMALS
one bone; this, the canon bone, articulates with two ~ digits. ;
The number of metacarpals and digits diminishes in pro- — portion as the limbs cease to be organs of prehension, and become more exclusively organs of support and locomotion.
The number of phalanges is two for the thumb and three ~ for each of the other digits; except in the cetaceans, in which they are more numerous.
In the bat, the metacarpals and phalanges are very long, and form the skeleton of the wing; these phalanges are — not furnished with nails ; the thumb, which is very short, is alone provided with one (Fig. 8).
With regard to the relative dimensions of the bones of the metacarpus, it is necessary to remember that, in the human being, the second metacarpal is the longest ; then, in the order of decrease, come the third, fourth, fifth, and first. In quadrupeds we shall also find differences in length (see the chapter relating to the anterior limbs in certain animals), but the order of decrease is not always that which we have just mentioned.
In man the articular surface, situated at the inferior ex- tremity of each of the metacarpals, is rounded, and is called the head. This allows the first phalanx, which is in relation with that surface, to be displaced in every direction ; indeed, this phalanx can not only be flexed and extended, but it can also be moved laterally ; this latter movement allows of the fingers being separated and drawn together.
In quadrupeds which can only perform the movements of flexion and extension of the digits—for example, the horse —the inferior extremity of the metacarpal has not a rounded head of a regular outline ; it is marked by a prominent median crest, directed from before backwards, so that the articular surfaces, which fit more exactly, form a sort of hinge which allows of backward and forward movements only, and permits no lateral displacement. In man, at the level of the inferior extremity of the first metacarpal, in the vicinity of the articulation of this bone with the first phalanx of the thumb, we find two sesamoid bones—small bones developed in
|
* on
7
-_
OSTEOLOGY AND ARTHROLOGY 47
the fibrous tissue which surrounds the articulation. We also meet with such structures, but more rarely, at the level
_of the corresponding articulation of the index and auricular
digits ; and, more rarely still, at those of the middle and ring fingers. In quadrupeds, these bones are normally
_developed, and we shall see afterwards that in some
animals, as they reach a considerable size, they are able to
_ influence the external outlines ; we shall see this, for example,
an +
in the horse. The hand, in birds, is directed obliquely downwards and backwards (Fig. 31). For the better understanding of its
Fic. 31.—SKELETON OF THE SUPERIOR LIMB OF A BIRD (VULTURE): LEFT SIDE, EXTERNAL SURFACE.
1, Humerus ; 2, radius; 3, ulna; 4, radial bone of the carpus; 5, ulnar bone of the carpus; 6, first metacarpal; 7, second metacarpal ; 8, third metacarpal ; 9, first digit, the homologue of the thumb ; 10, first phalanx of the second digit ; 11, second phalanx of the second digit ; 12, third digit. position in relation to the forearm, we should remember that this latter, as we have described (p. 44), directed obliquely upwards and forwards, has the radius placed above the ulna; the hand being oblique in the opposite direction and placed under the forearm is, by this arrange- ment, inclined towards the ulnar border of the latter.
For the rest, in order to be able to distinguish readily the corresponding parts in the hand of a bird and that of a man, we merely have to place the human forearm obliquely, in a direction upwards and forwards (Fig. 32), the radius being above ; this position we can obtain by semi-pronation ;
ened
48 THE ARTISTIC ANATOMY OF ANIMALS
—ae!
then, to incline strongly the hand downwards and back-_ wards, moving the ulnar border of the hand towards the ulna; the thumb is then anterior, the little finger — posterior, and the palm of the hand is turned towards the trunk.
The carpus in birds is formed by two bones only, with which the skeleton of the forearm articulates. That which is in contact with the radius is called the radial bone of the carpus ; and that with which the ulna articulates — is named the ulnar bone. |
The metacarpus is formed of three bones; the first, which is very short, is fused at its superior extremity with ©
uae,
ee ee
PIG. 32.—SUPERIOR LIMB OF THE HUMAN BEING, THE DIFFERENT ~ SEGMENTS BEING PLACED IN THE ATTITUDE WHICH THE CORRE- ~ SPONDING PARTS OCCUPY IN BIRDS: LEFT SIDE, EXTERNAL SURFACE.
the adjoining one; this latter and the third, both longer than the first, but of unequal size, are fused at their extremities. The metacarpal, which articulates with the radial bone of the carpus, is larger than the one which is in line with the ulna. To the metacarpus succeed three digits, of which the central is the longest, and is formed of two phalanges ; the other two are formed each by a small, stylet-shaped bone. The middle finger, situated on the prolongation of the metacarpal, which articulates with the radial bone of the carpus, has its first phalanx large and flattened transversely ; this phalanx seems to have been formed by the union of two bones of unequal development; the second phalanx ~
OSTEOLOGY AND ARTHROLOGY 49
s styloid in form. As to the other two fingers, they are ‘placed, one in front and the other behind ; the first, which articulates with the short metacarpal, fused at its upper end with the principal bone of the metacarpus, in position ‘represents the thumb. The other, which is the third é fi ger, articulates with the inferior extremity of the thinnest bone of the metacarpus; it is sometimes closely united o the corresponding border of the first phalanx of the ri _ —that is to say, of the median—digit.
The Anterior Limbs in Certain Animals
| i Plantigrades : Bear (Fig. 33).—The scapula of the bear ‘approaches in shape to a trapezium, of which the angles have been rounded off. The anterior border (cervical) is strongly convex in the part next the glenoid cavity. The junction of the superior (spinal) and the cervical border forms almost a right angle, the summit of which corre- _ sponds to the origin of the spine. At its posterior angle there is a prominence, directed downwards, the surface of ' which is hollowed and is separated from the infraspinous fossa by a crest, so that at this level a third fossa is added to the infraspinous one. The neck of the scapula is but slightly “marked. The acromion is prominent, and projects a little. eyond the glenoid cavity. _ The clavicle is rudimentary, but, as an example of the _ complete development of this bone in plantigrade quadru- _ peds, we may cite the marmoset. __ The humerus is furnished at its superior extremity with a large tuberosity, wide, and situated in front of the head of - the bone ; the effect of this is that the bicipital groove is internal. As in man, the great tuberosity does not reach so high as the humeral head, but it approaches more nearly te that level. The deltoid impression is very extensive, , and descends pretty far down on the body of the bone. The epitrochlea is prominent ; the epicondyle is surmounted by _ a well-marked crest, curved and flexuous in outline. _ The articular surface, which is in contact with the _ fadius, is not a regularly formed condyle; it is a little 7. 4
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THE ARTISTIC ANATOMY OF ANIMALS
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OSTEOLOGY AND ARTHROLOGY 51
flattened on its anterior surface, and presents at this level a slight depression which corresponds to a small eminence on the anterior aspect of the superior extremity of the radius. The surface which articulates with the ulna, viewed on its anterior aspect, has the shape of a slightly-marked trochlea ; except at the level of the internal lip, which, as in man, descends lower than the surface for articulation with the radius (condyle). Behind, the trochlea is more clearly defined.
The bear possesses a considerable power of rotation of the radius ; the bones of the forearm are joined only at their extremities, while in the remainder of their extent they are widely separated. The ulna terminates below in a head and a styloid process; these articulate with the two last bones of the first row of the carpus—viz., the cunei- form and pisiform. The bones of the carpus are seven in number, the scaphoid and the semilunar being fused together.
The metacarpals, five in number, differ very little from one another in regard to length, though they increase in size from the first to the fifth ; this may be demonstrated by looking at the palmar surface of the hand. It is the reverse of that which we find in man, for the fifth meta- carpal is the thickest of all, and the first is the most slender.
At the level of each USE Meh articulation are two sesamoid bones.
The third digit is the longest. The terminal phalanges present two very different portions: one, the anterior, is curved and pointed ; it serves to support the nail, whose shape it assumes; the other, posterior, forms a sort of sheath into which the base of the nail is received.
The inferior portion of the posterior surface of this latter part articulates with the second phalanx in the case of each of the last four digits, but with the first phalanx in the case of the thumb.
Digitigrades: Cat, Dog (Fig. 34).—In these animals the anterior (cervical) border of the scapula is convex; the posterior (axillary) border is straight or slightly concave.
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THE ARTISTIC ANATOMY OF ANIMALS
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The supraspinous and infraspinous fossze are of equal extent (Figs. 35 and 36). The neck is short. The spine ofjthe
A
Fic. 35.—SCAPULA OF THE Doc: LEFT SIDE, EXTERNAL SURFACE.
1. Posterior or axillary border ; 2, superior or spinal border ; 3, anterior or cervical border ; 4, spine of scapula ; 5, coracoid process ; AA}, length of spinal border.
scapula becomes more and more prominent towards its inferior extremity, where it ends in a twisted and inflexed portion, which represents the acromion process ; this pro-
A
Fic. 36.—LEFT SCAPULA OF THE CaT: EXTERNAL SURFACE.
1, Posterior or axillary border ; 2, superior or spinal border ; 3, anterior -or cervical border; 4, spine of the scapula; 5, coracoid process; AA}, length of the spinal border.
cess terminates at the level of the glenoid cavity. The coracoid process is represented by a small tubercle, slightly
54 THE ARTISTIC ANATOMY OF ANIMALS
curved inwards ; this tubercle is situated above the glenoid cavity, at the inferior part of the cervical border.
In the dog, the posterior angle, formed by the junction of the axillary and the superior (spinal) borders, is obtuse ; the spine rises perpendicularly from the surface of the bone. The width of the scapula, measured at the level of the spinal border (from A to A’, Fig. 35), equals about half the length of the spine. We must, however, make an excep- tion for the turnspit dog, in which the superior border equals three-fourths of that length. The scapula is, in this case, of a more compact type; it is broader, but shorter. In the cat, the anterior outline of the scapula, formed by the union of the cervical border and the corresponding half of the spinal, is more convex; the posterior angle is not obtuse, as in the dog. The spine is bent slightly down- wards and backwards; before terminating in the acro- mion process it presents a triangular projection, the apex of which is directed downwards. The tubercle which re- presents the coracoid process is curved inwards more strongly than that of the dog, thus resembling more closely the appearance of this process in the human being.
All proportions considered, the scapula of the cat is broader than that of the dog; its width, measured along the length of its spinal border (from A to A’, Fig. 36), equals three-fourths of the length of the spine.
The clavicle is rudimentary ; it is, however, better de- » veloped in the cat than in the dog. The clavicle of the cat is represented by a small, elongated bone, curved in out- line, the convexity being turned forward ; it is united to the acromion and the sternum by ligamentous fibres ; that of the dog is merely a scale-like osseous plate situated on > the posterior surface of a muscle of this region (see Figs. 16 and 17).
The humerus is long and twisted in the shape ofan S. The inferior articular surface has the form of a simple pulley, for the condyle is very slightly marked. The internal part of this articular surface descends lower than the external ; this condition resembles that found in the human being,
OSTEOLOGY AND ARTHROLOGY 55
where the inner lip of the trochlea is lower than the condyle.
In the dog, the olecranon fossa communicates with the coronoid by an opening.
In the cat, there is a supra-epitrochlear canal (see Fig. 19), but no olecranon perforation.
The bones of the forearm articulate at their extremities. The body of the radius is united to the body of the ulna by a short, thick, interosseous ligament; the fibres of this ligament, though short, do not prevent the production of some movements at the articulations of the bones.
The radius so crosses the ulna that above, it is in front and external to the latter, while below, it is internal. This bone is flattened from front to back, and slightly convex anteriorly. Its superior extremity is formed, externally, of a portion which represents the head of the radius in man; internally, by another portion which represents half of the coronoid process of the ulna, which, in the human being, belongs exclusively to the latter (see p- 39, the encroachment of the radius on the ulna). This extremity is surrounded with a vertical articular surface which is placed in contact with a small cavity which is hollowed out on the ulna (the lesser sigmoid cavity); and presents at its superior aspect a surface which articulates with the inferior extremity of the humerus. The shaft of the bone has on its internal border rugosities analogous to the imprint of the pronator radii teres of the human skeleton ; these rugosities, indeed, give insertion to a muscle of the same function, and bearing the same name. The inferior extremity, broader than the superior, is hollowed on its external aspect by a small cavity which receives the in- ferior extremity of the ulna; its inferior surface (concave) articulates with the carpus ; its anterior surface (the homo- logue of the posterior surface of the corresponding extremity of the human radius) presents grooves which serve for the passage of the tendons of the muscles which pass from the forearm to the back of the hand. (For the names of the muscles whose tendons pass in these grooves, see Fig. 29.)
56 THE ARTISTIC ANATOMY OF ANIMALS
The ulna is furnished at its superior extremity, with an olecranon process, which is more prominent than that of the human ulna ; this process is compressed laterally, and its internal surface is hollowed ; there we also find a great sigmoid cavity, and a coronoid process situated at the internal part of the anterior surface, a process which, as we have previously shown, it shares with the radius.
The shaft of the bone, prismatic and triangular, diminishes in thickness as it approaches the lower extremity, which articulates with the corresponding extremity of the radius. In the dog, the ulna terminates inferiorly in a blunt point, without enlargement, analogous tc the head of the human ulna ; in the cat, by a head which is prolonged into a styloid process, by which it articulates with a portion of the carpus.
The carpus consists of seven bones—three in the superior row and four in the inferior. In the superior row the scaphoid and semilunar bones are fused together. The pisiform is elongated and expanded at its two extremities ; it forms a prominence which, directed backwards, projects beyond the level of the other bones of this region.
The metacarpal bones are five innumber; they are enume- rated from within cutwards; they articulate with the carpus and with each other. The inferior extremity of each meta- carpal bone presents the form of a condyle in front ; and is divided behind so as to form two lateral condyles, which are separated by a median crest ; on these posterior condyles are applied two small sesamoid bones. The metacarpal bone of the thumb is very short ; the third and fourth are the longest. The metacarpus, as a whole, is directed verti- cally.
The phalanges are three in number for each finger, except the thumb, which has but two. The first phalanx, directed almost horizontally forwards, is the longest ; the second is directed downwards and forwards; the third consists of two portions : a posterior part, which forms a sort of sheath into which the base of the nail is received ; and an anterior, conical in form, and curved in crochet shape, which forms a support for the nail (Fig. 37).
OSTEOLOGY AND ARTHROLOGY 57
The third and fourth digits are the longest ; the second and fifth are of equal length; the thumb is the shortest ; it does not touch the ground, and does not even reach the articulation of the metacarpal bone and first phalanx of the second finger. 7
In the cat, the metacarpal bone of the thumb, although shorter than any of the others, is quite as thick. The third digit is a little longer than either the second or fourth. In animals of this genus, the claws, in the condi- tion of repose, are retracted, and removed from the ground ; this prevents their being worn, and thus pre-
Fic. 37.—SKELETON OF THE FINGER OF A FELIDE (LION): LEFT SIDE, INTERNAL SURFACE.
1, Metacarpus ; 2, sesamoid bones ; 3, first phalanx ; 4, second phalanx ; 5, third phalanx ; 6, gutter for the reception of the base of the nail; 7, prominent osseous crest formed to lodge in the concavity of the nail.
serves their sharpness. At such times the third phalanx is received into a groove which is found on the external surface of the second phalanx. In the dog, the claws are not tractile.
Unguligrades: Pig (Fig. 38).—The scapula is markedly narrowed in the region above the glenoid cavity. The spine is atrophied at both its extremities, so that at its inferior part we do not find the acromion process. In its middle portion the spine is prominent, and presents a triangular process which turns backwards, overlapping a part of the infraspinous fossa ; this latter is much larger
THE ARTISTIC ANATOMY OF ANIMALS
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OSTEOLOGY AND ARTHROLOGY 59
than the supraspinous. The spinal border is surmounted by the cartilage of prolongation, the superior margin of which is convex ; this cartilage extends posteriorly beyond the posterior (axillary) border of the bone.
The small tuberosity of the superior extremity of the humerus is but slightly developed ; the great tuberosity, on the contrary, is very large. The bicipital groove is situated internal to this. The deltoid impression is scarcely marked.
The forearm is short, directed obliquely downwards and inwards, thus forming with the hand an angle, of which the apex is directed inwards. The two bones of the forearm are strongly bound to one another by an interosseous liga- ment, which is formed of very short fibres. The radius appropriates, at its superior extremity, the coronoid process of the ulna. The latter is, notwithstanding, well developed in the rest of its extent; it has a flattened shaft which almost completely overlaps the posterior surface of the radius ; its inferior extremity reaches to the carpus.
The carpus is formed of eight bones—four in the superior row, and four in the inferior. The third bone of the superior row (cuneiform) is more in contact with the ulna than with the radius.
There are but four metacarpal bones ; there is no meta- carpal of the thumb. The two median metacarpal bones are the longest ; they are those which correspond to the digits which alone touch the ground. The internal digit and the external one are thin and short ; they are function- less, as a rule, taking no part in supporting the limbs on the ground. Notwithstanding this, they are formed, as the other digits, of a number of phalanges, which give them the semblance of perfect digits. (We shall soon see that in certain animals there exist digits which, being in- complete with regard to the numbers of their constituent bones, more accurately merit the name of imperfect digits.)
The third phalanges are each enclosed in a horny hoof, to which the name of onglon has been given.
We have already drawn attention to the smaller lateral
60 THE ARTISTIC ANATOMY OF ANIMALS
digits, and noted the general fact that they do not come in contact with the ground. It is necessary to modify this statement by adding that under certain conditions they give a slight amount of support ; for example, when the individual is the subject of excessive obesity, the limbs yield under the weight, and the nails of the lateral digits may touch the ground.
A similar fact may be noticed in pigs of ordinary bulk at the moment when, during walking, each of the fore-limbs commences to bear the weight—that is to say, when it is directed obliquely downwards and forwards; then all the digits are in contact with the ground.
Unguligrades (Ungulates): Sheep, Ox (Fig. 39).—The scapula, which is of elongated form, is very narrow in the vicinity of the glenoid cavity. The spine, which becomes more and more salient towards its inferior part, terminates abruptly in a border, which, forming an acute angle with the — crest, produces a projection which represents the acromion process—a very rudimentary acromion, for it does not reach the level of the glenoid cavity. The supraspinous fossa is much smaller than the infraspinous; it hardly equals one- third the extent of the latter. Theanterior border, thin and convex in its superior portion, is concave in the rest of its extent ; the posterior border is thick and slightly concave ; the spinal bcrder is surmounted by the cartilage of pro- longation. In the ox the spine of the scapula, in its middle portion, is flexed a little backwards on the infraspinous fossa. :
The great tuberosity of the humerus is highly developed ; — its summit, very prominent, is flexed over the bicipital groove ; a prominence of the small tuberosity also bends over the groove, with the result that at this level the latter is converted into a sort of canal. At the inferior extremity the condyle, although not large, is recognisable ; for it is separated from the trochlea by a depression in form of a groove. In contrast to the condition found in man, the condyle descends to a level a little below that of the in- ‘ternal lip of the trochlea. (For the arrangement of the epicondyle and the epitrochlea, see p. 30.) In the sheep,
61
OSTEOLOGY AND ARTHROLOGY
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62 THE ARTISTIC ANATOMY OF ANIMALS
the deltoid impression is but slightly marked ; in the ox, it is more evident.
The forearm is directed obliquely downwards and in- wards, so as to form, with the hand, an angle of which the apex is internal ; this angular outline of the knee (wrist) is so characteristic of ruminants that the corresponding region of the horse, when salient inwards, receives the name of ox-knee. The radius bears the coronoid process, and the larger part of the articular surface which comes in contact with the inferior extremity of the humerus ; the condyle and the trochlea articulate with the radius in front ; while behind, the trochlea articulates with that part of the sig- moid cavity which belongs to the ulna. The posterior surface of the shaft of the radius is flattened ; its anterior
surface is slightly convex. The inferior extremity articu-
lates with the carpus by a surface which is directed obliquely downwards and inwards. The shaft of the ulna is very slender, and fused in its middle third with the body of the radius ; it terminates below, at the level of the external part of the inferior extremity of the radius, by a slightly expanded portion which, fused with this latter, forms the articular surface for the carpal bones.
In the ox the forearm is short ; in the sheep it is propor- tionally longer.
The bones of the carpus are six in number—four in the upper row, and two in the lower; they form an irregular cuboid mass which contributes to the formation of the region known as the knee in ruminants, as in the horse ; we have already remarked that the name ‘wrist’ would be more accurate. The anterior surface in its foremost part is vertical, and is slightly convex from side to side. At its posterior and external part the pisiform bone forms a pro- minence.
The metacarpus consists of two bones only—one, well developed, which is known as the principal metacarpal, or the canon bone (this is the name given to the region in the hoofed animals) ; and a rudimentary one, which is situated at the superior and external aspect of the preceding meta- carpal. Sometimes there is found a third metacarpal
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OSTEOLOGY AND ARTHROLOGY 63
at the internal aspect; but, when present, it is but very slightly developed.
The principal metacarpal consists of two metacarpals fused together ;-on this account the bone is longitudinally marked in the median line by a slight depression which marks the junction of the two bones of which it is formed. In some ruminants (certain species of chevrotains) the coalescence does not take place, and the two meta- carpals remain separate.
The anterior surface of the principal metacarpal is convex transversely ; its posterior surface is flattened. The superior extremity of this bone articulates by two facets with the two bones of the inferior row of the carpus ; on the internal part of the anterior surface of this extremity is found a tubercle. The inferior extremity is divided into two parts by a fissure or notch; each part is articular, and consists of two separate condyles, which are separated from each other by an antero-posterior crest ; on each side of this crest, and behind, are found two sesamoid bones. As for the external rudimentary metacarpal bone, it is nothing more than a small, short tongue of bone; which, in goats and sheep, is often absent.
The division of the inferior extremity of the principal metacarpal into two parts is correlated with the two perfect digits which give the foot of the ruminant its forked appear- ance. Each digit consists of three phalanges, which are directed obliquely downwards and forwards ; further, these phalanges are inclined a little outwards from the axis of the limb, so that the two digits diverge from each other as they descend.
The first phalanx, which is the longest, articulates superiorly with the principal metacarpal; its inferior extremity terminates in a trochlea, and the lip of this, which is situated towards the axis of the limb, descends lower than that of the opposite side ; this arrangement is correlated with the divergent direction of the digits. The second phalanx has its superior extremity moulded on the trochlea which terminates the extremity of the first ; its inferior extremity is articular, and elongated from before
64 THE ARTISTIC ANATOMY OF ANIMALS
backwards. On the posterior surface of this extremity is found a sesamoid bone. :
With regard to the third phalanx, it presents the form of a triangular pyramid, and displays a postero-superior concave surface with which the second phalanx articulates ; an anterior, convex surface, which terminates in a point on its anterior part; and an internal surface, which is flattened. The third phalanx of each digit is contained in a hoof (onglon).
There is also found in ruminants two imperfect rudimen- tary digits, which are represented by two small bones situated behind the articulation of the metacarpal and the digits which we have just been studying. These rudi- mentary digits are each enveloped in a layer of horn ; they constitute the spurs. The two digits of the ruminants represent the third and fourth fingers of the human hand ; the two lateral digits, greatly atrophied, are the homo- logues of the second and fifth fingers; the thumb is not present. ,
It is the same as regards the metacarpal bones, which form, by their union, the principal metacarpal ; the external repre- sents the fourth metacarpal, and the internal the third. It is. to the latter that the tubercle, of which we have already made mention, belongs ; and with the signification of which, because it gives attachment to a muscle, we shall concern ourselves in the section on myology (see Radial Muscles). __
Unguligrades: Horse (Fig. 40).—The scapula is narrow, compared with that of the animals we have just been con- sidering. The anterior border is convex in its superior portion, and concave in its inferior ; the posterior border is slightly hollowed out. The supraspinous fossa is less in extent than the infraspinous ; but the difference is less than that between the same fossz in the ox and the sheep; in the ox, as we have already indicated, the proportion is one- third ; in the horse, one-half. The spine, which disappears at the extremities, is rough and thick in its middle third, there forming a kind of tuberosity—tuberosity of the spine. Above and in front of the glenoid cavity is found a strong process consisting of a rugous base, and a summit which is
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Fic. 40.—SKELETON OF THA,
1, Cranium; 2, face; 3, atlas; 4, axis; 5, seventh cervical vertebra; 9, Sacrum ; 10, coccygeal vertebrae ; 11, sternum; 12, xiphoidl appendix ; of extension ; 17, great tuberosity of the humerus; 18, deltoid crest; 19, cfrap 24, metacarpal, external rudimentary ; 25, large sesamoids; 26, first phn; fossa ; 30, pubis ; 31, tuberosity of the ischium; 32, great trochanter ; femur; 35, knee-cap; 36, anterior tuberosity of the tibia; 37, the fibula ; external metatarsal ; 42, large sesamoids ; 43, first phalanx ; 44, second ;
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)irst dorsal vertebra; 7, eighteenth and last dorsal vertebra; 8, lumbar vertebre ;
eighteenth and last sternal rib; 14, costal cartilage; 15, scapula; 16, cartilage ljranon process; 20, radius ; 21, carpus; 22, pisiform; 23, principal metacarpal ;
x}; 27, second phalanx; 28, third phalanx; 29, ilium, showing external iliac 3)infratrochanteric crest, or third trochanter; 34, supracondyloid fossa of the , tarsus astragalus; 39, calcaneum; 40, principal metatarsal; 41, rudimentary lanx ; 45, third phalanx.
To face p. 64.
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OSTEOLOGY AND ARTHROLOGY 65
directed inwards. This forms a kind of hook curved towards the inside; it represents the coracoid process.
_ The scapula is surmounted by the cartilage of prolonga-
tion, of which the superior border, which is thin and curved, is parallel to the superior border of the prominence of the withers ; the cartilage forms, consequently, the lateral surface of this region. The cartilage of prolongation undergoes ossification in old horses. The humerus is short ; the bicipital groove, situated on the anterior surface of the
‘superior extremity, separates the greater tuberosity from
the lesser, and is divided into two parts by a median ridge ; it is this portion of the humerus which forms the prominence known as the point of the shoulder, or point of the arm. The deltoid impression well deserves the name of tuberosity which has been given to it, for it is very prominent ; the musculo-spiral groove is very deep.
At the inferior extremity, the trochlea is large; the portion corresponding to the condyle of the humerus in man is, in proportion to the latter, of small extent. The olecranon fossa is deep. The epicondyle and the epitrochlea
are somewhat different from those of the human bone. In
the latter, the epitrochlea is salient towards the inner side, causing an increased transverse diameter of the inferior extremity of the humerus. In the horse—it is the same in ruminants—this tuberosity projects backwards, folds on itself in forming the internal boundary of the olecranon cavity, and exceeds in diameter, in the antero-posterior direction, the prominence of the epicondyle, which presents a nearly similar arrangement. This latter has, however, a_ part
-which, projecting externally, is situated at the inferior
part of a crest, that forms the posterior boundary of the musculo-spiral groove. The result is that, contrary to the condition found in the human being, the epicondyle is more prominent transversely than the epitrochlea, but this latter is more salient on the posterior aspect. The epitrochlea and the epicondyle offer a larger surface for the origin of muscles of the forearm than the same prominences in the human bone do for. the analogous muscles of the same region. 5
66 THE ARTISTIC ANATOMY OF ANIMALS
Some veterinary anatomists have given to the inferior and external articular surface of the humerus the name of trochlea ; and to the internal one, that of condyle. On this account they designate the external prominence as the epitrochlea, and the internal one as the epicondyle. In addition to the fact that this point of view is not legitimate, it produces inevitable confusion when comparing the parts with those of the human humerus, and this confusion exists, not alone in describing the bone, but also in the description of the muscular attachments, and in the comparison of the muscles of the forearm of quadrupeds with the correspond- ing muscles in the human species.
The radius is placed in front of the ulna; its body, slightly convex forwards, has the anterior surface convex transversely, and the posterior surface plane in the same direction. It is to the external part of this latter that the ulna is applied, which is completely fused with the radius.
The superior extremity of the radius is a little larger than the inferior. Its superior aspect, concavo-convex, moulded -on the inferior articular surface of the humerus, presents internally two cavities, which receive the lips of the trochlea,
and, externally, another, smaller, cavity, which receives the
condyle. The radius articulates with the trochlea and the condyle, having appropriated a portion of the ulna, as is proved by the presence of the coronoid process, which belongs to the former. This superior extremity presents, internally, a tuberosity into which the biceps is inserted ; this is the bicipital tuberosity ; and on the other side is another tuber- osity, which is a little more prominent than the preceding. The inferior extremity, which is flattened from before backwards, is furrowed on its anterior surface by grooves for the passage of muscles (the names of the muscles whose tendons pass in these grooves have already been given on p- 43). It articulates at the lower end with the superior row of the carpus, and it terminates laterally in tuberosities : one, external, on which is found a groove for the tendon of the lateral extensor of the phalanges, the homologue of the special extensor of the little finger; the other, internal, is a little more prominent than the one we have just described.
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OSTEOLOGY AND ARTHROLOGY 67
These tuberosities are visible under the skin which covers
_ the superior and lateral parts of the region known as the
knee ; but which, we again repeat, is no other than the wrist.
The ulna has a triangular shaft, situated at the posterior surface of the radius, with which it is fused. It disappears completely at the level of the inferior third of the forearm. Occasionally, in some horses, the ulna is abnormally long, in the form of a slender tongue of bone ; and extends to the neighbourhood of the external tuberosity of the inferior extremity of the radius (see Fig. 79, p. 196). Its superior extremity is chiefly represented by the olecranon process, which is voluminous in bulk, and forms the projection known as the point of the elbow. This process is flattened laterally ; its internal surface is excavated ; the anterior surface, which is concave, forms a part of the great sigmoid cavity ; the remainder of the cavity is formed by the radius.
In the ass, the ulna is a little longer than in the horse— that is to say, it descends lower ; and the radius is a little more convex anteriorly.
The carpal bones are seven in number—four in the superior row, and three in the inferior. The trapezium is wanting in the latter. Sometimes, however, in certain varieties of horses the trapezium is developed, but then it isno more than a very
small osseous nodule. The pisiform bone, situated at the .
external part of the first row of bone, is prominent pos- teriorly. It is of rounder form and flattened from without inwards. It articulates with the trapezium and the radius. It presents, on its external surface, a groove for the passage of the tendon of the posterior ulnar muscle, which is named by veterinary anatomists the external flexor of the metacarpus. The carpus, as a whole, is of an irregularly cuboid shape ; its anterior surface, slightly convex from side to side, forms
the skeleton of the region of the knee (wrist). The meta-
carpus is formed of three bones: the principal metacarpal and the two rudimentary ones.
The principal metacarpal, which forms the region of the canon, is directed vertically ; its anterior surface is slightly convex transversely. This surface is covered by a number
5—2
6 THE ARTISTIC ANATOMY OF ANIMALS
of tendons, which slightly alter its appearance ; so that it is — : the principal base of this part of the fore-limb. Its posterior
surface is flattened. The superior extremity of this metacarpal presents plane surfaces, variously inclined, with which the
bones of the inferior row of the carpus articulate. On the |
anterior surface, and a little to the inner side, is found a tuberosity, which is destined for the insertion of the anterior extensor of the metacarpus, the hcmologue of the radial muscles. The inferior extremity is formed by two condyles, an internal and an external; between which is found a median crest.
This extremity, the superior extremity of the first phalanx, which articulates with it, together with two sesamoid bones —the great sesamoids—which are situated on its posterior
surface, collectively form the region which from its rounded —
outlines is called the ball.
With regard to the rudimentary metacarpals, external and internal, to which some authors give the name of fibula, they are applied to the sides of the posterior surface of the principal metacarpal. They are elongated bones, of which the superior extremity, which is a little thickened, is called
the head ; the lateral bones of the second row of the >
carpus partly rest on the heads of these. They become more slender as they descend, and terminate opposite the inferior fourth of the principal metacarpal. Each ends in a slight swelling, to which the name button has been given. The internal one is the better developed.
The rudimentary metacarpals are vestiges of atrophied digits, as will be explained further on.
The single finger of the horse consists of three phalanges. The first phalanx, which is directed obliquely downwards and forwards, corresponds to the constricted region situated below the ‘ ball,’ and known as the pastern. It is flattened from before backwards ; its anterior surface is convex trans- versely, while the posterior surface is plane. Its superior extremity is moulded on the inferior extremity of the principal metacarpal, and its inferior extremity, which is smaller, presents a trochlea with which the second phalanx articulates. This is also directed downwards and forwards,
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OSTEOLOGY AND ARTHROLOGY 69
and is shorter. It corresponds to the region which, situated between the pastern and the hoof, is known as the cornet.
The third phalanx, situated entirely within the hoof, has the same direction as the first and second. It is large and broad, and presents three surfaces separated by well-marked angular borders (see Fig. 96). The anterior surface is oblique downwards and forwards ; it is convex transversely. The inferior surface is. slightly hollowed, and is in relation with the sole, or plantar surface of the hoof.
The superior surface, which is articular, is divided by a median ridge into two lateral cavities, which correspond to the trochlea on the inferior surface of the lower extremity of the second phalanx. The inferior border corresponds in shape with the hoof. The superior border presents in its median part a projection, the pyramidal eminence, which prolongs at this level the anterior surface of the bone. Finally, the posterior border, which is concave, is in contact with a sesamoid bone, the lesser sesamoid, which increases the superior articular surface behind, and is also in contact with the second phalanx.
As we have just seen, the horse possesses but one digit. In the ancestors of the animal—that is, in the prehistoric species which are now extinct (orohippus, miolippus, proto- hippus, or hipbparion)—the number of digits was larger ; this fact conclusively proves that the rudimentary metacarpals of the existing horse are vestiges of digits which have dis- appeared through want of use. In the first of those ancestors —orohippus—there were four digits ; all save the first, the thumb, being then developed. In the others of the series there existed but three digits. It must, however, be noted that in those animals it is always the digit which corresponds to the middle finger of the pentedactyl hand that is longest. In other less ancient species the lateral fingers are reduced to the condition of mere splints of bone. It follows from what has been said that the digit which persists in the equine species should be considered as the third finger, and that the rudimentary metacarpals represent lateral digits considerably atrophied.
70 THE ARTISTIC ANATOMY OF ANIMALS
This disappearance of the lateral digits cannot excite surprise when we consider the functions of the organs. Becoming useless, they must undergo gradual atrophy from want of use. | ' There undoubtedly is, in this former existence of supple- mentary digits in the horse, something analogous to what we still find in the pig ; where the two principal digits are accompanied by two shorter ones, which very probably, from their infrequent use, are destined to disappear in a more or less distant future.
J
Proportions of the Arm, the Forearm, and the Metacarpus
As a supplement to the study of the anterior limbs which we have just finished, it appears necessary to give some indications of the relative proportions of certain of the segments which form these limbs in the plantigrades, the digitigrades, and the ungulates.
First, we would remark that, in following this order of classification, the scapula becomes less and less narrow, © and assumes a form more and more elongated. . In order to convince ourselves of this, it will be sufficient to study the — bone first in man, then in the bear, the cat, dog, ox, and finally in the horse.
As to the proportions of length, which are those we should chiefly study, we shall commence with the comparison of the forearm and arm—that is to say, the radius and the humerus. The radius is found to be longer in proportion to the humerus, as the number of digits is smaller, and the hand loses more and more the functions of an organ of prehension. In man, the radius is shorter than the humerus ; in the horse, on the contrary, it is longer.
To give an idea of this proportion, we shall employ what is known as the antibrachial index. This index gives the relation which exists between the length of the forearm and ‘that of the humerus; the length of this latter, whatever may be the actual measurement, is represented by a fixed
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OSTEOLOGY AND ARTHROLOGY 71
figure, the number 100. A very simple arithmetical opera-
: _ tion gives the proportion—
forearm X I00 humerus
, the quotient obtained furnishes the index.
The index is less than roo if the forearm is shorter than the bone of the arm. The index is more than roo if, on the contrary, the forearm is longer.
In man, the radius is shorter than the humerus; indeed. in adult individuals of the white race the average index is 74.
In the bear, the length of the radius approaches closely to that of the humerus; the index is about go. In the skeleton of a bear in the anatomical museum of the Ecole des Beaux-Arts, the humerus is 33 centimetres in length, and the radius 30 centimetres.
In the cat, the radius is very little shorter than the humerus. In the dog they are equal. The antibrachial index of the latter is, accordingly, roo.
In the horse, the radius is longer than the humerus ; the index is therefore above 100. Thus, in the skeleton of the horse which we have in the museum of the Ecole des Beaux Arts, the index is 113—length of humerus, 29 centimetres ; length of radius, 33 centimetres. In other skeletons which we have measured we found: in one, 108—humerus, 34 centimetres ; radius, 37 centimetres ; in another, r16— humerus, 25 centimetres ; radius, 29 centimetres.
The metacarpal bone undergoes, relatively to the humerus,
a proportional elongation, analogous to that of the forearm.
In man, the length of the metacarpus is contained about 54 times in that of the humerus ; in the bear, it is contained 4 times ; in the dog, 24 times ; in the horse, 14 times only.
It is well known that the proportions vary according to race, and that what we have here given are but the general indications. :
The Articulations of the Anterior Limbs
The knowledge of human arthrology which we presume the reader to have previously acquired makes it unnecessary for us to enter into numerous details regarding the configura-
72, THE ARTISTIC ANATOMY OF ANIMALS
tion of the articular osseous surfaces and the disposition of the fibrous bands that retain them in position. Accordingly, in the description which follows, and also in that of the articu- lations of the posterior limbs, we shall occupy ourselves but very briefly with the details above referred to, so as to devote ourselves especially to the indication of the movements— that is to say, of that which, while easily comprehended on recollection of former studies, presents the greatest interest from the artistic standpoint in these studies in comparative anatomy.
The Scapulo-Humeral Articulation, —The head of the humerus and the glenoid cavity of the scapula being in contact, the two bones are bound together by a rather loose articular capsule, which is strengthened by the muscles of this region which fulfil the function of active ligaments.
This articulation, so movable in every direction in the human species, is not so much so in quadrupeds ; the arm in the latter, as also the shoulder, being kept in contact with the lateral region of the thorax by the numerous muscles which surround it.
eS eS Ul lU eel |S
Of the movements performed by the humerus, flexion and
extension are the most extensive ; those of abduction and adduction are much less so.
It is necessary, before proceeding further, to determine
what the two principal movements which we have just menticned really are, viz., flexion and extension. ' We know that in man the displacements of the humerus which take place in the antero-posterior direction are known as movement or projection forwards, and movement or pro- jection backwards, respectively. We do not say that the humerus is flexed or extended, because, in reality, on account of the position which the skeleton of the shoulder occupies, it is not able to flex or place itself on the line of prolongation of the scapula with which it articulates.
In quadrupeds it is not so. The humerus and the scapula are contained in almost the same vertical plane ; and the bone of the arm can take, in relation to the latter, the positions characteristic of flexion and extension—that is, of approach to the scapula and removal from it.
SS ———
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OSTEOLOGY AND ARTHROLOGY 73
What makes the meanings of these terms a little con- fusing is that, in human anatomy, some authors consider the backward movement of the humerus as extension, and the forward movement as flexion ; in order to be able to compare these movements to those that the femur executes in relation to the pelvis.
Now, in our opinion, the iGioAtiOn of this correspondence is not absolutely necessary ; since it ceases to be exact if we wished, from the point of view of the direction given to other segments of the skeleton, to establish the same relation between the elbow and the articulation of the knee.
It is therefore indispensable, when discussing quadrupeds, to discontinue these terms, in order the more readily to recognise that: in flexion the inferior extremity of the humerus is directed backwards ; in extension, on the con- trary, it is directed forwards. In the first case the humerus approaches the scapula ; in the second, on the contrary, it moves away from it.
These movements, which take place during walking, are executed in the following manner : When one of the anterior limbs is at the end of that stage of progression which is called support (see p. 289, Displacements of the Limbs)—that is to say, during the time that the foot remains in contact with the ground, whilst the trunk is moving forward—the direction of this limb becomes more and more oblique downwards and backwards. At a certain moment the limb is raised from the ground, to be carried forwards, in order to be again
pressed on the ground, and recommence a new resting stage. In these different phases the humerus is flexed. But at
the moment that the limb, when carried forwards, is about to resume its contact with the ground it becomes directed obliquely downwards and forwards; then the humerus is in the position of extension. . |
During these movements of the humerus, there exists an essential factor—that is, the scapular balance. (It is the same as what occurs in man when he balances his arm in the antero-posterior plane.) When the humerus is flexed, the scapula moves in such a way that the superior portion projects forwards ; when it is extended, the scapula, on the
74. THE ARTISTIC ANATOMY OF ANIMALS
other hand, is inclined more backwards.. But it is necessary to add that, during these displacements, the scapulo- humeral angle varies ; it tends to close during the flexion of the humerus, and becomes more open during extension.
The movements and the relations of the humerus and the scapula are clearly represented in Figs. 41 and 42, reproduced from the chromophotographicstudies of Professor Marey—studies relative to the analyses of the movements of the horse.* They show clearly the movements of flexion and extension of thé humerus, also the balancing of the scapula which accompanies the movements.
Fic. 41.—FLEXION OF THE FIG. 42.— EXTENSION OF THE
HuMERUS: RIGHT ANTERIOR Humerus: RicHtT ANTERIOR LIMB OF THE HorRSsE, EXTERNAL LIMB OF THE HORSE, EXTERNAI. SURFACE (AFTER A CHROMO- SURFACE (AFTER A CHROMO- PHOTOGRAPHIC STUDY BY PRo- PHOTOGRAPHIC STUDY BY PRO- FESSOR MAREY). FESSOR MAREY).
The Articulation of the Elbow, or the Humero-ulnar Articulation.—In this articulation, which is constructed in the form of a true hinge, the movements of flexion and ex- tension alone are possible. In flexion, the forearm, directed forwards, is folded on the arm, with which, in certain circum- stances, it comes in contact. For example, in a horse of
* E. J. Marey, ‘ Analyses of the Movements of the Horse by the Chromo- photograph ’* (La Natura, June 11, 1898).
OSTEOLOGY AND ARTHROLOGY | 75
mettle which leaps over an elevated obstacle, the animal forcibly raises his fore-limbs by flexing them. Flexion is produced to the same extent, and even more so, and fora longer period, in felides which crouch.
In extension, on the contrary, the forearm is carried back- ward. This movement being limited only by the contact of the tip of the olecranon with the bottom of the olecranon fossa of the humerus, the forearm is enabled, in this case, to move until it is in line with the arm. For example, during walking, when one of the anterior limbs, having reached the end of its resting stage, is considerably inclined downwards and backwards.
The apex of the olecranon process—that is to say, the point of the elbow—forms a marked prominence, more salient in flexion than in extension, as in the corresponding region of the human elbow.
The Radio-ulnar Articulation.—It is in the dog and the cat, in which the two bones of the forearm articulate by their extremities only, and remain separate in the rest of their extent, that the articulations call for special notice.
In the upper part, the radius rotates on itself; while below, it rotates around the ulna. It follows that the fore- arm, which in all quadrupeds is in a state of permanent pronation, can, in carnivora, take the position of supination, or rather, of demi-supination. In fact, whatever be the mobility of the two bones of the forearm, the movement is not able to bring the palmar surface to the front, but only to direct it towards the median line.
The Articulation of the Wrist.—Here are found, as in man, three superimposed articulations: the radio-carpal, intercarpal, and carpo-metacarpal.
If we remember the movements which take place at the plane of these articulations in man, and take account of the fact that the mobility of the limbs is reduced just in proportion as they are simplified in structure so as to become organs of support only, we can easily comprehend that, in the horse and the ox, and, in a word, animals that have a canon bone, the movements of the wrist are little varied in character, while in carnivore, on the other hand, they are relatively more so.
76 THE ARTISTIC ANATOMY OF ANIMALS
We will remember that in the ox and the horse the region of the wrist is called the knee. .
In flexion, the hand is bent backwards ; in extension it is carried forwards. These two movements take place especially in the radiocarpal and intercarpal articulations. In the first of these articulations, it is the superior row of the carpus which glides backwards and forwards on the corresponding articular surface of the forearm. In the second articulation, it is the second row which moves ; gliding on the inferior articular surfaces of the row above it. This inferior row carries the metacarpus with it; for the carpo-metacarpal articulation is much less mobile than either of the other two.
In flexion, the articular surfaces are separated from one another in front; and the changes of form which result from this are noticeable on the anterior surface of the ‘knee.’ Moreover, at that moment this region contrasts markedly in its outlines with the parts above it and below it—that is to say, with the corresponding. surfaces of the forearm and of the canon bone.
As for the lateral movements, by which the hand is inclined outwards and inwards in its movements at the wrist, they exist to an appreciable extent in the cat and the dog only ; in order to understand this, it is enough to com-
pare the shape of the articular surfaces of this region in ©
carnivora and the horse, for example. In the latter, those surfaces are almost plane; in the cat, on the contrary, they are curved (inferior surface of the forearm, concave ; superior border of the carpus, convex). These latter, then, are, in form, similar to those which exist at the same level in the human being; this explains the possibility of analogous movements of the whole hand—that is to say, of the move- ments of abduction and adduction.
The Metacarpo-phalangeal Articulations.—With regard to the mobility, it is in these articulations, as in those of the wrist—that is to say, although in all quadrupeds the first phalanges can be flexed and extended on the metacarpus, it is only in the cat and dog that lateral movement is possible. Indeed, in the horse, in which the principal metacarpal ter-
| | |
Se ee eee eee "
OSTEOLOGY AND ARTHROLOGY 77
minates inferiorly in two convex surfaces, which are separ- ated by a crest ; and where the whole articulates with a cavity on the superior extremity of the first phalanx ; because of the hinging of these surfaces, there can only be movements of opening and closing of this articulation. The first phalanx is directed backwards during flexion and forwards during extension. In the dog and the cat the digits can be separated from each other, and also drawn together—that is to say, abducted and adducted ; but, as in man, these movements can be made only when the first phalanges are in the state of extension. During flexion they are impossible, because of the tension of the lateral ligaments, which increases as the flexion is more pronounced. This can be demonstrated, for example, in the cat, which, in order to separate the digits, opens the hand widely —that is to say, forcibly raises the first phalanges.
The Interphalangeal Articulations. —The phalanges are in contact with one another by surfaces, which, on one side, are of trochlear form, and, on the other, are moulded on these trochlee ; accordingly, at the level of these articulations, the movements of flexion and extension only can take place. .
In the felidze, the claws which the third phalanges bear cannot be utilized when the latter are in a state of extension, at which time, being forcibly raised, they are, in fact, placed on the outer sides of the phalanges, which are grooved to receive them. But when the animal wishes to use them, it flexes those third phalanges, of which
the terminal extremity is then projected forward, and
the claws are ready to fulfil their function. But at the same time it extends the first phalanges, to produce a certain tension of the flexors of the digits, and thus enable the latter to act with greater efficacy, with a minimum of contraction. We can demonstrate this action experimentally on ourselves. It is enough to carry the first phalanges forcibly into a state of extension; the third phalanges then become flexed, quite spontaneously, by the tension of the tendons of the flexors which are inserted into them.
78 THE ARTISTIC ANATOMY OF ANIMALS
At the same time, if we examine the felide which we have taken as examples, when the first phalanges are in the state of extension, the digits will be found to be separable, as we have already indicated in connection with the metacarpo- phalangeal articulations, with the result that the claws are then able to lacerate a wider surface.
The extension of the ungual phalanx, which determines the retraction of the claw and stops its action, is the mechanical result of an elastic, fibrous apparatus which is attached to each of the third phalanges, and has its origin of the second.
THE POSTERIOR LIMBS*
The posterior limbs are divided, as are the inferior limbs of the human being, of which they are the homologues, into four parts: pelvis, thigh, leg, and foot.
The Pelvis
The pelvis, which incompletely limits the abdominal cavity, inferiorly in the vertical position of the body and posteriorly in the normal attitude of quadrupeds, is formed by the iliac bones and sacrum—the ceccyx forming a pro- longation of the latter. We have already described the two latter (pp. Io and II) in connection with the vertebral column, of which they form the inferior or posterior por- tion or segment, according to the attitude of the individual.
The Iliac Bone.— The iliac or coxal bone, is a paired or non- symmetrical bone, united below to its fellow of the opposite side, while it is separated from it above by the sacrum.
In all animals, as well as in man, the iliac bone, at the beginning of life, consists of three parts, which afterwards unite and fuse together and join at the middle of the bottom of a deep cavity which is situated on the outer aspect of the bone—the cotyloid cavity.
Of those three portions when examined in the human iliac bone, that above the cavity is the ilium; that on the inside is the pubis ; and the last, the lower one, is the ischium. In
* Examine Figs. 21, 33, 34, 38, 39, 49.
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OSTEOLOGY AND ARTHROLOGY 79
quadrupeds, the iliac bone being, in its entirety, directed much more obliquely downwards and backwards, the relative position of these constituent parts is a little modified: the ilium is in front, the pubis is still internal, but in a more inferior position, and the ischium is behind the cotyloid cavity. We notice this peculiarity of the development of the iliac bone because it is customary to continue to apply to
6 8 |
Fic. 43.—THE Lerr Iriac Fic. 44.—Lerr ILtiac BONE OF A BoNE OF THE HUMAN QUADRUPED (HorsE): EXTERNAL BEING: EXTERNAL SuwUR- SURFACE.
FACE, PLACED IN THE Posi!- TION WHICH IT WOULD OCCUPY IN THE SKELETON OF A QUADRUPED.
1, Cotyloid cavity; 2, ilium, external iliac fossa (directed upward in the horse); 3, iliac crest; 4, anterior iliac spine (directed inwards in the horse, it is the
1, Cotyloid cavity; 2,ilium; angle of the haunch); 5, posterior iliac 3, iliac crest ; 4, anterior iliac spine (directed inwards in the horse ; it crest; 5, posterior iliac spine; is the angle of the haunch); 6, pubis; 6, P: 7, tuberosity of the 7, tuberosity of the ischium; 8, obtu- ischium; 8, obturator fora- rator foramen; 9, ischiadic spine, or men; 9, ischiadic spine. subcotyloid foramen.
the osseous regions which correspond to these parts the names by which they were known when independent bones.
The bones which form the skeleton of the pelvis of quad- rupeds are proportionally more elongated and less massive than those of the human pelvis (Figs. 43 and 44).
We find, on the external surface of the iliac bone, the cotyloid cavity, whose border is interrupted by the cotyloid notch ; a deep notch which looks downwards.
ie AM
80 THE ARTISTIC ANATOMY OF ANIMALS ’
In front of this cavity is the ilium. This portion, narrow
in the part which is next the cavity, is directed forwards and .
upwards, expanding more and more as it passes upwards. It presents an external or superior surface (external in some animals, superior in others), which recalls the external iliac fossa ; and an internal cr inferior surface, at the superior part of which is found the auricular surface for articulation with the sacrum.
The anterior border of the ilium is rough ; this is the iliac crest, at the extremities of which we find, below or outside, a prominence which corresponds to the anterior superior iliac spine of man ; and internally another projection which corresponds to the posterior iliac spine.
Immediately above the cotyloid cavity is a rough crest, which is known as the supracotyloid crest, which is, how- ever, no other than the homologue of the sciatic spine. In front of this prominence, the border of the ilium, which is notched, forms the great sciatic notch.
If, still taking the cotyloid cavity as the point of
departure, we proceed inwards—that is, towards the median ~
line of the body—we find the pubis; if in a posterior
direction, the ischitum. These two portions, pubis and —
ischium, limit an oval orifice, the subpubic foramen. In the human skeleton, the pubis of one side is united to that of the opposite side, to form the pubic symphysis.
In the animals which we are now studying a portion of the —
ischium enters into the formation of the symphysis ; in other words, it is formed, not only by the body of the pubis, but also by the descending branch or ramus of the pubis and a portion of the ascending branch or ramus of the ischium, which are fused with those of the opposite side. It results that, though in the human being the symphysis is short and the ischio-pubic arch large, in quadrupeds it
is the opposite. In them the arch is a mere slot, and being _
formed by the ischium alone, merits the name of the ischial arch. The ischio-pubic symphysis is very large, and forms a horizontal surface relatively extensive, a sort of floor, on which rest certain organs which occupy the cavity of the pelvis.
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OSTEOLOGY AND ARTHROLOGY 81
The posterior and external angle of the ischium is rough and prominent ; it is the tuberosity of the ischium. This forms a projection under the skin ; it also does in man when the trunk is strongly inclined forwards, while the thighs are maintained in the vertical position. In marsupials—opos- sum, kangaroo, and phalanger—the pelvis at its pubic region is surmounted by two bones, situated one on each side of the median line, and arranged in the form of a fork of two prongs (Fig. 45). These, which are called marsupial bones, support the pouch which, in animals of this genus, lodges
3 3 2 , EAC. Fic. 45.—Pusic REGION OF THE PELVIS OF A MARSUPIAL (PHALANGER, Fox).
1, Symphysis pubis ; 2, obturator foramen ; 3, marsupial bones.
their young, which, at the time of birth, are incapable of supporting a separate existence, their development being absolutely incomplete.
In the cetaceans—for example, the dolphin—because of the absence of posterior limbs, the pelvis is represented by two separate bones only, which have no connection with the vertebral column. In birds, the pelvis is remarkable for its elongated form (see for its form Fig. 21, and for details Fig. 46). The cotyloid cavity is pierced by an Opening, and presents on its posterior border, which is
6
82 THE ARTISTIC ANATOMY OF ANIMALS
here a little prominent, a surface with which the sree ‘trochanter i is in contact.
The ilium is very highly developed, and is fused in chia median line with the ilium of the opposite side, the last dorsal ‘vertébre, the lumbar vertebre, and the sacrum. Because of these relations with the dorsal vertebra, it is in contact | anteriorly with the last ribs, which consequently meray from each side of the iliac region of the pelvis. :
The ischium forms a plate’ of bone which, in part, closes the external portion of the cavity of the pelvis. Its superior
Fic. 46.—PELVIS OF A BIRD (THE COCK): EXTERNAL SURFACE, LEFT SIDE.
1, Ilium; 2, ischium; 3, pubis; 4, inferior extremity of the pubis ;_ 5, sciatic foramen; 6, oval foramen, homologous to the obturator; 7, coccygeal vertebrae.
border is separate for a certain distance from the external border of the ilium ; there is thus left an opening of more or less considerable size, which represents or takes the place of the great sciatic notch. |
The pubis, long and slender, is in connection with the inferior border of the ischium, of which it follows the general direction ; and circumscribes with this latter, below the cotyloid cavity, an oval orifice, which is the homologue of the obturator foramen. Its inferior extremity reaches beyond the corresponding part of the ischium, bending
OSTEOLOGY AND ARTHROLOGY 83
, towards the middle line, but without joining the pubis of
_ the opposite side. On this account there is no symphysis pubis in birds. Nevertheless, an exception must be noted in the case of the ostrich, the pubic bones of which meet in the middle line, and are articulated in form of a symphysis.
The Thigh
A single bone, the femur, forms the skeleton of this portion of the lower limb.
The Femur.—tThe bone of the thigh is, in man, directed downwards and inwards; this obliquity, we may remind the reader, is due to the difference in length of the two condyles which form its inferior extremity ; the internal is the more prominent, the result of which is that when the femur is held vertically, the internal condyle descends lower than the external. Now, as those two articular
expansions rest on the horizontal plane formed by the upper extremity of the tibia, it follows that the superior part of the femur inclines towards the side of the shorter con- dyle—that is to say, outwards—and that, the leg being vertical, it and the bone of the thigh unite in forming an angle, of which the apex is directed towards the inner side of the knee.
In many mammals the two condyles are equally pro- minent, the result of which is that the femur inclines neither inwards nor outwards, but is contained in a plane parallel to the axis of the trunk; while the leg is included in the same plane. Nevertheless, although contained in the plane which we have just indicated, the femur is obliquely placed, and directed downwards and forwards ; it accord- ingly forms, with the pelvis, an angle, of which the opening is directed to the anterior aspect of the body.
In reptiles and in birds the femur and leg are both placed in the same plane, but this plane is not parallel to the axis of the trunk. This is the result, on the one hand, of the thorax being wide, and, on the other hand, of the femur,
_ which is directed forwards, being in contact by its anterior extremity with the lateral aspect of the costal region, it is. 6—2
84 THE ARTISTIC ANATOMY OF ANIMALS
thus necessarily placed in a direction forwards and outwards, and the knee is further removed from the axis of the trunk than is the articulation which unites the thigh with the pelvis,
b-
i 4
}
The femur, like the humerus, is almost completely en-—
veloped by muscular masses, which bind it to the laterai —
walls of the abdomen. Its inferior extremity alone is free, ~
and is always the more so in proportion to its elongation—
: L.
that is to say, as it belongs to an animal whose foot is more divided. The femur in this respect conforms to the law —
which we have indicated in connection with the bone of the
;
arm, in which the development, as to length, is in propor-—
tion to the division of the hand.
If we compare the femur of certain animals with that —
of man, we see that the corresponding details of form are readily recognisable, but they are slightly modified.
Thus, on examining the superior extremity, we find there ~
a head, a neck, a great trochanter, and a lesser; but the ©
neck is usually short and thick, and the great trochanter
does not occupy the same level with regard to the articular —
head of the bone. In man, the great trochanter does not rise to the level of the head of the femur ; in the dog and
the cat it approaches that level; in the horse and in
ruminants it rises above it.
With regard to the inferior extremity, its surfaces ~
undergo modifications which are further accentuated as we pass from the digitigrades to the ungulates, or un- guligrades. We know that in man the femoral trochlea is continuous behind, without interruption, with the con- dyles—that is to say, that each of the condyles is the con- tinuation of one of the lips of the trochlea. We have just said that the trochlea is continuous without interruption with the condyles; this is ‘accurate.. Nevertheless, we must remark that, at the level of the junction of these surfaces, the bone presents a slight constriction, which is more marked on the external than on the internal aspect. This constriction, which is but slightly marked in man, is
accentuated in the dog and the cat ; in the ruminants and —
the solipeds it is still more pronounced so that we may
OSTEOLOGY AND ARTHROLOGY 85
say that in these latter the trochlea and the condyles are almost completely separated.
There is another modification in regard to the”promi- nence and extent of the two lips of the trochlea. In man, the external lip of the trochlea reaches higher than the internal, and it is more prominent in front. In the dog, these lips are equal with regard to thickness, but the external still reaches higher than the internal; in the cat, they are equal in every respect; in ruminants and solipeds the internal lip is wider, thicker, and rises higher than the external.
In animals the trochlea is, as a general rule, narrower than in man, and the condyles are more prominent pos- teriorly ; so that, when viewed from one of the lateral aspects, the inferior extremity of the femur is, in them, better developed in the antero-posterior direction.
In birds, the femur is shorter than the bones of the leg ; its great trochanter is in contact with a prominence which occupies the posterior part of the border of the cotyloid cavity. Instead of articulating at the level of the knee, with the knee-cap and tibia only, as in man, it articulates, in addition, with the superior extremity of the fibula. A similar arrangement is found in marsupials and reptiles.
The Knee-cap.—tThis bone, developed in the thickness of the tendon of the triceps muscle of the thigh, is in contact, by its posterior surface, with the femoral trochlea. The two articular surfaces which are applied to the lips of the trochlea present, with regard to their extent, an inequality which is in proportion to the arrangement which we have above indicated—that is, while in man it is the external surface which is the larger, in the horse it is the internal. We shall see what the general form of the knee-cap is when we come, later on, to study more particularly the posterior limbs of some animals.
The Leg
The skeleton of the leg consists of two bones: the tibia and the fibula. The tibia is the more internal and the
86 THE ARTISTIC ANATOMY OF ANIMALS
larger of the two ; the fibula is slender, and situated on the
outer side, and a little posterior to, the preceding. The
fibula is more or less developed according to the species ; in some it is complete, in others it is very much atrophied.
This peculiarity may be compared with that which we have drawn attention to regarding the development of the ulna ; but here the seriation is less distinct. Not only in the different species, but even in the individuals of the same species, the development of the fibula presents little regu- larity. In quadrupeds, the bones of the leg are directed obliquely downwards and backwards, so that they form, with the femur, which is directed obliquely downwards and forwards, an angle, the apex of which is placed at the anterior surface of the knee.
Tibia.—The tibia of quadrupeds is readily comparable
with that of man; as in the case of the latter, its shaft has
three surfaces —an external, which is hollowed out in its ©
upper portion, and becomes anterior below; an internal,
slightly convex and subcutaneous; the posterior, which
presents, in its superior part, a crest, the oblique line of the tibia, and some rugosities. The borders separate the —
surfaces. The anterior border, or crest of the tibia, is
prominent in its superior part; below it gradually dis- ’
appears in passing towards the internal aspect of the inferior extremity. The external and internal borders separate the corresponding surfaces from the posterior one.
The superior extremity is thick, and expands in forming three tuberosities: two lateral and an anterior. The anterior tuberosity, situated at the superior part of the crest of the tibia, is very prominent ; for this reason the superior extremity is very much expanded in the antero- posterior direction—hence it results that this diameter is equal to the transverse, and sometimes even greater. In man, it is the latter which is the larger. The anterior tuberosity is visible under the skin.
The inferior extremity, less thick, is prolonged internally by a prominence which corresponds to the internal mal- leolus of man. In animals whose fibula is but slightly developed the tibia presents, on the external part of its
i
OSTEOLOGY AND ARTHROLOGY 87
inferior extremity, a small prominence, which replaces the
fibular malleolus. The ruminants must, however, be ex-
cepted, in which we find in this region a special bone, which certain authors look on as the inferior part of the fibula
(see p. 97). The inferior surface of this extremity of the
tibia is articular ; and is in contact with one of the tarsal bones, the astragalus. Because the superior surface of this latter has the form of a pulley, a pulley much more marked than that on the human astragalus, the correspond- ing surface of the tibia, which has the opposite form, presents two lateral cavities, separated by a median ridge, which is directed forwards and slightly outwards; this ridge projects into the groove of the pulley.
The Fibula.—This bone, situated at the back of the external surface of the tibia, is, as we have said, more or less developed. Its superior extremity, or head, articu- lates with the external tuberosity of the tibia. Its inferior extremity, when it exists—it is this which disappears in animals which have the fibula incompletely developed— forms a prominence which, placed on the external surface of the inferior extremity of the tibia, articulates with the astragalus, and recalls the external malleolus of man.
We have stated above that it is the inferior extremity of the fibula which disappears when the bone is incom- pletely developed; it is necessary to except the bat, in which the fibula, fairly well developed at its inferior extremity, by which it articulates with the tibia, thins off in its superior portion, and does not reach the corre- sponding extremity of the latter. Further, as in this animal the surface of the knee, which corresponds to the anterior surface of the same region in other animals, is turned backwards, the result is that the fibula is situated on the inner side of the tibia, instead of being placed on the outer.
The Foot
The foot, in animals, as well as in man, is formed of three portions, which, as we pass from the part which articulates with the leg towards the terminal extremity, are: the tarsus,
88 THE ARTISTIC ANATOMY OF ANIMALS
the metatarsus, and the toes. These three portions are the
homologues of the carpus, the metacarpus, and the fingers, —
which, as we have already seen in the case of the hand, are the osseous groups which form its skeleton. The tarsus is formed of short bones, as the carpus is; these are, in man, seven in number. The bones are arranged in two rows: one, the posterior, formed of two bones superimposed— the astragalus, by which the tarsus articulates with the leg, and the calcaneum, which forms the prominence of the heel ; and an anterior row formed of five juxtaposed ones—the cuboid, situated externally, and the scaphoid internally, in front of which are found the three cuneiforms. To the tarsus succeeds the metatarsus, whose form reminds us very much of that of the metacarpals.
With regard to the toes, which we enumerate in proceeding from the most internal to the most external, they are formed of phalanges, which are three in number for the four outer toes ; but the number is reduced to two in the case of the first—that is, the so-called great-toe. :
The bones of the tarsus are not seven in all animals ; they
are fewer in ruminants and solipeds. We already know —
that, in the latter, the metacarpals and the digits are equally reduced in number ; the same is the case for the metatarsals and the toes. We will analyze these differences when dealing with the species individually.
When we studied the anterior limbs, we saw in passing from the plantigrades to the digitigrades, and finally the uugulates, or unguligrades, as the hand became hyperex- tended, the carpus was raised and: more and more re- moved from the ground. We shall establish the existence of the same condition in the posterior limbs; in the plantigrades the tarsus rests on the ground; in the digiti- grades it is removed from it ; while in the unguligrades the distance which separates it from the point of support is still more considerable; and it is, indeed, necessary to imagine that if these latter were plantigrades, would occupy the position on the ground which is indicated by
Fig. 47. In veterinary anatomy the tarsus is called the ham; a
od
ee ae ee ee eee.
Seal
OSTEOLOGY AND ARTHROLOGY 89
name we adopt in conformity with usage, but which we cannot but regret, as in human anatomy the ham is the region of the posterior surface of the knee.
The general arrangement of the region of the digits of the posterior limbs in birds, presents some points of interest.
We shall merely say with regard to the metatarsus, that it is formed by a single bone, which in the cock is furnished towards its inferior third with a pointed process, the spur. At the inferior part, there is, however, found another, which is but very slightly developed, and with which the first phalanx of the innermost toe articulates.
The toes are, in the majority of species, four in number :*
EA.C,
Fic. 47.—-PoSTERIOR LIMB OF THE HORSE PLACED IN THE POSITION WHICH IT SHOULD OCCUPY IF THE ANIMAL WERE A PLANTIGRADE : LEFT LIMB, EXTERNAL SURFACE.
I, Tibia; 2, astragalus; 3, calcaneum ; 4, metatarsus; 5, first phalanx ; 6, second phalanx ; 7, third phalanx.
an internal, which is directed backwards, and corresponds to the great-toe; the others are directed forwards. This arrangement is constant in grallatores (wading birds), galli- nacez + (domestic fowls), and raptores (birds of prey).
In climbing birds (parrots, woodpeckers, and toucans), the
* In spite of the fact that the custom is to designate the terminal por- tions of the foot of birds by the name of digits, we prefer to employ here the terms foot and toes. In adopting this decision we believe we are acting according to a more didactic method. Homology of names should, in our opinion, always accompany homology of regions.
+ With regard to the gallinacee, we must add that in certain varieties the number of toes is five; those which are directed forwards are three in number ; the internal one which passes backward, is double. The two toes which are the subject of this special arrangement are placed very close together, and are nearly always superimposed. This condition is found in the Houdan and Dorking breeds.
go THE ARTISTIC ANATOMY OF ANIMALS
innermost toe is not only directed backward, but the external — toe accompanies it in that direction ; consequently, there are — two posterior and two anterior toes. Sometimes they are all directed forwards; this disposition is found in the martins. In some birds, the number of toes is reduced to . three : the cassowary shows this reduction ; in others, the number is still further diminished—the ostrich, for example, has but two.
Further, we find that, in general, the number of the phalanges increases, when we examine the toes in com-
€a.C.
Fic. 48.—-SKELETON OF THE Foot OF A BIRD (THE Cock): Lert SIDE, EXTERNAL SURFACE.
1, Metatarsus; 2, spur, 3, rudimentary metatarsal; 4, first toe; 5, second toe ; 6, third toe; 7, fourth toe.
mencing with the most internal (Fig. 48): this has two ; then the following one three; that which comes next in: order has four; and the most external toe has five. The phalanges of this last are short; so that, although it is formed by a larger number of bones, it is not the longest of the toes.
THE POSTERIOR LIMBS IN SOME ANIMALS. _
Plantigrades: Bear (Fig. 33, p. 50).—The external © iliac fossa is very deep. The femur is longer than the ~ bones of the leg; the great trochanter does not reach the ©
OSTEOLOGY AND ARTHROLOGY gI
level of the head of the femur. The fibula is well developed ; it is united to the tibia at its superior and inferior extremities only.
The foot, which, as in the case of the hand, rests on the ground by the whole extent of its plantar surface, presents five toes ; the shortest of these is the internal—that is, the toe which corresponds to the great-toe in man; the third and fourth are the longest, and they are almost equal ; there is a very slight difference in favour of the fourth, which is slightly superior in dimensions to the third. _
Digitigrades: Cat, Dog (Fig. 34, p. 52).—The ex- ternal iliac fossa, which looks outwards, is deep ; the iliac
le
OOK,
EX.C.
Fic. 49.—PELVIS OF THE Doc, SEEN FROM ABOVE.
1, Iliac crest; 2, external iliac fossa , 3, sacrum; AA’, bi-iliac diameter ; BB’, bi-ischial diameter.
crest is convex anteriorly, the convexity is continued from one iliac spine to the other.
In the dog, the distance which separates the anterior iliac spines is less than that which separates the ischia (Fig. 49). On a skeleton which we measured, the transverse diameter, the distance from the anterior iliac spine of one side to that of the opposite side, was 8 centimetres, whilst the distance which separated the ischia was 105 millimetres ; on another skeleton, the first measurement was 127 metres, and the second was 146 millimetres. It seems to us unneces- sary to multiply examples.
In the cat, the iliac spines are but slightly marked ; the
92 THE ARTISTIC ANATOMY OF ANIMALS
result is that the iliac crest is almost confounded with the inferior and superior borders of the ilium. The two dia- meters referred to above are almost equal (Fig. 50).
We draw particular attention to what we have just noted in regard to the