tu Memory of 


5 m ammalogist > ite 
Luv’ Paleontologist“B 


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some 


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AN INTRODUCTION 


TO THE 


Do LE OLOGY ie Tie WM A MMA Lee. 


COT [A OE 


Remington Kellogg 


AN TN ERODUC TION 


TO THE 


OSTEOLOGY OF THE MAMMALIA: 


BEING THE SUBSTANCE OF 
THE COURSE OF LECTURES DELIVERED 
AT 
THE ROYAL COLLEGE OF SURGEONS OF ENGLAND 
IN 1870. 


BY 


WILLIAM HENRY FLOWER, F.RS., FRCS, 


HUNTERIAN PROFESSOR OF COMPARATIVE ANATOMY AND PHYSIOLOGY, 
,/ AND 
CONSERVATOR OF THE MUSEUM OF THE COLLEGE. 


WITH NUMEROUS ILLUSTRATIONS. 


SECOND EDITION, REVISED. 
REMINGTON KELLOGG 
LIBRARY OF 


MARINE MAMMALOGY 

SMITHSONIAN INSTITUTION 
London : 

MACMILLAN, AND CO. 
1876. 


[Zhe Right of Translation and Reproduction ts Reserved. | 


LONDON : 
R. CLAY, SONS, AND TAYLOR, | 


REREAD STREBT HILL, QUEEN VICTORIA STREET. 


Pie i ea Cs, 


THE desire to acquire a knowledge of the structure of some 
portion at least of the Animal Kingdom, now becoming so 
general, is often checked by the difficulty of determining 
where to make a beginning amid the vast extent and 
variety of the materials at hand. 

I have selected for my first course of lectures on Com- 
parative Anatomy at the Royal College of Surgeons, the 
structure and modifications of the Skeleton, because, as 
the framework around which the rest of the body is built 
up, It gives, more than any other system, an outline of the 
general organization of the whole animal, and also because 
it is the most convenient for study, on account of the 
facility with which it can be preserved and examined. 

Moreover, Osteology has special importance in com- 
parison with the study of any other system, inasmuch as 
large numbers of animals, all in fact of those not at 
present existing on the earth, can be known to us by 
little else than the form of their bones. 

In endeavouring to gain anatomical knowledge, it sig- 
nifies little with which group of animals a commencement 
is made. 


vi PREFACE. 


The structure of Man has undoubtedly a more universal 
interest than that of any other organized being, and 
has, therefore, been more thoroughly worked out ; and as 
the majority of terms used in describing the parts com- 
posing the bodies of Vertebrate animals were originally 
bestowed on account of their form, relation, or real or 
fancied resemblance to some object, as they were met 
with in Man, there are advantages in commencing with 
members of the highest class, and mastering their essential 
characters before proceeding to acquire knowledge of the 
other groups. 

But as human anatomy may be taken as a point of de- 
parture from which to set out in the study of that of other 
Vertebrates, so, on the other hand, those whose special 
duty it is to become familiar with its details, will find 
themselves greatly assisted by some knowledge of the 
structure of lower forms. ‘Thus the essential characters 
of the human skull will be much better understood if the 
student will also make himself acquainted with those of 
some simpler condition of Mammalian cranium, as that of 
the dog or sheep. 

Although the present work contains the substance of a 
course of lectures, the form has been changed, so as the 
better to adapt it as a handbook for students. Theoretical 
views have been almost entirely excluded ; and while it is 
impossible in a scientific treatise to avoid the employment 
of technical terms, it has been my endeavour to use no 
more than are absolutely necessary, and to exercise due 
care in selecting only those that seem most appropriate, or 
which have received the sanction of general adoption. 


EREPACL, vil 


With very few exceptions, all the illustrations have been 
drawn expressly for this work, with great care and fidelity, 
by Mr. R. W. Sherwin, from specimens in the Museum of 
the Royal College of Surgeons. 


September 24th, 1870. . 


NOTE TO SECOND EDITION. 


This edition has been revised throughout, and a new 
diagram of the arrangement of the principal bones of the 
skull introduced in place of the table at p. 104 of the 
former edition. 

I have to thank many friends for pointing out errors 
and omissions, most of which, it is hoped, have now been 
corrected. 


May 22nd, 1876. 


CON TENTS: 


CHAPTER Tf. 


PAGE 
CLASSIFICATION -OF THE MAMMATIA +902 6 © (60 oe woe I 
CHAPTER: II. 
RTRASICEE ED TOM 95-9) ci) apy alae aula a BaSwilpritn laos 7 
CHAPTER. III. 
WHE EIR ERRAT: COLUMN... yo. | 5) tee SN le koe Ch eed wie Mos ite) 
CHAPTER: LV. 
SPECIAL CHARACTERS OF THE CERVICAL VERTEBR& IN THE 
HUANENUA IGE A eae ete om em oa Ce ee ie ee ae ae 26 
CHAPTER °V: 
SPECIAL CHARACTERS OF THE THORACIC AND LUMBAR VER- 
GURERCUEN: © PATE MIU Y er tay PARh era gee Cie MU ROIS TTS Uptinss ol Og 


CHAPTER VI. 


SPECIAL CHARACTERS OF THE SACRAL AND CAUDAL VER- 
TEBRA ee eS Rs ht te ee aes Sed Cee 60 


b 


x CONTENTS. 


CHAPTER. VIL. 


THE STERNUM Bene gh tw alae eerie ate oe wet 


CHAPTER: VITL. 


THE RIBS 


CHAPTER IX. 


Pes ouiw gon LE WOG c.f segs (oo. ) s. epot es Veikene wocuine 


CHAPTER.2; 


THE SKULL IN THE ORDERS PRIMATES, CARNIVORA, INSECTI- 
VORA, CHIROPTERA, AND RODENTIA 


CHAPTER XI: 


THE SKULL IN THE UNGULATA, HYRACOIDEA, AND PRO- 
BOSCIDIA 


CHAPTER. 2k 


THE SKULL IN THE CETACEA AND THE SIRENIA . . 


CHAPTER XIiT.. 
THE SKULL IN THE EDENTATA, MARSUPIALIA, AND MONO- 
PREMATA ..° 3 


CHAPTER XIV; 


THE SHOULDER GIRDLE 


. . . . - » . . ® LJ 


PAGE 


72 


87 


96 


128 


185 


265 


221 


CONTENTS. x1 


CHAPTER: XV, 


PAGE 
THE ARM AND FORE-ARM. ... . . mse Ws, Peco ee ee 
CHAPTER, avi: 
TE ETANE). Ol, MANUS 4 (ff ui Oma) WPL a eee ei he oe ee 
CHAPTER’ S Vib 
THE PELVIC GIRDLE 283 
CHAPTER XVIII. 
RE Tie ANDATEG a.) oe oe ace yr ce ee te ne se | ene 
CHAPTER. XTX. 
Meme: EGE ROOT. OR BES) fox, <..+ «ck fol = es Pe- sow Ve OgOG 
CHAPTER XX. 
THE CORRESPONDENCE BETWEEN THE BONES OF THE ANTE- 
RIOR AND POSTERIOR EXTREMITY AND THE MODIFICA- 
TIONS OF THE POSITIONS OF THE LIMBS . . . . . . 328 


TE yey A eke LOS Piet Lite hee ei Ral 


10 


AN INTRODUCTION 
TO THE 


OSTEOLOGY OF THE MAMMALIA. 


CHAPTER I. 
CLASSIFICATION OF THE MAMMALIA. 


Ir is not the object of the present work to enter in 
detail into the subject of the Classification of the Mam- 
malia; but, as it will be necessary to refer frequently to the 
principal subdivisions in which the various animals treated 
of are arranged, a brief outline of the system adopted will be 
necessary. 

A perfect arrangement ot any group of animals can only 
be attained simultaneously with a perfect knowledge of their 
structure and life history. We are still so far from this 
that any classification now advanced must be regarded as 
provisional, and merely representing our present state of 
knowledge. Moreover, as naturalists will estimate differ- 
ently the importance to be attached to different structural 
modifications as‘indicative of affinity, it must be long before 
there will be any general agreement upon this subject. 

B 


2 CLASSIFICATION OF THE MAMMALIA.  [cHApP. 


The classification and the names of the subdivisions 
used throughout this work correspond, in the main, with 
those given by Professor Huxley in his ‘Introduction to 
the Classification of Animals,” 1869. 

The whole of the animals composing the class are arranged 
primarily in three natural divisions, which, presenting very 
marked differentiating characters, and having no existing 
intermediate or transitional forms, may be considered as 
sub-classes of equivalent value, taxonomically speaking, though 
very different in the numbers and importance of the animals 
composing them. 

These three groups, to adopt the names originally pro- 
posed for them by De Blainville, are :—1. MONODELPHIA ; 
2. DIDELPHIA; and 3. ORNITHODELPHIA. 


I. The Monodelphia, sometimes called lacentalia, 
comprise the great bulk of the class. The main characteristic 
of the animals composing it is, that their young are nourished 
for a considerable period within the uterus of the mother 
by means of an organ called the A/acenta, a villous and 
vascular development from the outer surface of the foetal 
envelopes, which, being in contact with corresponding 
vascular developments from the inner wall of the uterus, 
permits an interchange of materials between the circu- 
lating fluids of mother and young, thus brought into the 
closest proximity. This organ varies much in shape and 
structure in the different minor divisions of the sub- 
class. 

It is very difficult to subdivide the Monodelphia into any 
groups larger than orders, or to arrange these orders in 
anything like a linear series, as most of them have affinities 
in many directions. . 

One group may be placed apart as having no distinct 


I. MONODELPHTA. S 


relationship with any of the others, being chiefly distinguished 
by negative characters. This is the order EDENTATA, com- 
prising the Sloths, the Armadillos and Ant-eaters of America, 
and the Pangolins and Orycteropus or Cape Ant-eater, of the 
Old World. These are animals of generally low organiza- 
tion for the division to which they belong. 

The remaining Monodelphian Mammals are :—1. 
PRIMATES, the highest order, culminating in the genus 
Flomo of Linnzus, and compnising also all the animals 
commonly known as Monkeys. With these are generally 
united a group of very inferior structure (Zemurina), con- 
taining the various species of Lemurs and allied animals, 
which, without question, connect the Primates on the one 
hand with the Insectivora, Carnivora, and Chiroptera on 
the other ; though it is doubtful, at present, whether they 
should be associated with the Monkeys, or should con- 
stitute a distinct order by themselves.. 2. CHIROPTERA, or 
Bats. 3. INSECTIVORA, or Hedgehogs, Shrews, Moles, &c. 
4. CARNIVORA, divided. into the Terrestrial Carnivora, or 
Fissipedia, Cats, Dogs, and Bears, and the various modifi- 
cations of these types; and the Aquatic Carnivora, or 
Pinnipedia, Seals, Walrus, and Eared Seals, or Sea Lions. 
5. CETACEA, containing two sub-orders, the M/ystacoceti, 
or Whalebone Whales, and the Odonteceti, Cachalots, 
Narwhals, Dolphins, and Porpoises. 6. SIRENIA, a small 
order of aquatic vegetable-feeding animals, of which the 
Manati (A/anatus) and Dugong (/alcore) are the sole 
living representatives. _ 7. UNGULATA, the very large order 
of hoofed quadrupeds, divided into the Perzssedactyla, or 
“odd-toed” Ungulates, containing the Horse, Tapir, and 
Rhinoceros; and the Artiodactyla, or “ even-toed,” again 
subdivided into four sections. a. The non-ruminating, or 
Suina, consisting of the Pigs, Peccaris, and Hippopotamus. 

B 2 


4 CLASSIFICATION OF THE MAMMALIA. [CHAP. 


b. The cushion-footed, or Zyopoda, the Camels and Llamas. 
c. The Zragulina, or Chevrotains, a group of little deer-like 
animals formerly associated with the Musk-deer. @. The 
Pecora, or true Ruminants, comprising the Deer, Giraffes, 
Antelopes, Sheep, Goats, and Oxen. The last three divisions © 
constitute the order ARuwminantia of Cuvier. 8. Hyra- 
COIDEA, an order consisting of a single genus, Wyrax,a small 
animal having many affinities with the Perissodactyle Un- 
gulata, with which it is often associated. 9. PROBOSCIDEA, 
represented at present only by the two species of Elephant ; 
and 1o. RODENTIA, a well-marked group, but with varied 
affinities, both to the Insectivora and Primates on the one 
hand, and to the Ungulata and Proboscidea on the other, and 
also to the Didelphia. This order contains the Hares, Rats, 
Guinea-pigs, Porcupines, Beavers, Squirrels, &c. 


Il. The sub-class Didelphia contains only one order, 
MARSUPIALIA, consisting of animals presenting great diver- 
sity of superficial appearance and habits of life, although 
all united by many essential anatomical and physiological 
characters. The young are born in an exceedingly rudt- 
mentary condition before the formation of a placenta, and 
are transferred to the nipple of the mother, to which they 
remain firmly attached for a considerable time, nourished 
by the milk injected into the mouth by compression of the 
muscle covering the mammary gland. The nipples are 
nearly always concealed in a fold of the abdominal integu- 
ment, or “pouch” (marsupiun), which serves to support 
and protect the young in their early helpless condition. 
The existing species are entirely confined to Australia, its 
neighbouring islands, and the American continent ; though, 
in former times, they had a more extensive geographical 
range. The Wombats, Kangaroos, Phalangers, Koalas, 


4 


. 


| ORNITHODELPATA. 5 


Bandicoots, Dasyures, Thylacines, and Opossums, are the 
best known representatives of this group. 


III. The Ornithodelphia, equivalent to the order 
MoNOTREMATA, consist of only two existing genera; and 
hitherto, no extinct animals which can be referred to other 
genera of this remarkable and well-characterized group have 
been discovered. These two isolated forms, in many re- 
spects widely dissimilar, yet having numerous common 
characters which unite them together and distinguish them 
from the rest of the Mammalia, are the Orazthorhynchits 
and the Zchédna, both restricted in their geographical range 
to the Australian continent and the island of Tasmania. 
Many of the characters in which they differ from the two 
other sub-classes tend to connect them with the inferior 
group of Vertebrates, the SAuROPSIDA, especially the Lacer- 
tians; for though the name Ovrzithodelphia owes its origin 
to the resemblance of the structure of the female repro- 
ductive organs to those of birds, there is nothing specially 
bird-like about them ; all the Sauropsida (Birds and Reptiles) 
agreeing in these respects. 


The accompanying diagram (page 6) is intended to ex- 
hibit the relationships which appear to exist between the 
different groups of the Mammalia. If all known extinct 
forms were inserted, many of the intervals between the 
boundary lines of the groups would be filled up ; other- 
wise no great modification would be required in their 
relative position. But our knowledge of the systematic 
position and relations of the past forms of Mammalian life 
is in general so imperfect and fragmentary, that it seemed 
better to confine the diagram to a representation of the 
present condition of Mammalian life upon the earth. 


ou PS 


| ian VACIOOV FAM 


a 


VIHd'TACONOW VIHdTACOHUNIO| 
( ven i pivanzo VL VIVZULONON) 
Tr ize eke ee 
ee 


Pee ee ei 
VLVINONA (1d/aS0mowd 
VL Pate es ) TAL IVOOSSIAAL 


tee e = (vrwaao ay 


e 


, 


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V DOVE oL, Cate = VICAAILISSEAL ag Se \FITVIdOASUW 
ee sates \ Vao AINAVI Pr0alLoasNr 5 
s oe a. ee ee 
pi es a 
VEUALAOUTHD 

a TNTTS noe, 

See Viltd TAdid 
VNINTWOH | 


CoA Pl Bake FE 


THE SKELETON. 


THE term Skele/on, in its widest sense, is used to denote a 
system of hard parts forming a framework which supports 
or protects the softer organs and tissues of the body, and 
which may be either entirely external or superficial as re- 
gards those organs and tissues, or may be more or less 
embedded in enveloping softer structures. In the former 
case it is called an Hwvoskeleton, in the latter an Endoskeleton. 

It is of the Endoskeleton alone that this work proposes 
to treat, as in the class Mammalia the external skeleton, 
when it exists, performs a relatively subordinate part in the 
economy.! 

The branch of anatomy called Osteowogy is commonly 
restricted to a study of such parts of the endoskeleton as 
are composed of bony or osseous tissue, a tissue charac- 
terized by a peculiar histological structure and chemical 
composition, being formed mainly of a gelatinous basis, 
strongly impregnated with phosphate and carbonate of 
lime, and disposed in a definite manner, containing nume- 
rous minute nucleated spaces, or cavities called /acune, 
connected together by delicate channels called canaliculz, 


1 The Armadillos and their extinct allies are the only known mam- 
mals which have an ossified exoskeleton. 


8 THE SKELE TON. [eHAP: 


which radiate in all directions from the sides of the lacune. 
This structure is readily recognized when a thin section of 
bone is examined under a moderately high magnifying power. 

Parts composed of bone are, of all the tissues of the body 
(with the exception of the teeth), the most imperishable, 
often retaining their exact form and intimate structure ages 
after every trace of all other portions of the organization has 
completely disappeared; and thus in the case of extinct 
animals affording the only means of attaining a knowledge 
of their characters and affinities. 

It must, however, be remembered that, at one period of 
life, the parts composing the skeleton exist in a fibrous or 
a cartilaginous form, that their transformation into bone is 
a subsequent and gradual process, and that even in the 
Mammalia, though in a less degree than in some of the 
other Vertebrata, the whole of the internal skeletal system 
is never entirely osseous, but that portions may remain 
permanently in a cartilaginous or fibrous condition. 

The different bones composing the skeleton are con- 
nected together either by swtwres, or by moveable joczts 
or articulations. 

In the first, the edges of the bones are in close contact, 
often interlocking by means of projections of one bone 
fitting into corresponding depressions of the other, and are 
held together by the pervzosteum, or fibrous membrane invest- 
ing the bones, passing directly from one to the other, per- 
mitting no motion, beyond, perhaps, a slight yielditig to 
external pressure. The bones of the cranium are connected 
together in this manner. In old animals there is a great 
tendency for such bones to become joined together by 
the extension of ossification from one to the other and 
consequent obliteration of the suture. This process is 
called syzostosts. 


11. ] THE SKELETON. 9 


The various forms of joints may be arranged under two 
principal heads. In one, the contiguous surfaces of the 
bones are connected by interposed fibrous tissue, passing 
directly from one to the other, filling up the space between 
them, and allowing of only a limited amount of motion, as 
is the case with the bodies of the vertebree. 

The other and more frequent and more perfect form of 
joint is that in which the contiguous extremities of the bones 
are covered by a thin layer of very smooth cartilage, and 
surrounded by a capsular ligament, attached only round the 
edges of the articular surfaces, and which is lined by a 
synovial membrane, so called from its secreting a viscid 
lubricating fluid termed syzovza. The amount of motion 
permitted in these ‘‘ synovial joints ” varies according to the 
form of the opposed articular surfaces and the arrangement 
of the hgaments which hold them together. When the two 
surfaces are-nearly flat, and the bones firmly bound by strong 
short ligaments, as in those which compose the carpus and 
tarsus, the motion is reduced to an extremely slight gliding 
of one on the other. Joints in the form of a hinge, as at 
the elbow, allow of a free motion in one plane only. Ball 
and socket joints, as at the shoulder and hip, allow of the 
greatest variety of movements. ' 

The Endoskeleton is divided into an axial portion, be- 
longing to the head and trunk, and an afpendici/ar portion, 
belonging to the limbs. ‘There are also certain bones called 
splanchnic, being developed within the substance of some of 
the viscera. Such are the os cordis and os penis found in 
some Mammals. These, however, are more appropriately 
treated of with the anatomy of the organ of which they form 
a part. 

The Axial Skeleton consists of the vertebral column, the 
skull, the sternum, and the ribs. 


CHAPTER Tir: 
THE VERTEBRAL COLUMN. 


General Characters.—The Vertebral Column consists of a 
series of distinct bones called Vertebre, arranged in close | 
connection with each other along the dorsal side of the neck 
and trunk, andin the median line. It is generally prolonged 
posteriorly beyond the trunk to form the axial support of the 
appendage called the tail. Anteriorly it is articulated with 
the occipital region of the skull.’ 

The number of distinct bones of which the vertebral 
column is composed varies greatly among the Mammalia, 
the main variation being due to the elongation or otherwise 
of the tail. Apart from this, in most Mammals, the number 
is not far from thirty, though it may fall as low as twenty-six 
(as in some Bats) or rise as high as forty (Ayrax and 
Cholepus).? 

The different vertebrae, with some excep‘ions, remain 
through life quite distinct from each other, though closely 
connected by means of fibrous structures which allow of a 
certain, but limited, amount of motion between them. 


1 For the sake of uniformity, in all the following descriptions of the 
vertebral column, the long axis of the body is supposed to be in the 
horizontal position. 


* These numbers are not exact, owing to the uncertainty in the mode 
of reckoning the sacral vertebrze. 


CHAP.- III. | GENERAL CHARACTERS, II 


The exceptions are,—near the posterior part of the trunk, 
in nearly all Mammals which possess completely developed 
hinder limbs, two or more vertebrae become ankylosed 
together to form the “ sacrum,” the portion of the vertebral 
column to which the pelvic girdle is attached. As a rule, 
none of the other vertebrze are normally united by bone, 
but in some species there are constant ossific unions of 
certain vertebrae, more particularly in the region of the 
neck. ‘These will be specially noticed presently. 

Although the vertebrze of different regions of the column 
of the same animal, or of different animals, present great 
diversities of form, there is a certain general resemblance 
among them, or a common plan on which they are con- 
structed, which is more or less modified by alteration of 
form or proportions, or by the superaddition or suppression 
of parts to fit them to fulfil their special purpose in the 
economy. 

An ordinary vertebra (see Fig. 2) consists in the first place 
of a solid piece of bone, the body or centrum (c), of the 
form of a disk or short cylinder. The bodies of contiguous 
vertebree are connected together by a very dense, tough, and 
elastic fibrous material, called the zzfervertebral substance, of 
peculiar and complex arrangement. This substance forms 
the main, and in some cases the only, union between the 
vertebrz. Its elasticity provides for the vertebrz always 
returning to their normal relation to each other and to the. 
column generally, when they have been disturbed therefrom 
by muscular action. 

A process (/) rises on each side from the dorsal surface 
of the body. ‘These meeting in the middle line above form 
together an arch, surrounding a space or short canal (vc). 
As in this space lies the posterior prolongation of the great 
cerebro-spinal nervous axis, or spinal cord, it is called the 


12 THE VERTEBRAL COLUMN. (CHAP. 


neural canal, and the arch is called the seural arch, in con- 
tradistinction to another arch on the ventral surface of the 
body of the vertebra, called the hemal arch. ‘Vhe last is, 
however, never formed in mammals by any part of the 


vertebra itself, but only by certain bones, placed more or. 


less in apposition with it, and which will not here be con- 
sidered as parts of the vertebral column, strictly speaking. 


Fic. 2.—Anterior surface of human thoracic vertebra (fourth), $c body or centrum ; 
zc neural canal; Z pedicle and @ lamina of the arch; ¢ transverse process ; a2 
anterior zygapophysis. 

The lower portions of each side of the arch (/), usually 
thick and more or less vertical in direction, constitute its 
pedicles. 'The upper more compressed and more horizontal 
portions (/) are the d/amine. ‘The pedicles are usually 
notched in front and behind, but most deeply behind, to 
form the sides of the zutervertebral foramina for the trans- 
mission of the nerves issuing from the spinal cord. Occa- 
sionally the foramina for these nerves perforate the pedicles, 
instead of being truly intervertebral. 

The laminz meet in the median line above, at a more or 
less open angle. At the point of their junction there is 


' So called because it encloses the heart and the great central bloud- 
vessels, 


ss = - 


IIT. | GENERAL CHARACTERS: 13 


usually a single median process projecting dorsally, called 
the spenous process or neural spine. 

In most cases upon the anterior and posterior edges of the 
laminee of the arch are flattened, slightly projecting, more or 
less oval, smooth surfaces or facets, which in the natural state 
are covered with a thin layer of cartilage, and come into 
contact and articulate (by synovial joints) with the corre- 
sponding surfaces of the immediately antecedent and suc- 
ceeding vertebrae. These have been called by Professor 
Owen sygapophyses ; that placed on the front edge of the 
arch being the anéerior zygapophysts, that on the hinder edge 
the posterior zvgapophysis. As a general rule the latter have 
their faces directed downwards, overlying the upward 
directed anterior zygapophyses of the vertebra next behind. 
This is a useful rule to remember in ascertaining which is 
the front and which the posterior surface of a vertebra. 
Sometimes, especially in the lumbar region, the posterior 
zygapophyses have their faces directed outwards, in which 
case the corresponding anterior zygapophyses look inwards 
(Fig. 3, az). 

These articular surfaces on the arch constitute a second 
mode by which the vertebrz are united, and their size and 
conformation aid to regulate the amount of motion allowed 
between the component parts of the column. They are often 
entirely wanting when flexibility is more needed than 
strength, as in the greater part of the caudal region of 
long-tailed animals. 

In addition to the body and the arch, there are certain 
projecting parts called processes, more or less developed in 
different vertebrae. Many difficulties exist about the signi- 
fication, homologies, and terminology of these processes. 
Probably, when more is known of the development of the 
vertebree in a large series of animals, some further light will 


14, THE VERTEBRAL COLUMN. [CHAP. 


be thrown on the subject ; but at present it does not appear 
that there is that uniformity in the plan of construction of 
all vertebrae which has often been supposed, and definitions 
of the different parts applicable in every case have not yet 
been arrived at, and it may even be doubted whether this 
will ever be possible. 

The principal processes commonly met with are as follow:— 

F From the middle of the ‘upper (part ofthe aren 
process generally single, but sometimes bifid at the end, 
grows out vertically. This is the spznous process, or neural 
spine already mentioned ; about its homology in different 
vertebrae there never can be any question. It may however 
be completely absent, when the arch is round or smooth 
above, as in the cervical region in some animals; on the 
other hand, it may grow out into a very long conspicuous 
rod of bone, as in the anterior dorsal region of others. 

2. Occasionally a process grows in the median line from 
the under-surface of the body. This may be single and long 


Fic. 3.—Anterior surface of the lumbar vertebra of Hare (Lefus timidus). s spinous 
process ; 7#z metapophysis; @z anterior zygapophysis; ¢ transverse process; / 
hypapophysis. 


and slender, as in the anterior lumbar vertebrez of the Hare 
(Fig. 3, 2), or a sharp median ridge, as in the cervical verte- 
bree of many Ungulata and the cervical and caudal vertebre 
of the Ornithorhynchus, or double, as in the atlas vertebra of 


IIl. | GENERAL CHARACTERS. 15 


the last-named animal and the caudal vertebrze of many 
others. This is termed a Aypfapophysis. Most commonly 
there is not even a trace of any such process. 

3. From the sides of the lower part of the arch, or from 
the body, lateral processes project more or less directly out- 
wards. These are called ¢ransverse processes. There may be 
but one, or there may be two, superior and inferior, on each 
side of a vertebra. In the latter case the superior is some- 
times called a dafophyszs, and the inferior a parapophysis ; 
though it is questionable whether the processes to which 
these terms have been applied can always be regarded as 
strictly homologous. 

4. Besides these principal laterally projecting processes, 
there are often others arising from the side of the arch, more 


Fic. 4.—Side view of first lumbar vertebra of Dog (Canis _famzliaris), 2. s spinous 
process ; az anterior zygapophysis ; fz posterior zygapophysis ; #z metapophysis ; 
@ anapophysis; ¢ transverse process. 


especially developed in the lumbar region, though by no 
means constant even there. Of these there may be one or 
two on each side. They have often been called accessory 
Processes ; Dut in the more precise system of nomenclature 
introduced by Professor Owen, the one which is situated 
highest on the arch (see Fig. 4, m), projects more or less 


16 THE VERTEBRAL, COLUMN. [ CHAP. 


forwards as well as outwards, is usually thick and rounded, 
and is nearly always in relation with the anterior zygapo- 
physis, is termed meéapophysis ;' the one placed rather lower 
(Fig. 4, z), and which projects more or less backwards, and 
is generally rather slender or styliform, is called anapophysis. 

These, with the zygapophyses before mentioned, sometimes 
called oblique processes, but which are rather articular surfaces 
than true processes, are all the processes commonly met with 
on any Mammalian vertebra. 


Development of the Vertebre—The first indication of the 
formation of a vertebral column in the embryo is the 
appearance of a longitudinal przmeteve dorsal groove in the 
germinal membrane, the edges of which (damne dorsales) 
rise up and meet above, so as to convert the groove into a 
canal. From the tissue lining this canal (uppermost layer 
of the germinal membrane) the brain and spinal cord are 
developed, and in its walls are formed anteriorly the cranium, 
and posteriorly the vertebral column ; the canal itself be- 
coming the cerebral cavity and the neural canal of the spine. 

In the floor of this canal, formed by a horizontal lamina 
which separates it from another and larger, ventral or heemal 
canal (formed by the approximation in the middle line below 
of the Zamzne ventrales), a slender rod of peculiar structure 
is developed. This is the notochord or chorda dorsalts, 
around which the bodies of the future vertebrae are deve- 
loped. In the Mammalia it almost completely disappears at 
a very early period, traces only remaining in the axis of the 
intervertebral substance, though in many of the inferior 
Vertebrata it is persistent as a continuous rod for a longer 
period, and sometimes permanently. 


1 Tt is also called ‘‘ mammillary process” in some works on Human 
Anatomy. 


III. J DEVELOPMENT, 17 


The formation of the arches of the vertebre in the 
lamine dorsales is preceded by the appearance of dark- 
looking cellular masses called proto-vertebre or somatomes, 
corresponding in number, though not exactly in situation, to 
the future vertebrz, and which undergo a series of changes 
(for a description of which the student is referred to special 
treatises on embryology) out of which ultimately results a 
vertebra, similar in shape to that which it presents in adult 
life, but formed of a continuous piece of hyaline cartilage. 

The mode of ossification of this cartilaginous vertebra in 
the different groups of Mammals still offers an interesting 
field for investigation, but the following is a summary of the 
most important facts ascertained regarding it. 

Leaving out for the present the greatly modifted two 
anterior vertebrae, the atlas and the axis, which must be 
specially considered afterwards, and also the comparatively 
rudimentary vertebrae of the caudal region, each vertebra 
consists at one period of three pieces of bone, as distinct 
from each other, and remaining so for as long a period, as 
many of the separate elements of the skull. 

One constitutes the greater part, but usually not the whole, 
of the body or centrum. Each of the others forms one side 
of the arch, and usually more or less of the upper lateral 
part of the body. ‘These last ultimately unite to each other 
in the middle line above, and to the central piece on each 
side below. The line of union between them and the central 
piece is readily distinguishable in all vertebrze up to the time 
the animal is about half-grown, and is named by Professor 
Huxley the euro-central suture. (See Fig. 8, p. 27, 70s.) 

As a general rule all the processes (except the hypapo- 
physes) arise from the part of the vertebra situated above 
the neuro-central suture, but there are notable exceptions. 

The body of the vertebra is nearly always completed by 

C 


18 THE VERTEBRAL COLUMN. [CHAP. 


the addition of a thin disk-like efzphyszs at each end, which 
for a considerable period after it is fully ossified remains 
adhering by a rough surface to the central or main part 
of the body, and is easily separated from it by maceration. 
Its coalescence with the remainder of the body, especially in 
the thoracic region, is one of the last acts in the completion 
of the bony skeleton, and does not take place until after all 
the epiphyses of the limb bones are firmly united. Hence 
it may be taken as a safe indication that the animal is 
thoroughly adult. 

It must be noted that the epiphysis covers the whole 
surface of the end of the body, whether ossified from the 
centrum or the arch, and is therefore quite independent of 
the position of the neuro-central suture. 

These terminal epiphyses to the bodies of the vertebrz 
are peculiar to the Mammalia, but not found universally 
throughout the class, as they are wanting in the Ornitho- 
delphia and the Sirenia. In man, the highest apes, and also 
in some of the Didelphia, they have less solidity and import- — 
ance than in other Mammals, being often mere thin osseous 
rings, representing the circumferential portion only of the 
ordinary epiphysis. 

The various processes of the vertebree have been divided 
into those that are aufogenous, or formed from separate 
ossific centres, and exogenous, or outgrowths from either of 
the just-mentioned primary vertebral constituents. 

There can be no doubt but that an autogenous process 
of one vertebra of an animal may be serially represented 
by an exogenous process in another vertebra of the same 
animal ; and likewise that the corresponding processes of 


* Even the arches of some of the caudal vertebre appear to be 
ossified directly from the body, and not independently, as is the rule 
with the thoracic and lumbar vertebrz. 


111. J DEVELOPMENT. 19 


the same vertebra may be developed exogenously in one 
animal and autogenously in another. 

In nearly all the more prominent processes, moreover, 
whether formed by exogenous or autogenous ossification, 
the extreme tip remains cartilaginous for a considerable 
time ; and at a comparatively late period in developmental 
life (near the approach of maturity) a small ossific centre 
forms in it. This spreads through the cartilage, and then 
constitutes an epiphysis, which ultimately unites to, and 
becomes indistinguishably incorporated with, the remainder 
of the process.’ 

The spinous process is either formed by the coalescence 
of outgrowths from the two pieces forming the neural arch, 
or the greater part of it may be (as in the long spines of the 
anterior thoracic vertebree of Ungulates) formed by a very 
early autogenous ossification, which soon becomes united to 
the upper part of the arch. In either case it is usually com- 
pleted by an epiphysis of comparatively late ossification. 

There is one part connected with certain vertebre which 
‘requires some particular consideration, on account of the 
great modifications it presents, being in some regions a 
largely developed independent bone, articulated with the 
vertebra by synovial joints, and in other regions a small 
rudiment, early and firmly united to, and incorporated with, ~ 
the vertebra itself. 

The ribs in the thoracic region, though primarily formed 
from a rod of cartilage continuous with that of the vertebra, 


1 These epiphyses are sources of considerable difficulty in tracirg 
homologous parts, as it is questionable whether they should be treated 
as separate elements of the skeleton, and, if not, where to draw the 
line between an epiphysis and an element. They often appear mere 
conveniences of growth, as it were, being developed upon the end of 
a process when it is long, and being absent in a corresponding part of 
stunted dimensions. 

C2 


20 THE VERTEBRAL COLUMN. ~ [CHAP. 


always become distinct, independent, and moveably arti- 
culated bones ; after their original segmentation they can 
never be properly said to constitute part of the vertebra. 
But it frequently happens that in certain of the vertebrz 
anterior to the thoracic region, and in certain of those 
posterior to it, there are bony elements formed at an early 
period, which, though very different from ribs in the ordinary 
sense of the word, occupy a somewhat similar position 
in relation to the vertebrae to that which the nbs do in the 
thoracic region. These have hence been considered as 
modified conditions of the same part, and have been called 
Pleurapophyses by Professor Owen. 

Perhaps the clearest case of the presence of mb elements 
in the vertebree in any Mammal is afforded by the cervical 
vertebree of the Ornithodelphia, where the greater part of each 
transverse process ossifies separately from the rest of the ver- 
tebra, and remains for a long time only suturally connected 


Fic. 5.—Third cervical vertebra of a nearly full-grown Echidna (4. hystrix), the 
different pieces of which it is composed being slightly separated from one another. 
ma neural arch; ¢ centrum; ¢ transverse process; wv vertebrarterial canal ; xcs 
neuro-central suture. 


with it (Fig. 5). They thus closely correspond to the cer- 
vical nbs of reptiles, which are unquestionably homologous 
serially with the thoracic ribs. 

The anterior, or more properly inferior, bar of the trans 
verse process of the seventh, and occasionally of some of the 
- other cervical vertebrze in Man, is autogenously developed, 


III. ] DIVISION INTO REGIONS. 21 


and‘ has some characters by which it may be placed in the 
category of rudimentary ribs. ae 

The transverse processes of the anterior lumbar vertebree 
of certain Mammals, as the Pig, are originally autogenous 
elements, though coalescing very early with the rest of the 
vertebree. 

In the sacral region, the separate latera! ossifications which 
connect the vertebral column with the illum present many 
characters allying them to ribs. (See Fig. 6.) 


Fic. 6.—Anterior surface of first sacral vertebra (human), showing mode of develop- 
ment. za neural arch; ¢ centrum; # distinct (pleura,ophysial) ossification for 
attachment of ilium. 


Finally, the transverse processes of the caudal vertebree of 
some animals (as the Manati and Beaver) are separately 
developed, though it is doubtful whether this circumstance 
alone is sufficient to entitle them to be considered as costal 
elements. 

Division of Vertebral Column into Regions.—¥or con- 
venience of description the whole vertebral column has 
been divided into five regions, the cervical, thoracic,| lumbar, 
sacral, and caudal. 

This division is useful, especially as it is not entirely 
arbitrary, and in most cases is capable of ready definition, 


1 Generally called dorsal, but it would be better to reserve this term 
in morphology as relating to the upper surface of the body and opposed 
to ventral. 


22 VHE VERTEBRAL COLUMN. [CHAP. 


at least in the Mammalia; but at the contiguous extre- 
mities of the regions, the characters of the vertebrz of one 
are apt to blend into those of another region, either nor- 
mally, or as peculiarities of individual skeletons. 

1. The Cervéca/ region constitutes the most anterior por- 
tion of the column, or that which joins the cranium. 

The vertebre which belong to it are either entirely 
destitute of moveable ribs, or, if they have any, these are 
small, and do not join the sternum. 

As a general rule they have a considerable perforation 
through the base of the transverse process (the verte- 
brarterial canal, Owen), or, as it is sometimes described, 
they have two transverse processes, superior and inferior, 
which, meeting at their extremities, enclose a canal. (See 
hie. 9c Mie. 8, prog: and: Pigs..47 and 18, p..29,) 77 ihe 


Fic. 7.—Anterior surface of sixth cervical vertebra of Dog, 3. s spinous process 
az anterior zygapophysis ; ; v vertebrarterial canal; ¢ transverse process; 7’ its 
inferior lamella. 

however, rarely applies to the last vertebra of the region, in 

which only the upper transverse process is usually developed. 
The transverse process moreover very often sends down 

near its extremity a more or less compressed plate (cnvferior 

/amella, Fig. 7, ¢’), which being considered to be serially homo- 


10 es DIVISION INTO REGIONS. 


= 
logous with the ribs of the thoracic vertebrz (though not 
developed autogenously) is often called “ costal” or “ pleura- 
pophysial” plate. This is usually largest on the sixth, and 
altogether wanting on the seventh vertebra. 

The first and second cervical vertebrze, called respectively 
atlas and axzs, are specially modified for the function of 
supporting, and permitting the free movements of the head. 
They are not united together by an “intervertebral sub- 
stance,” but connected only by ordinary ligaments and 
synovial joints. 

The cervical region in Mammals presents the remarkable 
peculiarity that, whatever the length or flexibility of the 
neck, the number of vertebrae is the same, viz. seven, with 
very few exceptions, which will be particularized fur- 
ther on. 

2. The Zhoracc or Dorsa/ region consists of the vertebrz 
which succeed those of the neck, having ribs moveably 
articulated to them. ‘These ribs arch round the thorax, the 
anterior one, and most usually some of the others, being 
attached below to the sternum. 

The characters of the ribs and their mode of articulation 
with the vertebrze will be considered further on, but it may 
now be stated that in the anterior part of the thorax the 
vertebral extremity of each rib is divided into ‘head ” and 
“tubercle ;” that the former is attached to the side of the 
body of the vertebra, the latter to its transverse process ; 

‘and that the former (capitular) attachment corresponds to 
the interspace between the vertebree, the head of the rib 
commonly articulating partly with the hinder edge of the 
body of the vertebra antecedent to that which bears ts 
tubercle. Hence the body of the last cervical vertebra 
usually supports part of the head of the first rib. In the 
posterior part of the series the capitular and tubercular 


24 THE VERTEBRAL COLUMN. . * [CITAP. 


attachments commonly coalesce, and the nb is attached 
solely to its corresponding vertebra. 

3. The Lumbar region consists of those vertebra of the 
trunk in front of the sacrum (to be afterwards defined) which 
bear no moveable ribs. It may happen that as the ribs 
decrease in size posteriorly, the last being sometimes 
more or less rudimentary, the step from the thoracic to the 
lumbar region may be gradual and rather undetermined in 
a given species. But most commonly this is not the case, 
and the distinction is as well defined here as in any other 
region. 

As a general rule there is a certain relation between the 
number of the thoracic and the lumbar vertebree, the whole 
number being tolerably constant in a given group of 
animals, any increase of the one being at the expense of 
the other. Thus in all known Artiodactyle Ungulata there 
are 19 thoracico-lumbar vertebree ; but these may consist of 
12 thoracic and 7 lumbar, or 13 thoracic and 6 lumbar, or 
14 thoracic and 5 lumbar. 

The smallest number of thoracico-lumbar vertebre in 
Mammals occurs in some Armadillos, which have but 14. 
The number found in Man, the higher Apes, and most Bats, 
viz. 17, is exceptionally low ; 19 prevails in the Artiodactyles, 
nearly all Marsupials, and very many Rodents; 20 or 24 in 
Carnivora and most Insectivora, 23 in Perissodactyla. ‘The 
highest and quite exceptional numbers are in the two-toed 
sloth (Cholwpus), 27, and Hyrax, 30. 

The prevailing number of rib-bearing vertebrae is 12 
Or 13, any variation being generally in excess of these 
numbers. 

4. The Sacral region offers more difficulties of definition, 
especially at its posterior portion. 

‘Taking the human “ 0s sacrum” as a guide for comparison, 


HE | DIVISION INTO REGIONS. 25 


it is generally defined as consisting of those vertebre, between 
the lumbar and caudal regions, which are ankylosed together 
in the adult state to forma single bone. It happens, how- 
ever, that the number of such vertebree varies in different 
individuals of the same or nearly allied species, especially as 
age advances, when a certain number of the tail vertebra 
generally become incorporated with the true sacrum. 

A more certain criterion is derived from the fact that some 
of the anterior vertebrz of the sacral region have distinct 
additional (pleurapophysial) centres of ossification, between 
_ the body and the ilium (see Fig. 6, p. 21). To these perhaps 
the term sacral ought properly to be restricted, the remaining 
ankylosed vertebrz being called fsewdo-sacral, as suggested 
by Gegenbaur. Our knowledge of the development of the 
sacrum in different animals is not sufficient at present to 
apply this test universally, but it appears probable that two 
is the most usual number of true sacral vertebra, as thus 
defined in the Mammalia. 

5. The Caudal Vertebr@ are those placed behind the 
sacrum, and terminating the vertebral column. They vary 
in number greatly, being reduced to 5, 4, or even 3, in a 
most rudimentary condition, in Man, some Apes and Bats, 
and being numerous and powerfully developed, with strong 
and cornplex processes in many Mammals, especially among 
the Edentata, Cetacea, and Marsupialia. The highest 
known number, 46, is possessed by the African Long-tailed 
Manis. 


CHAPTER: oN: 


SPECIAL CHARACTERS OF THE CERVICAL VERTEBRZ IN. THE 
MAMMALIA. 


ORDER PRIMATES. — The human cervical vertebre (ex- 
cluding for the present the first and second) have short, 
wide, depressed bodies, hollowed in front from side to side, 
and behind from above downwards,' with wide neural canals, 
and short, broad, and usually bifid spines (considerably 
longer in the seventh vertebra than in the others), well 
marked, broad, flat, anterior, and posterior zygapophyses, 
and short, sub-bifid, widely perforated transverse pro- 
cesses. 

These vertebree are, as usual, developed mainly from three 
centres, one for each side of the arch, and one for the 
centrum (see Fig. 8), but it will be observed that the whole 
of the body is not formed from the latter, but that its lateral 
parts, with the transverse processes, are ossified from the 
arches. 

Besides these main centres of ossification there are thin 
and imperfect disk-like epiphyses on the ends of the body, 


! As before mentioned, the body is supposed to be placed horizontally, 
so that the same terms of relative position may be used as when speak- 
ing of the vertebral column of the ordinary less modified animals of the 
class. 


CHAP. ‘IvV.] CERVICAL, VERTEBRA: 27 


very late in making their appearance, and not joined until 
long after the rest of the vertebra is completed. A small 
epiphysis is also formed on the end of the spinous 
process. 


Fic. 8.—Sixth cervical vertebra of a child, 1. c centrum; z¢s neuro-central suture ; 
v vertebrarterial canal ; az anterior zygapophysis. 


Lastly, the inferior or ventral bar of the transverse process 
of the seventh vertebra is developed from a separate: centre 
of ossification, and occasionally the same part of the sixth 
and fifth has its own separate nucleus. This bar of bone is 
connected internally with a projection from the side of the 
body, ossified from the arch; externally with the end of the 
upper or true transverse process, which is an exogenous 
growth from the arch, so that it is attached to the vertebra 
entirely above the neuro-central suture. Occasionally it 
acquires an abnormal development, and grows into a con- 
siderable rib-like bone, in which case it is usually united at 
its distal extremity with the first thoracic rib. 

The first vertebra or atlas (Fig. 9) is little more than an 
oval ring, thickened on each side into the so-called “ lateral 
mass,” which bears an articular surface before and behind. 
The anterior surfaces are very large, elongated from above 
downwards, and hollowed for the reception of the condyles of 
the occiput. The posterior articular surfaces are subcircular, 


28 CERVICAL VERTEBRZE, [CHAP. 


flattened, or slightly-concave. ‘The transverse processes are 
short, stout, and perforated ; the arch presents scarcely a 
rudiment of a spinous process. On its anterior edge im- 
mediately above the articular surface is a deep notch or 
groove (g) of some importance, as it corresponds with the 
slight notch in front of the pedicle in other vertebrae, which 
contributes with the deeper notch in the hinder border of 
the pedicle of the preceding vertebra to form the “ inter- 


Fic. 9.—Human atlas, young, showing development, 3. za inferior arch ; as articular 
surface for occiput; ¢ transverse process; g g:oove for first spinal nerve and 
vertebral artery. 

vertebral” foramen for the exit of a spinal nerve, and because 
occasionally in man, and constantly in many animals, it 1s 
converted by a bridge of bone into a canal, through which 
the first cervical (or sudoccipita/) nerve passes out. The 
inferior arch of the atlas (cz) differs entirely from the bodies 
of the other vertebra, being a simple, depressed, slightly 
curved bar of bone, with a smooth facet on its meural or 
upper surface, for articulation with the odontoid process of 
the axis. 

The second cervical vertebra, axzs, cpistropheus, or vertebra 
dentata (Fig. 10), has a body terminating anteriorly in 
a large subconical median projection, the odontoid pro- 
cess (0), which is received into, and articulates with, the con- 
cavity of the inferior arch of the atlas. It is retained in its 


Iv.] MAN. 29 


place by means of a strong transverse ligament passing 
between the lateral masses of that bone, and separating its 
canal into an upper or neural portion for the passage of the 
spinal cord, and an inferior portion for the reception of the 
odontoid process. 

The axis has posterior zygapophyses placed on the arch, 
serially continuous with those of the rest of the vertebre, but 
its anterior articular facets, like those of the atlas, do not 
belong to the arch proper, but partly to the body and partly 
to the arch, and are therefore not exactly serially homologous 
with the zygapophyses of the other vertebrae. ‘The trans- 
verse processes are short, single, and perforated. The arch 
is high, with a stout bifid spine. 

The development of the atlas and axis offers some im- 
portant points for consideration. 

The arch of each is ossified from two centres, one on each 
side, as in other vertebre ; but if the axis is examined a year 


ij 
J ie 


De aren 

€ = (2 

Fic. 1o.—Diagram showing mode of ossification of human axis (hemal or ventral 
surface). 0 odontoid process, or centrum of atlas; c proper centrum of axis; 2d 


neural arch ; as anterior articu!ar surface; e e e epiphyses, completing the ends of 
the centra. 


or two after birth (Fig. ro), its body appears to be composed 
of two parts, one placed in front of the other, the first includ- 
ing the odontoid process and the anterior part of the body, 
the second all the remainder of the body. ‘The arch is 


30 CELERVICALWERTEB RZ. [CHAP. 


united to both. On the other hand, the atlas at the time 
of birth has nothing corresponding to the centrum of other 
vertebree, its inferior arch being still cartilaginous. 

It is therefore a generally received opinion among ana- 
tomists that the anterior ossification of the axis is essentially 
the body of the atlas, which unites with both arch and 
centrum of the vertebra behind it. It must be observed, 
however, that in its mode of ossification, at least in man, it 
differs from the centra of all the other vertebrz, as at one 
period it consists of two distinct lateral pieces, which after 
a while coalesce in the middle line.’ The usual disk-lke 
epiphyses of the vertebral bodies are represented by one 
at the posterior extremity of the body, by a small osseous 
nodule which completes the odontoid process in front, and 
by some irregular ossifications found between the two main 
portions of which the body is composed. 

The inferior arch of the atlas ossifies soon after birth 
from one or more centres, and the resulting piece of bone 
(Fig. 9, 7a) ultimately unites with the two pieces forming 
the neural arch about the same time as that at which they 
join together in the middle line above. ‘This piece may 
probably be regarded as a detached “ hypapophysial” seg- 
ment of the first vertebral centrum, the remainder of which 
forms the odontoid portion of the body of the axis. 

The cervical vertebree of the other PRiMATES resemble 
those of man generally, the most noticeable deviations being 
the following :— 

In the atlas the groove for the first cervical nerve is usually 
converted into a foramen; and a median hypapophysial 
tubercle or spine often projects backwards from its inferior 
arch under the axis (especially in AZycetes and Lagothrix). 

The spinous processes, especially of the third, fourth, 
fifth, and sixth cervical vertebree, are immensely elongated 


Iv. J CARNIVORA. 31 


in the Gorilla, and considerably so in the Chimpanzee and 
Orang. These processes as a rule are not bifid, as in Man, 
but occasionally (as in A/jrcefes) they are trifid, having a pair 
of lateral backward-projecting processes developed near 
their extremity.’ 

The inferior lamellae of the transverse processes are 
generally larger proportionally than in man, especially in the 
Lemurina. Inthe seventh vertebra, the transverse processes 
vary much as to their perforate or imperforate condition. 

In the Carnivora, the atlas (Fig. 11) has very deep 
anterior articular surfaces for the condyles of the skull. ‘The 


Fic. 11.—Inferior surface of atlas of dog, 3. sv foramen or first spinal nerve ; 
v vertebrarterial canal. 


first spinal nerve passes through a complete foramen. The 
transverse processes are large, wing-like, flattened from above 
downwards, and perforated by the vertebrarterial canal. 

_ The axis (Fig. 12) has a long conical odontoid process, 
and a large compressed neural spine, greatly extended from 
before backwards, and especially produced forwards. 

The remaining cervical vertebrze have small, narrow, com- 
pressed, usually simple spines, gradually lengthening to the 
seventh, and large transverse processes, with greatly developed 
inferior lamellz (see Fig. 7, pp. 22) especially large in the 
fifth and sixth. In the latter the lower edge of this lamella 


1 These are named hyferapophyses by Mr. Mivart, who has called 
particular attention to them: ‘‘On the Axial Skeleton in the Pri- 
mates :” Proc. Zool. Soc. 1865, p. 545. 


y 


32 CERVICAL VERTEBRA. [CHAP. 


is frequently hollowed in the middle, and produced at each 
extremity, so that the transverse process has a trifid appear- 
ance. This is especially marked in the Fe/7de. The trans- 
verse process of the seventh vertebra has no inferior lamella, 
and its base is imperforate. 


Fic. 12.—Side view ot axis of Dog. 3. s spinous provess; 0 odontoid process; fz 
posterior zygapophysis ; ¢ tramsverse process ; wv vertebrarterial canal. 


Metapophyses are generally more or less developed on the 
cervical vertebrae of the Carnivora, and there are also in 
some genera small backward projecting tubercles (Ay ferapo- 
physes, Mivart) situated on the laminz of the arch, rather 
internal to the posterior zygapophyses, not usually found in 
other vertebre. 

In the INsEcTivorA, the cervical vertebree vary consider- 
ably in their characters. ‘The atlas has. usually short trans- 
verse processes. Generally the spinous process of the axis 1s 
large and prominent, and that of the other vertebre very 
small, but in Centefes and Potamoga/le they are all more or less 
elongated. The neural arches in some (as A/yogale and 
Sorex) are reduced to mere filaments. In the mole (7Za//a) 
the transverse processes of the fourth, fifth, and sixth 
vertebrae are much expanded antero-posteriorly, and overlap 
each other. Large single hypapophyses are developed from 
the inferior surface of most of the cervical vertebre in the 
Shrews (Sorex) and some of their allies, and in Gadeopithecus 


1V.] RODENTIA, 33 


each vertebra bears at its hinder end a pair of hypapophysial 
tubercles. 

In the CHIROPTERA all the cervical vertebre are broad, 
very short from before backwards, with slender neural arches 
from which (except in the axis) no distinct spinous processes 
are developed. In certain forms (as Vesperugo) some of the 
vertebrae have distinct double hypapophysial spines project- 
ing backwards. 

In the RopDENTIA the atlas has usually broad, moderately 
long, wing-like transverse processes. ‘The odontoid process 
is long and slender; the spinous process of the axis is much 
developed, while as a rule that of the other cervical vertebree 
is exceedingly small. The transverse processes of the fifth 
and sixth have large inferior lamelle ; that of the seventh 
is sometimes perforated at the base (as in Lefus), and 
sometimes imperforate (as in Wydrocherus). 

In the Capybara ({/ydrocherus) and some others, the side 
of the arch of the atlas is perforated near its anterior border 
for the exit of the first spinal (sub-occipital) nerve, and also 
near its hinder border for the second cervical nerve. 

In the Jerboas (Yzpus) a very exceptional condition of 
the cervical vertebrz occurs. The atlas is free, but all the 
- others are ankylosed together by both bodies and arches, 
and the bodies are very wide and depressed, as in the 
Armadillos. 

Among the UNcutata, the atlas (Fig. 13) in the ecora is 
very long, with deep articular. cavities for the occipital con- 
dyles. ‘The transverse processes are not wide, but much 
extended from before backwards, and flattened from above 
downwards. Each is perforated by a foramen (s7’) which gives 
exit to the inferior division of the first cervical nerve, but not 
by the vertebral artery, which usually enters the neural canal 
between the arches of the second and third vertebre. The 

D 


34 CERVICAL VERTEBRA. CHAE: 


odontoid process ot the axis (Fig. 14) 1s of peculiar shape, 
being like a spout, or hollow half-cylinder, with a prominent 


Fic. 13.—Inferior surface of atlas of Red Deer (Cervus elaphus). sn foramen for 
superior branch of first spinal nerve ; sv’ foramen for inferior branch of the same 


nerve. 


sharp semicircular rim. The canal for the second cervical 
spinal nerve pierces the lamina of the axis near its anterior 
border. The other vertebrae have more or less elongated 


Fic. 14.—Anterior surface of axis of Red Deer, %. 0 odontoid process ; sx foramen 
for second spinal nerve ; fz posterior zygapophysis. 


bodies, which are opésthocwlous, i.e. concave behind and 
convex in front. They are keeled below, the keel being often 
developed into a hypapophysial spine posteriorly; the neural 


spines are moderately long, and inclined forwards. The 
transverse processes of the fifth, and especially of the sixth 


Iv. | UNGULATA. 35 


have large inferior lamellee. That of the seventh is usually 
imperforate. 

In the Giraffe the bodies of the cervical vertebrze are very 
long. The transverse processes are short, but so extended 
from before backwards as to become divided into two, one 
at the anterior and one at the posterior end of the vertebra. 
That of the seventh is perforated. 

In the Zy/opoda (Camels and Llamas) the vertebrarterial 
canal passes obliquely through the anterior part of the 
pedicle of the arch, being in its posterior half confluent with 
the neural canal. A similar condition occurs in AZacrau- 
chenia, an extinct South American Perissodactyle Ungulate. 

The Suzza and Tragulina differ from the remaining exist- 
ing Artiodactyles in the form of the odontoid process, which 
is conical ; while on the other hand the Horse and Tapir 
among the Perissodactyles have this process wide, flat, and 
hollowed above, approaching the form it presents in the 
Ruminants. In the Pig, the broad pedicles.of all the cervical 
vertebree are perforated by canals for the passage of the 
upper division of the spinal nerves. 

The bodies of the cervical vertebree in the Rhinoceros, 
Tapir, and Horse are markedly opisthoccelous, but in the 
Pig and Hippopotamus very slightly so. 

In the Horse the bodies of the cervical vertebre are 
elongated, with a strong keel and hypapophysial spines. 
The neural laminz are very broad, the spines almost obso- 
lete, except in the seventh, and the transverse processes not 
largely developed. The seventh is not perforated by the 
vertebrarterial canal. 

In the Rhinoceros, on the other hand, the bodies are 
comparatively short, and not keeled, the laminz narrow, the 
spines well marked, and the transverse processes greatly 
developed, especially those of the atlas. 

D2 


36 CERVICAL VERTEBRA. [CHAP. 


In the Elephant (order ProposcIpEA), .the atlas much 
resembles the human atlas. The axis has a short conical 
odontoid process, a very massive spine, broad above and bifid 
posteriorly. The bodies of the other vertebree are very short, 
flattened, sub-circular disks, very slightly opisthoccelous. 
Excepting the seventh they all have short spinous processes, 
and short, broad, and largely perforated transverse processes. 
The seventh has a high spine, an imperforate transverse pro- 
cess, and on the hinder edge of its body a very distinct arti- 
cular cavity for the head of the first rib. In the young animal 
this is divided into two equal parts by the neurocentral 
suture. 

In the order SrRENTA, the Dugong (/alzcore) has seven 
cervical vertebrae, as in the Mammalia generally. The atlas 
has short imperforate conical transverse processes. The axis 
has a high arch and massive neural spine, a short rounded 
odontoid process, and very rudimentary transverse processes. 
The others have short and wide bodies, small spines, and 
irregularly developed transverse processes, often not com- 
pletely enclosing a vertebrarterial canal. 

The Rhytina, a large animal of this order, which became 
extinct towards the close of last century, had also seven 
cervical vertebrae, and the Miocene Hadlitherium had the 
same number. 

The Manatis (genus J/anatus), of which there are two 
well-marked species, one inhabiting the west coast of 
Africa, and the other the east coast of Central and South 
America, never have more than szx vertebrz in the cervical 
region. ‘These resemble generally those of the Dugong, 
having short and wide bodies, and very irregular transverse 
processes. In a specimen of JZ. senegalensis, in the 
Museum of the College of Surgeons, the second and third 
are ankylosed by their bodies, and the neural arches of most 


Cv CETACEA: 37 


of the others are widely open above. In the skeletons of JZ. 
americanus, 11 the same museum, the vertebrez are all free, 
and the arches, though slender, are complete, and with very 
slightly developed spinous processes. 

In the Cefacea the seven cervical vertebrz usually found 
in the Mammalia are always present, though often so short 
and blended together, that it is not easy at first sight to re- 
cognize their existence. In some genera of both sub-orders 
all the vertebree are free, though never allowing of much 
motion between them ; but more commonly certain of them 
are firmly united together by bone. Even where the atlas 


Fic. 15.—Section through middle line of united cervical vertebrz of Greenland Right 
Whale (Balena mysticetus), }. « articular surface for occipital condyle; e¢ epi- 
physis on posterior end of body of seventh cervical vertebra ; sz foramen in arch 
of atlas for first spinal nerve; x arch of atlas; 2 3 4 5 6 conjoined arches of the 
axis and four following vertebrz ; 7 arch of seventh vertebra. 


and axis are separate the odontoid rarely forms a distinct 
process (it is most distinct in Platanista), but still it is devel- 
oped from an ossific centre of its own, as in other Mammals. 


38 CERVICAL VERTEBRA. [CHAP. 


Among the JZ stacocetz,in the Right Whales (genus Balena) 
the whole of the seven cervical vertebree are usually united 
into one mass by their bodies, though sometimes the seventh 
is free. The arches are also more or less united above, 
_though generally not in a continuous mass. Small slit-like 
openings between the narrow pedicles of the arches permit 
the exit of the cervical spinal nerves, and in the adult condi- 
tion afford the only indication by which the number or the 
united vertebrae can be ascertained. Already before birth 
most of the bodies have coalesced, and it is even doubtful 
whether they ever exist in a separate condition. 

The Fin Whales or Rorquals (genus avenopiera) present 
a totally different condition of cervical vertebre, as these are, 
as a rule, all distinct and free, though occasionally, as an 
individual peculiarity, an irregular ankylosis may take place 
between two or more of them.’ 


Fic. 16.—Anterior surface of atlas of common Fin Whale (Lalenoptera musculus), 4's. 
sz foramen for first spinal nerve. 


In the common large Fin Whale cf our coasts (4. 
musculus) the atlas (Fig. 16) has short, stout, conical, imper- 
forate transverse processes. ‘The axis (Fig. 17) has a broad 
oval body, high massive arch, very short odontoid process, 


1 See Professor Struthers ‘‘On the Cervical Vertebrze and _ their 
Articulations in Fin Whales.” (ournal of Anatomy and Physiology, 
November 1872.) 


Iv.] CETACEA, 39 


and very wide, oblong wing-like transverse processes directed 
somewhat backwards, and with an oval perforation near the 


Fic. 17.—Anterior surface of axis of common Fin Whale (Galenxoptera musculus), y's. 
o odontoid process. 


base. The other cervical vertebrw (Fig. 18) have similar 
broad, very short bodies, small arches, without spines, and 
very long transverse processes, composed of a slender upper 


Fic. 18.—Anterior surface of fourth cervical vertebra of the same animal, ;/s;. az ante- 
rior of zygapophysis ; ¢ upper transverse process ; ¢’ lower transverse process. 


and lower bar, widely separated at their bases, but united at 
their extremities so as to enclose a very large space between 
them. In the seventh the upper process only exists, and the 
lower one is occasionally imperfect in the sixth.t In very 
young animals these processes are formed only of cartilage ; 


1 Professor Turner has shown that, in a fatal Balenoptera sibbaldi, 
the inferior transverse process of thé seventh is present in a cartilagi- 
nous condition. (Journal of Anatomy and Physiology, May 1871.) 


40 CERVICAL VERTEBRA [CHAP. 


and as ossification takes place gradually from within out- 
wards, and does not reach the outer extremity until the 
animal approaches maturity, specimens are frequentiy met 
with in museums, which, instead of completely annular 
transverse processes, show only truncated upper and lower 
bars. In some species, however (as in AZegaptera longimana), 
most of the cervical vertebrae remain permanently in this 
condition. 

Among the Odontocetz, all the cervical vertebree are free in 
the Gangetic Dolphin (//atanzsfa), and in the allied South 
American genera /yéa and Ffontoporia, also in the Nar- 
whal (Afonodon) and the Beluga, or the White Whale. In 
most of these genera the atlas has a large hypapophysial 
process, projecting under and articulating with the body of 
the axis, which develops no distinct odontoid. In the 
Narwhal irregular ankyloses between the bodies of the cervical 
vertebrze are very frequent. In all the other De/phinide 
(including Delphinus, Orca, Pseudorca, Globicephalus, Pho- 
cena, &c.), at least the first and second cervical vertebrze 
are united by both body and spine, and most commonly 
some of the succeeding vertebre are joined to them. If 
any are free, it is always those situated most posteriorly, 
and they have extremely thin, sub-circular disk-like bodies, 
and irregular and comparatively rudimentary transverse 
processes. 

In Ayperoodon, the whole of the cervical vertebre are 
ankylosed together. In the other Ziphioids several of the 
posterior vertebrz are free, and the allied Cachalot, or Sperm 
Whale (Pyseter), presents a condition not met with in any 
other known Cetacean: the atlas is free, and ail the other 
neck vertebree are completely united. 

Among the various members of the order EpENTaTA, the 
cervical vertebrz present very different conditions. 


1v.] MARSUPIALIA. 4l 


In the Armadillos (Dasysodide) the bodies are extremely 
short, broad, and depressed, and several are commonly anky- 
lesed together; the corresponding neural arches being also 
united, the neural and vertebrarterial canals form continuous 
tubes. The orifices for the spinal nerves perforate the united 
pedicles. The atlas is always free. The vertebre that are 
united are the second and third, or the second, third, and 
fourth, and in some species the fifth also. The spinous 
process of the axis is very large, but the neural arches of the 
hinder free vertebrze are extremely narrow, and the spinous 
processes rudimentary. The transverse process of the 
seventh has an inferior lamella, nearly as large as that of 
the sixth, but it is usually not perforated. 

In Orycteropus, the Pangolins (A/anzs), and the Anteaters 
(Myrmecophaga), the neck vertebree are more normal in form, 
and are not ankylosed. In the last-named genus, the verte- 
brarterial canal of several of the vertebrz perforates the 
pedicle obliquely, and enters the neural canal posteriorly, 
much as in the Camels. 

Among the leaf-eating Edentates, or Sloths, the neck 
vertebrae present some remarkable peculiarities, especially 
as to number. 

All the known species of three-toed Sloths (genus Lrady- 
pus) have nine cervical vertebree, z.e. nine vertebree in front of 
the one which bears the first thoracic rib (or first mb con- 
nected with the sternum, and corresponding in its general 
relations with the first rib of other Mammals), but the ninth, 
and sometimes the eighth, bears a pair of short moveable 
ribs. The eighth is perforated by the vertebrarterial canal, 
but not the ninth. 

The common species of two-toed Sloth (Cholepus didac- 
tylus) has seven cervical vertebrae, but a closely allied 
species (C. hoffmannzz) has but six. 


42 CERVICAL VERTEBRA. [CHAP. 


In the very heterogeneous order MaArsupratia (sub-class 
Didelphia) the cervical vertebre vary much in their characters, 
though the number is always seven, as in the great majority 
of the Mammalia. 

One of the most important variations is in the mode of 
ossification of the atlas. In the Wombat (Phascolomys), 
Koala (Phascolarctos), Phalangista, and Kangaroo (Macropus), 
there is no distinct ossific nucleus in the inferior arch of the 
bone, which remains either permanently open in the middle 
line below, or (as in some of the smaller Kangaroos) is com- 
pleted by the union of prolongations ot the arches inwards. 
This, however, is not the case with the carnivorous Mar- 
supiais. In the Thylacine (see Fig. 19) there is a distinct 
heart-shaped piece of bone in the centre of the inferior arch 
of the atlas, which appears never to become united to the 
remainder, as it is still attached by ligament in skeletons 
otherwise perfectly mature, and is commonly lost in mace- 


Fic. 19 —Inferior surface of atlas of Thylacine (Thylacinus cynocephalus), 2. h dis- 
tinct ossification in centre of inferior arch, with pointed hypapophysial pro- 
jection. 


ration. In Perameles and Dide/phys the atlas is completely 
ossified below by a wide intermediate piece, quite as in 
ordinary Mammals. 

As to the other vertebre, in the Kangaroos the transverse 
processes are long and slender, and (including the seventh) 
have avery small perforation close to the base. The inferior 
lamella arises near the base of the process, and is very 


Iv.] MONOTREMATA. 43 


large in the sixth, but generally absent in the seventh 
vertebra. 

In the Wombat, the bodies are wide and depressed. The 
transverse processes are perforated in all ; the inferior lamella 
of the sixth is much developed antero-posteriorly. The 
spines of all are rather short. 

In Perameles /agotis the greater part ot the transverse pro- 
cess of the axis is ossified separately from the rest of the 
vertebra, and remains sometime distinct, as in the Mono- 
tremata. In this genus, as in the other carnivorous Marsu- 
pials, the inferior lamelle of the transverse processes of the 
fourth, fifth, and sixth vertebrae, but especially of the latter, 
are particularly large. 

Some species of American Opossums (as Dzedelphys 
virginiana and its nearest allies) have the spinous processes 
of the second, third, fourth, and fifth cervical vertebrze, very 
high, square, and massive, and being closely applied to each 
other by flattened surfaces, form a solid wall of bone along 
the top of the neck. 

In both genera of MonotremMata (sub-class Ornitho- 
delphia) the cervical vertebrae are seven in number, and in 
both the inferior arch of the atlas is completely ossified, 
apparently from a separate centre ; but in Ornzthorhynchus 
a large bifurcated hypapophysis is developed, which is quite 
wanting in Echidna. 

In Ornithorhynchus also all the other cervical vertebrae 
have a single median hypapophysial spiue, equally wanting 
in Lchidna. 

In both, the axis has a high compressed spine, and the 
odontoid portion remains long distinct from the true centrum 
of the bone. In both, the transverse processes are of auto- 
genous formation, and remain suturally connected with the 
remainder of the vertebra until the animal is nearly full- 


44 CERVICAL VERTEBRE, [CHAP Ve 


grown (see Fig. 5, p. 20); that of the axis is still distinct 
in an adult Orncthorhynchus. Though in this respect they 
present an approximation to the Sauropsida (Reptiles and 
Birds), they differ from that group, inasmuch as there is not 
a gradual transition from. these autogenous transverse pro- 
cesses of the neck (or cervical ribs, as they may be con- 
sidered) into the thoracic ribs, for in the seventh vertebra 
the costal element is much smaller than in the others, 
indicative of a very marked separation of neck from thorax, 
not seen in the Sauropsida 


ge 


CHAPTER: V. 


SPECIAL CHARACTERS OF THE THORACIC AND LUMBAR 
VERTEBRA. 


Ir will be most convenient to consider the vertebre of 
these two regions together. 

In Man, there are seventeen trunk vertebra, twelve 
thoracic or rib-bearing, and five lumbar. 

The bodies increase in size from before backwards, and 
also change their form. ‘The first is like a cervical ver- 
tebra, broad and depressed. ‘They soon become more 
compressed, especially at the lower part, so as to be subtri- 
angular when seen from one end (Fig. 2, p. 1%); after the 
middle of the thoracic region they become more circular in 
outline, and in the lumbar region they are wide transversely. 
The ends of the bodies are flat or slightly concave. 

The neural canal does not alter greatly in size throughout 
this region, though it doés somewhat in form. In the first 
vertebra it is wider in proportion to its height than in any 
of the others. 

The arches have comparatively narrow pedicles, arising 
from the anterior half of the body, deeply notched behind, 
for the canal for the exit of the spinal nerves. ‘The laminz 
are broad. The spines are moderately long, subequal 
throughout the series, rather slender, and sloping backwards 


46 TRUNK VERTEBRAE. [CHAP. 


in the thoracic region; broader (in the antero-posterior 
direction) and more upright in the lumbar region, and pre- 
senting but scarcely any indication of that convergence 
towards a point in the posterior thoracic region so fre- 
quently seen in other Mammals. They are generally simple 
and slightly dilated at their ends; but in the lumbar region, 
the posterior edge is often more or less bifid. 

The zygapophyses are well developed throughout. In 
the thoracic region they are oval, flat facets, looking pretty 
nearly directly upwards (the anterior) and downwards (the 
posterior): the anterior, developed on the top of the pedicle 
and projecting forwards, being supported by the “ oblique 
process ;” the posterior is placed on the under-surface of the 
hinder part of the lamina. In the lumbar region, their form 
and position change, the anterior having their outer edges 
turned upwards, and supported by a short rounded meta- 
pophysis (s#amdilary process). The posterior ones have 
undergone a corresponding change, so that their faces, instead 
of looking downwards, are directed obliquely outwards ; they 
are also much curved. 

The transverse processes project throughout the series 
from the arch, near the junction of the pedicle with the 
lamina. In the greater part of the thoracic region they are 
tolerably long, project somewhat upwards, and slightly for- 
wards, and are dilated and tuberous at the extremities, on 
the under surface of which (except in the two last) they show 
a smooth concave facet for the attachment of the tubercle of 
the rib. In the posterior part of the thoracic region they 
are shorter, and begin to resolve themselves into three dis- 
tinct processes, generally conspicuous in the first lumbar. 
One of these projects outwards, and, elongating in the second 
and third lumbar, it forms its principal transverse process. 
One projects upwards and forwards, by the side of the an- 


v] PRIMATES. 47 


terior zygapophysis ; this is the metapophyszs, or mammillary 
process. ‘The other projects backwards, and represents in 
a rudimentary condition the process so largely developed in 
many animals called anapophysis. It gradually becomes 
smaller in the second and third lumbar vertebree, and gene- 
rally disappears in the fourth. 

The lumbar transverse processes are thus not serially 
homologous with the thoracic ribs, but with the part of the 
transverse process of the thoracic vertebree to which the 
tubercle of the rib is attached, and are complementary to 
the ribs, becoming greatly augmented in size directly these 
cease. Neither are they normally developed autogenously.! 

The sides of the bodies of the thoracic vertebrae bear 
facets for the articulations of the heads of the ribs. Except 
the last three or four, each vertebra supports a portion of the 
heads of two ribs, having a large facet near its anterior edge 
(placed partly on the body and partly on the side of the 
pedicle) for the head of its own rib (ze. the rib which arti- 
culates also with the transverse process), and on the hinder 
border of the upper angle of the body a small facet to re- 
ceive the anterior edge of the succeeding rib. In the hinder 
part of the thoracic region the rib is connected only with 
its corresponding vertebra, and not with the one in 
front. 

Among the remaining Primates, 19 1s the prevailing 
number of trunk vertebrz, of which usually 12 to 14 bear 
ribs. The Gorilla and Chimpanzee (genus Zvoglodytes), 
agree with Man in having 17. The Orang (Szmza) has 
usually but 16. The Gibbons (//y/odates) and Spider 


1 There are several specimens in the College Museum which show 
the co-existence, on the first lumbar vertebra, of a rudimentary (supple- 
mental) rib, with a transverse process serially homologous with the 
transverse processes of the other lumbar vertebree. 


48 TRONK VERTEBRZE. [CHAP. 


Monkeys (Aée/es) have mostly 18. Among the Lemurina, 
Loris and Vycticebus have as many as 23 or 24. 

Of thoracic vertebree, the Gorilla and Chimpanzee have 
13, the Orang 12, the Gibbons usually 13 ; other Old World 
Monkeys mostly 12; the American Monkeys from 12 to 15 ; 
the Lemurs from 12 to 16. 

As a general rule the vertebral column, taken as a whole, 
is straighter than it is in Man, showing a much less marked 
sigmoid curve. 

Except in the most anthropoid Apes, and a few others, the 
spinous processes of the anterior thoracic vertebree lean 
backwards, and those of the lumbar and some of the poste- 
rior dorsal vertebree forwards, so that they converge to a 
point near the hinder part of the thoracic region, sometimes 
called “the centre of motion” of the vertebral column.! 
This may be between two vertebrae, but more often there 1s 
one, which has an upright spine, towards which the others 
are directed ; this is the “‘ antzclinal vertebra.” It is at this 
point that the thoracic vertebrae begin to change their 
characters, and assume those of the lumbar vertebrz ; and 
the simple elongated transverse processes break up as it 
were into the metapophyses, anapophyses, and lumbar 
transverse processes, all of which are conspicuous in these 
animals. 

The transverse processes of the lumbar vertebrz are 
usually placed lower on the sides of the vertebre than 
in Man. 

In Galago the hinder edges of the neural spines of the 
lumbar vertebree bear a pair of backward-projecting pro- 
cesses, which clasp the anterior edge of the succeeding 

1 This disposition of the spines of the trunk vertebre is still more 


marked in many of the inferior mammals, especially the terrestrial 
Carnivora. 


v.] INSECTIVORA. 49 


spine. Similar processes are developed, but to a less ex- 
tent, in the Howling Monkeys (A/yeetes) and in Lagothrix. 

The foramina for the exit of the spinal nerves, instead of 
being “intervertebral,” perforate the pedicles of the arches 
in the Potto (Perodicticus). In the same genus, two or three 
of the anterior thoracic vertebree have very long slender 
spinous processes, which in the living animal project beyond 
the general level of the skin, forming distinct conical 
prominences, covered only by an exceedingly thin and 
naked integument. ; 

In the Carnivora, the trunk vertebree are nearly always 
20 Or 21 innumber. The genera Felis, Canis, and Viverra 
have 13 thoracic and 7 lumbar, Hyena 15 and 5, Mustela, 
Nasua, Procyon, and Ursus 14 and 6, Meles 15 and 5; 
Mephitis has the exceptionally high number of 16 and 6, 
and Mellivora but 14 and 4. Among the Seals, Cystophora 
and Ofaria have 15 and 5, Zrichecus 14 and 6, and Phoca 
hae atch 5: 

The spines of the anterior thoracic vertebrz are long and 
slender, and slope back to about the eleventh (the anziclinaZ), 
after which they are shorter, thicker (from before backwards), 
and lean forwards. From this point also metapophyses and 
anapophyses become distinctly developed; the latter are 
especially large in the Fe/zde. ‘The lumbar vertebre have 
long transverse processes directed forwards and rather 
downwards, and short, stout, compressed spinous pro- 
concesses. 

In the Seals, the trunk vertebrae present much the same 
characters, but the anapophyses are usually but slightly 
developed, or may be altogether absent, and the spinous 
processes show no convergence to a ‘‘ centre of motion.” 

Among the INsecTivora, the number of the trunk vertebrze 
varies much in the different genera, from 18 (13 thoracic and 

E 


50 TRUNK VERTEBRA. [CHAP. 


5 lumbar) in Zupaza, 19 (13 and 6) in Zalpa and most 
Soricide, 19 (14 and 5) in Galeopithecus, 21 (15 and 6) in 
Erinaceus, 22 (19 and 3) in Chrysochloris, to 24 (19 and 5) 
in Centetes. 

There are also great differences in the development of the 
processes of the vertebrze, which appear to accord with the 
diversities in the habits and movements of the animal. The 
transverse processes of the lumbar vertebrz are very short 
in the comparatively slow moving, running, or burrowing 
Hedgehogs (Zrcnaceus), Shrews (Sorex) and Moles (Zaipa), 
but they are very long, broad, and inclined downwards in the 
jumping Macroscelides and Rhynchocyon, where the lumbar 
muscles are greatly developed and the hinder extremities 
_disproportionately large. 

In the Mole, there are distinct, small, oval, flat ossicles on 
the under-surfaces of the interspaces between the lumbar 
vertebrae. Similar ossicles, but in a more rudimentary con- 
dition, are occasionally found in the same situation in some 
other Insectivora, as the Hedgehog, but not in any other 
Mammals. 

The usual number of thoracic and lumbar vertebre in the 
CHIROPTERA Is 17, being either 12 and 5, or less commonly 
tr and 6. ‘The transverse processes of the lumbar vertebre 
are almost obsolete, as are also the spinous processes through- 
out the series. 

Among the RopENTIA, the most prevalent number is 109 ; 
but it falls as low as 16 (13 thoracic and 3 lumbar) in /2ber 
stbeticus, and rises as high as 23 (17 and 6) in Cafromys, and 
even as 25 (17 and 8) in Loncheres. 

The characters of the vertebrze vary much in the different 
genera, as among the Insectivora. In the Hares (genus 
Lepus) the anterior thoracic vertebree have long slender 
spinous processes ; the lumbar vertebree (see Fig. 3, p. 14) 


v.] STRENTA. 51 


have very long and slender transverse processes directed 
downwards and forwards and widening at their extremities ; - 
long metapophyses projecting upwards and forwards, small 
anapophyses, and remarkably long, single, compressed 
median hypapophyses. These latter are not found in the 
Rodentia generally. 

In the UNcuLaTa, the bodies of the trunk vertebrez are 
generally slightly opisthoccelous. The spinous processes in 
the anterior thoracic region are exceedingly high and com- 
pressed. ‘The transverse processes of the lumbar vertebrz 
are long, flattened, and project horizontally outwards or 
slightly forwards from the arch. The metapophyses are 
moderately developed, and there are no anapophyses. ‘The 
canals for the exit of the spinal nerves frequently pierce the 
pedicle of the neural arch. 

In the Artiodactyle sub-order the number of thoracic and 
lumbar vertebre together is always 19, though the former 
may vary from 12 to 15. Among the Perissodactyles the 
number 23 is equally constant, the Horse and Tapir having 
18, and the Rhinoceros rg thoracic vertebree. 

Some species of Hyrax have as many as 22 thoracic and 
8 lumbar vertebree, making altogether 30, the highest num- 
ber in any terrestrial Mammal. 

The Elephants have 23 in all, 19 or 20 of which bear ribs. 

In the order SIRENIA, the thoracic vertebree are numerous 
and the lumbar very few; thus the Dugong (//adzcore) has 
19 thoracic and 4 lumbar, and the Manati (AZanazus) 17 and 
2. The bodies are rather triangular, being compressed and 
keeled below, and in the young state have no distinctly 
ossified terminal epiphyses. The bodies of all the thoracic 
vertebrze bear articular facets for the heads of the ribs. 
The spinous processes are not very high, but the zyga- 
pophyses are well developed throughout the series. The 

E 2 


52 TRUNK VERTEBRA. [CHAP. 


metapophyses are rudimentary, and there are no distinct 
anapophyses. 

As there is no sacrum in the Ceracra the lumbar region 
passes directly into the caudal, and they can only be dis- 
tinguished by the presence of ‘ chevron bones” in the 
latter. 

The thoracic vertebrae vary in number from 9 in Hyper- 
oodon, to 15 and occasionally 16 in some Fin-Whales 
(Balenoptera), and the lumbar vertebrze from 3 in /zza (the 
Amazonian fresh-water Dolphin) to 24 or even more in some 
of the true Dolphins (De/phznus). 

The bodies are short in the anterior part of the thoracic 
region, but posteriorly become more or less elongated and 
cylindrical. ‘Their terminal epiphyses are strongly ossified 
disks, very distinct in young animals, but coalescing com- 
pletely with the rest of the body in adult age. The spinous 
processes are high and compressed. ‘The zygapophyses are 
very little developed, and only found in the anterior thoracic 
region. ‘The metapophyses are distinct (see Fig. 20, m), 
placed at first near the ends of the transverse processes, 
but gradually rising on the arch, are ultimately transferred 
to the sides of the anterior edge of the neural spine, from 
which they project forwards, clasping between them the 
hinder edge of the spine of the vertebra in front. 

In most Cetacea the transverse processes in the anterior 
thoracic region arise rather high on the side of the neural 
arch of the vertebra, but in the hinder part of the same 
region become gradually placed lower, until finally they are 
transferred to near the middle of the side of the body, 
which position they occupy in the lumbar region (see Fig. 
20). The transverse processes of the lumbar vertebree are 
thus evidently serially homologous with the transverse pro- 
cesses of the anterior dorsal vertebra, which, in their turn, 


v.] CETACEA. 53 


J 


continue backwards the upper series of cervical transverse 
processes. 

In the Physeteride (comprising Physeter, Hyperoodon, 
Ziphius, and the allied forms) a very different and peculiar 
arrangement occurs (Fig. 21). The transverse processes in the 
anterior thoracic region (¢) are placed quite similarly to those 
of the ordinary Dolphins ; but passing backwards, instead 


Fic. 20.—Anterior surface of vertebrae of Dolphin (Globicephalus melas), +. a fifth 
thoracic ; B seventh thoracic; ¢ eighth thoracic ; D first lumbar; x rib; 7z meta- 
pophysis; ¢ transverse process. ‘lhe dotted lines indicate the position of the 
neuro-central suture. 


of changing their position on the vertebrz, they gradually 
become smaller, and finally disappear ; while, simultaneously 
with their diminution in size, other processes (¢’) rise from 
the body of the vertebra, in the situation of the capitular 
attachment of the rib, which, rapidly increasing in length, 
become continuous serially with the lumbar transverse pro- 
cesses. In two or three vertebree the two co-exist (Fig. 21, 


54 TRUNK VERTEBRA. [car, 


Band c), resembling the upper and lower transverse pro- 
cesses of the neck, and sometimes even meeting at their 
extremities so as to enclose a canal. The lumbar transverse 
processes in this case therefore are not serially homologous 
with the transverse processes of the anterior thoracic region, 
and of the upper transverse processes of the neck, as in the 
former case, but rather with the lower transverse processes 


Fic 21.—Anterior surface of vertebra of Sperm Whale (Piyseter macrocephalus), »'y- 
A eighth thoracic; B ninth thoracic; c tenth thoracic; D fifh lumbar; * mb; 
m Ietapophysis ; ¢ upper transverse process ; ¢’ lower transverse process. 


of that region ; and yet tried by every other test, the special 
homology of the transverse processes of the lumbar vertebree 
of a Dolphin (Fig 20, p ¢) and a Sperm Whale (Fig. 21, D Z) 
is perfectly evident. 

The mode of ossification of the thoracic and lumbar 
vertebree of the Cetacea appears, so far as it has been 


v.] EDENTATA. 55 


ascertained, to differ from that of all other Mammals, inas- 
much as the neuro-central suture (see Fig. 20) is always 
placed a little above the junction of the arch and the body, 
the whole of the latter, with any process which may arise 
from it, being ossified from the central nucleus. Conse- 
quently, in the thoracic vertebrze of the Dolphins, the trans- 
verse process is anteriorly an outgrowth from the arch, then 
partly from the arch and partly from the body, and finally 
from the body alone—a condition quite unknown in other 
Mammals. i 

It would appear, from the conflicting statements on the 
subject, that the transverse processes of the lumbar region 
are sometimes ossified autogenously, and sometimes exo- 
genously from the centrum. 

The members of the order EDENTATA present some great 
peculiarities in the condition of the trunk vertebree, especially 
those of the lumbar region. 

As to numbers, the Three-toed Sloths (Gradypus) have 
20 altogether (either 17 and 3, or 15 and 5); and the Two- 
toed Sloths (Cholepus) have sometimes as many as 24 tho- 
racic and 3 lumbar, making altogether 27 trunk vertebre. 
The Great Anteater (AZyrmecophaga) has 18 (15 and 3); the 
little Two-toed Anteater (Cyclothurius), 17 (15 and 2). The 
Armadillos have 15 to 19, the Pangolins (A/anzs) commonly 
18 (13 and 5), and the Cape Anteater (Ovycteropus) 21 (13 
and 8). 

The vertebral column of the Sloths is remarkable for the 
extremely broad, flat laminze and short neural spines, lying 
backwards on the next succeeding vertebrz, throughout the 
whole column down to the sacrum. All the processes are 
very short, and the spines are bifid in the lumbar region. 

In Sradypus a small (anapophysial) process projects 
backwards from the hinder edge of the transverse process 


56 TRUNK VERTEBRA. [CHAP. 


of each lumbar vertebra, having on its inner surface a facet, 
which articulates with a corresponding facet on the anterior 
edge of the arch of the succeeding vertebra, below the 
ordinary zygapophysis. 

In Megatherium, Myrmecophaga, Cycothurus, and Dasypus 
(in fact, all the remaining American Edentates), a disposition 
thus slightly indicated in the Sloths, is carried out to a great 
extent, and results in a very complex and altogether peculiar 
method of articulation between the vertebre. 

It will be most convenient to describe it from one species, 
the Great Anteater (AZyrmecophaga jubata), but it is the same 
in principle in all the above-named genera. 


Fic. 22.—Side view of twelfth and thirteenth thoracic vertebre of Great Anteater 
(Myrmecophaga jubata), 3. ue metapophysis; 7c facet for articulation of tubercle 
of rib; cc ditto for capitulum of rib; az anterior zygapophysis; az! additional 
anterior articular facet; Zz posterior zygapophysis; #2! and Zz? additional pos- 
terior articular facets. 


The anterior thoracic vertebre articulate in a perfectly 
normal manner by large anterior and posterior zygapophyses. 
These retain the horizontal position of their facets through- 
out. On the eleventh dorsal vertebra, the upper surface of 
the backward projecting process which bears the posterior 
zygapophysis (#z) below, develops an articular surface 


v.] EDENTATA. . 57 


(~z') which looks upwards and articulates with a corre- 
sponding downward directed process (az!) developed on the 
upper part of the arch of the following vertebra, rather 
below the metapophysis (7). Thus the vertebra has a 
process projecting backwards, with flattened articular facets 
on its upper and under surface, fitting into a deep recess 
on the anterior edge of the arch of the vertebra behind, 
and the articulation is now by two zygapophysial surfaces 
on each side of the arch instead of one. 

In the thirteenth thoracic vertebra a third articular facet 
(ps7) is developed on the hinder margin of the lamina of 
the arch, still higher than the last additional one (J:'), 
and separated from it by a deep notch. This looks mainly 


Fic. 23.— Posterior surface of second Fic. 24.—Anterior surface of third lum- 
lumbar vertebra of Great Anteater, 3. bar vertebra of Great Anteater, 3. 
z transverse process; £2 posterior zyga- Z transverse process ; 7 metapophysis ; 
pophysis; #2!, Az2, and #23, additional az anterior zygapophysis ; @z', az*, and 
posterior articular facets. @z3, additional anterior articular facets. 


outwards, and articulates with a corresponding facet (az”, 
Fig. 24) on the anterior edge of the arch of the fourteenth 
vertebra, placed to the inner side of the metapophysis, which 
is now situated on a process projecting forwards into the 
notch between the two upper articular facets of the ante- 


58 TRUNK VERTEBRA. [CHAP. 


cedent vertebra. So that there are now three distinct arti- 
culations connecting the arches of the vertebre on each 
side, the processes of the vertebrze which bear them inter- 
locking in a “ tenon and mortise ” fashion. 

This condition continues as far as the second lumbar, in 
which, in addition to these three facets, a fourth (/°) is 
developed on the under surface of the hinder edge of the 
transverse process near its outer extremity, which articulates 
with a similar facet (az?) on the upper surface of the 
transverse process of the third lumbar, so that there’are now 
four pairs of articular facets, or zygapophyses, on each arch. 
The same occurs also between the third lumbar and the 
first sacral vertebra. 

In the Armadillos the lumbar metapophyses are very long, 
and project upwards, outwards, and forwards, supporting 
the bony carapace, while the broad transverse processes 
are exceedingly reduced. 

An allied extinct genus, Glyptodon, had the greater 
number of the trunk vertebrze completely ankylosed, a con- 
dition altogether unique in the Mammalia. 

In neither of the Old World Edentates, Manzs and 
Orycteropus, is there any development of the articular facets 
other than the ordinary zygapophyses. In the former genus, 
the metapophyses (contrary to the usual rule) project rather 
backwards than forwards. The anterior zygapophyses of the 
lumbar and posterior thoracic region are largely developed, 
and very concave, completely embracing the semicylindrical 
surfaces of the posterior zygapophyses. There are no 
distinct anapophyses. In Orycteropus the lumbar vertebrze 
are numerous (8), with carinated bodies, long and slender 
spines inclined forwards, long, broad, and flat transverse pro- 
cesses pointing forwards and downwards, well developed 
metapophyses and rudimentary anapophyses. 


v.] EDENTATA. 59 


In the MarsupiAuia, the number of thoracico-lumbar 
vertebree is invariably tg, although there are some apparent 
exceptions, in which the last lumbar assumes the form of a 
sacral vertebra. The rib-bearing vertebrz are always 13, 
except in the Koala (Phascolarcios), which has but 11, 
and one species of Wombat (Phascolomys vombatus), which 
has 15. ‘The Hairy-nosed Wombat (P. /atifrons) has the 
ordinary number. 

In the Kangaroos, the lumbar vertebre have largely 
developed metapophyses and anapophyses, and moderate- 
sized transverse processes much curved forwards. 

‘In the running and jumping Bandicoots (Perameles) the 
lumbar vertebree have very slender, long, forward-directed 
spines, and long transverse processes. In the climbing 
Opossums (Dide/phys), on the other hand, the spines are 
very short and broad from before backwards. 

The Monorremata agree with the Marsupials in the total 
number of trunk vertebre, but those that bear ribs are more 
numerous, viz. 16 in Lchidna, and 17 in Ornithorhynchus. 

The spinous and transverse processes are very short, and 
the ribs have no articulation with the latter, but are 
attached to the bodies only, the greater part of the articular 
surface being below the neuro-central suture, the reverse of 
what occurs in the higher Mammals. In the thoracic ver- 
tebree the canals for the exit of the spinal nerves perforate 
the neural arch. 


CHAPTER Wi. 


SPECIAL CHARACTERS OF THE SACRAL AND CAUDAL 
VERTEBRA. 


Sacral Vertebre.—The difficulties in defining the sacral ver- 
tebree have been noticed at p.24. ‘Their essential character 
is best illustrated by tracing it up from the simple condition 
it presents in the tailed Amphibians (as AZenofoma). In these 
animals a series of similar small straight ribs are moveably 
articulated to the ends of the transverse processes of all 
the trunk vertebre, which are not distinctly divisible into 
separate regions. To the distal extremity of one of these 
the ilium is attached. This vertebra with its rb thus 
constitutes the “sacrum,” and the ilium is clearly seen not 
to be a “ pleurapophysis,” as it is sometimes called, or any 
part of a vertebra, but a something distinct and superadded. 
In the Crocodiles there are two vertebrae with strongly 
developed rib-like bones connecting them to the ilum, and 
remaining long only suturally united to their vertebree. 

The inferior ossification of the transverse processes of the 
true sacral vertebree in Mammals (see Fig. 6, p. 21) 1s clearly 
of the same nature, though more rudimentary in character, 
and coalescing at an earlier period with the remainder of the 
vertebra. It isnot yet known that it exists in all Mammals, 
but this may be considered probable, as it is certainly found, 
at least in the first sacral vertebra, in such different forms as 


CHAP. VI.] CAUDAL VERTEBRA. 61 


Man, the Chimpanzee, Orang, Cat, Sheep, Elephant, Sloth, 
and Wombat. 

The ankylosis of additional vertebre in the Mammalia is 
probably related to the greater fixity and more complete 
attachment of the pelvis to the vertebral column in this 
class ;1 for the innominate bone is not only articulated 
by its iliac portion to the true sacral vertebre, but it has 
also a posterior connection with the vertebral column by 
its ischial portion, by means either of very strong ligaments, 
or in some cases by bony union.’ 

In Man there are usually five ankylosed vertebre, con- 
stituting the “‘os sacrum” of anthropotomy, but only two, or 
sometimes three, have distinct costal elements. The re- 
mainder may be called pseudo-sacral, and belong more pro- 
perly to the caudal series. ‘The sacrum as a whole is broad, 
strongly curved in the longitudinal direction, with the con- 
cavity downwards, and its anterior extremity forms with the 
body of the last lumbar vertebra a more prominent “ sacro- 
vertebral angle” than in other Mammals. 

In the Gorilla, Chimpanzee, and Orang, there are 
generally five ankylosed vertebrz, to which the last lumbar 
not unfrequently becomes united in old animals. The 
whole sacrum thus formed is long and narrow, gradually 
tapering posteriorly, and much less curved than in Man. 
In the other Monkeys, there are usually two or three, 
rarely four, ankylosed vertebre; the first two, or true sacrals, 
are broad, and behind these the sacrum suddenly contracts. 


1 This is carried to a still greater extent in birds. 

2 Hence the following definition of the sacrum: ‘‘ The posterior 
limit of the sacral region is characterized, not by the union of the 
different osseous pieces, which varies according to age, but by the place 
of insertion of the ischio-sacral ligaments.” (A. MILNE EDWARDS, 
Famille des Chevrotains, p. 52.) 


62 CAUDAL VERTEBRA. [CHAP. 


In the Zemurina the number of united vertebree varies 
from 2 to 5. 

In the CaRNIVORA, as a general rule, there appears to be 
but one true sacral vertebra, though one or more are ankylosed 
to it behind, especially in the Bears and Seals, where as 
many as 4 or 5 may be united by bone in old animals. In 
the Dog there are usually 3 ankylosed vertebre. 

In most UNcGuLatTa and RopDENTIA the sacrum consists of 
one broad vertebra joining the ilia, and a series of narrow 
ones, varying in number with age, gradually diminishing in 
width, ankylosed to it behind. 

In the Beaver among Rodents, the Cape Anteater (Orye- 
teropus) among Edentates, and the Wombat among Marsu- 
pials, the sacrum consists of numerous anky!csed vertebre, 
with widely-expanded transverse processes, which are longer 
in the hindermost vertebree, and nearly meet the ischia. 

In most other EpENTATA, as the Sloths, Anteaters, and 
Armadillos, this modification is carried further, and the 
transverse processes of the hinder pseudo-sacral vertebree 
form a complete bony union with the ischia, converting 
into a foramen what is usually the sacro-sciatic notch. 
In some of the Armadillos as many as 10 vertebre are 
thus most firmly fused together, and with the innominate 
bones. 

In MaRsuPIALIA usually but one vertebra supports the iliac 
bones, though another is commonly ankylosed with it. 

In the Monotremata, the Echidna has 3, and the Orni- 
thorhynchus 2 ankylosed vertebre. 

The Ceracea having no iliac bones, have no part of 
the vertebral column specially modified into a sacrum ; but 
in the StRENIA, the rudimentary ilia are attached by liga- 
ment to the ena of the transverse processes of one vertebra, 
which may hence be regarded as sacral. 


VI.] GENEKAL CHARACTERS. 63 


Caudal Vertebra.—The vertebre of the tail vary greatly 
in number and in characters in different animals. When 
it is well developed, as, for example, in the long-tailed 
Carnivora, from one of which the accompanying figures 


Fic. 25.—Anterior surface of third caudal vertebra of Leopard (Feds leopardus), 3. 
az anterior zygapophysis ; fz posterior zygapophysis ; #z metapophysis; ¢ trans- 
verse process. : 

are taken, the anterior vertebre (Figs. 25 and 26) are 

comparatively short and broad, with complete neural 

arches, though without distinct spines, prominent metapo- 
physes, and anterior and posterior zygapophyses (the latter 


Fic. 26.—Upper surface of the third caudal vertebra of Leopard, %. az anterior 
zygapophysis ; £2 posterior zygapophysis ; # metapophysis ; ¢ transverse process. 


especially being raised on pedicles), and well-developed 
single transverse processes. But a gradual change takes 
place in these characters (see Figs. 27 and 28), the body 
lengthens out and becomes more and more cylindrical ; the 


64 CAUDAL VERTEBRA. [CHAP. 


neural arch diminishes and finally disappears, leaving for a 
while a pair of processes at each extremity of the vertebra, 
the remains of the parts of the arch which bore the zygapo- 
-physes; the transverse process is much reduced, and con- 
fined to the posterior extremity of the body, a second one 
appearing at the anterior extremity. Even these rudiments 
of processes gradually cease to be perceptible, and nothing 
is left but a cylindrical rod of bone, representing the centrum 
alone of the vertebra. These diminish in size towards the 
apex of the tail, the last being usually a mere rounded nodule. 


iii Ny 


LLL 


TD. 


WE ff fy 
WE 


3) t 
Fic. 27.—Anterior surface of twelfth Fic. 28.—Upper surface of twelfth caudal 
caudal vertebra of Leopard, 3. vertebra of Leopard, 4. mz metapo- 
metapophysis: # processes serially physes ; # processes serially continuous 
continuous with those which support with those which support the posterior 
the posterior zygapophyses in the an- zygapophyses in the anterior vertebra. 
terior vertebree ; / hypapophyses. The z transverse process; 2’ anterior trans- 


process on the side of the body be- verse process. 
tween 7z and / is the anterior trans- 
verse process. 


Connected with the under-surface of the caudal vertebree 
of many animals which have the tail well developed, are 
certain bones, formed more or less in the form of an in- 
verted arch (Fig. 29), called chevron bones (French, Os en V ; 
German, Unterbogen; hamapophyses, Owen). These are 
always situated nearly opposite to an intervertebral space, and 
are generally articulated both to the vertebra in front and the 


vI.J GENERAL CHARACTERS. 65 


vertebra behind ; but sometimes chiefly or entirely either 
to one or the other. They are usually articulated movably 
to prominences (ypapopryses) on the lower surface of the 
body of the vertebra, but occasionally become ankylosed to 
it. They ossify from two centres, one on each side, which 
usually coalesce in the median line below, though not unfre- 
quently, especially at the beginning and end of the series, 
where they are less developed, the two lateral portions remain 
permanently separate. They serve to give a larger surface of 


Eres 29.— Anterior surface of fourth caudal vertebra of Porpoise (Phecena com- 


wiunis), 4. s spinous process; #2 metapophysis ; ¢ transverse process ; 4 chevron 
bone. 


attachment for the inferior muscles of the tail, and also to 
protect the caudal vessels, which run within the canal formed 
by the series of these bony arches. They are always best 
developed near the anterior extremity of the tail, and are 
never found under the posterior rudimentary vertebree. 

In Man the caudal vertebree are quite rudimentary ; 
usually 4 in number, all ankylosed together, and constituting 

F 


66 CAUDAL VERTEBRA. [CHAP. 


the coccyx, or os coccyg?s, of anthropotomy. ‘The first is some- 
times ankylosed to the sacrum. 

Among the Szmziva there are but 4 to 5 caudal vertebre 
in the Anthropoid Apes and in the Barbary and Black 
Macaques, no more than ro in some Baboons, and as many 
as 32 in Semnopithecus, and 33 in some of the Spider Mon- 
keys (Afe/es). 

In the latter the tail is prehensile, and the vertebre are 
broader and altogether more strongly developed than in the 
weak, pendant, though almost equally long tails of the Oid 
World monkeys. 

Chevron bones are found in all except those species that 
have the tails quite rudimentary. ‘hey are most fully de- 
veloped in AZe/es, where the extremities are often bifurcated. 
They are attached to a pair of projections on the anterior 
end of the lower surface of the vertebra. 

In the Zemurtna, the number of the caudal vertebre 
varies from 5 to 29. 

Among the Carnivora, the Bears have very short tails, 
with from 8 to ro vertebrae, the Seals from 9 to 14; some 
of the Lynxes have but 13, but most of the animals of the 
order have tails of moderate or great length ; the greatest 
number of vertebrze being found in Paradoxurus, which 
may have as many as 36. 

Chevron bones are usually not much developed; they 
are articulated (sometimes ankylosed) to the front ends of 
the vertebra, as in the Primates. 

In the Insecrivora, the tail is very variable. It is short 
and simple in Zyzzaceus and Centetes, long in Solenodon, 
Gymnura, Potamogale, Tupata and Rhynchocyon ; in the 
last-named genus the chevron bones are well developed and 
bifid. 

In the Cuiroprera, the tail is sometimes exceedingly 


sel RODENTTA. 67 


rudimentary, as in Desmodus ; sometimes elongated, but 
composed of long, simple, slender, cylindrical vertebral 
bodies; and generally enclosed in the interfemoral cuta- 
neous expansion. 

Among the different members of the order RODENTIA, 
there are great differences in the condition of the caudal 
vertebrae. 

InpthetHares; Guinea: Pigs; Capybara, &c., the tail is 
almost rudimentary. In the Cape Jumping Hare (Pedetes) 
it is nearly as long and powerful as that of a Kangaroo, 
with well-developed chevron bones. 

In the true Porcupines the tail is generally short ; but in 
some allied genera (Tree Porcupines) it is much elongated 
and prehensile. 

In the Beaver (Cas¢or) there are 25 caudal vertebrz, all 
short, broad, and depressed, and with wide transverse pro- 
cesses, becoming double (anterior and posterior) about the 
middle of the tail, not by development of a new process, 
but by gradual division of the one existing in the anterior 
region. 

In the UncutatTa, the tail is variable in length, but of 
simple character and function; it is never prehensile, 
nor has it ever chevron bones, although occasionally, as 
in the Ox, a pair of well-developed hypapophyses may be 
produced so as to meet in the median line, enclosing a 
small canal.1 The vertebre are most numerous in the 
Oxen, and least so in some Deer, especially A/oschus, in 
which animal the tail is quite rudimentary. 

The Elephant has a long tail, composed of 31 vertebre 
of simple character, without chevron bones. 

In the Hyrax the tail is almost rudimentary. 

1 The Eocene Axoflotherium appears to have had chevron bones, 
beneath the vertebrze of its long tail. 

F 2 


68 CAUDAL VERTELERZ. [CHAP. 


As the tail is the principal organ of locomotion in the 
CETACEA, it is always very well developed, and consists of 
numerous (from 18 to 30) vertebree. 

Chevron bones are always present, and of simple character, 
though with long compressed median spines (see Fig. 29, 
p. 65). They are mainly attached to the posterior extremity 
of the vertebra immediately in front of them. 

The characters of the caudal vertebree in the various 
animals of the order are tolerably uniform, the tail having 
the same function in all. In the anterior part of the region 
the bodies are very massive and cylindrical ; the arches have 
high spines, with metapophyses on their anterior edges, and 
the transverse processes are tolerably long, and directed 
straight outwards. In passing backwards the arches and all 
the processes gradually disappear, and the bodies become 
much compressed, and elevated vertically. Suddenly a 
change takes place (at the spot where the end of the 
vertebral column becomes enclosed in the horizontal, 
laterally extended cutaneous expansions, constituting the 
‘“flukes”’ of the tail), and the ‘vertebrae altogether: alter 
their characters, becoming much smaller, wide transversely 
and depressed. There is always one vertebra which is 
transitional in its character between these two forms. Most 
of the caudal vertebree are perforated by a vertical canal on 
each side, at first passing through the base of the transverse 
process, but posteriorly through the body of the vertebra 
itself. This transmits an ascending branch of the caudal. 
artery. : 
The SrrENIA have numerous, much depressed caudal 
vertebrae, with wide transverse processes, gradually dimin- 
ishing in length from the commencement towards the 
apex. They are thus very different from those of the 
Cetacea. 


vi] EDENTATA, 69 


Among the Epentata, the Sloths have a quite rudi- 
mentary tail, consisting of from 6 to ro depressed vertebree 
without chevron bones. 

In the allied A/egatherium the tail was greatly developed, 
with long processes and large chevron bones, as is the 
case with nearly all the Entomophagous Edentates, but 
mostly so in the Pangolins (JZanzs), one species of which 
(AZ. longicauda) has 46 tail vertebrz, the highest number 
known in any Mammal. Cyclothurus has a prehensile tail of 
‘40 vertebrae. The little Ch/amydophorus has a rather short 
tail of 15 vertebrae, remarkable for being expanded, de- 
pressed and spatulate towards the end, the transverse pro- 
cesses actually increasing in size instead of gradually 
diminishing, as is almost universally the case. 

The chevron bones are usually much developed. They 
are Y-shaped, having long, simple, compressed spines in 
Orycteropus ; V-shaped in Manis and most Armadillos ; but 


Fic. 30.—Anterior surface of third caudal vertebra of Great Armadillo (Priodontes 
gigas), y. s spinous process; #2 mctapophysis; @z anterior zygapophysis; ¢ trans- 
verse process; /# chevron bone with diverging processes. 


in Priodontes, they have wide, diverging, lateral processes, 
instead of a median spine. ‘They are attached rather to 
the vertebra in front than to that behind them. 


70 CAUDAL VERTEBRA. [CHAP. 


In the MarsupIatA, as might be supposed in so hetero- 
geneous a group, there is great diversity in the condition of 
the caudal vertebree. 

In the Wombat (Phascolomys) and Koala (Phascolarctos) 
the tail is comparatively rudimentary. 

In the Kangaroo, on the other hand, it is very large, and 
serves as an organ of support when standing upright. It is 
composed of from 21 to 25 vertebree, the first few with short 
bodies and large processes’; afterwards the bodies lengthen 
out, becoming cylinders contracted in the middle. The 
zygapophyses soon cease, but the metapophyses continue 
longer. ‘The neural arch is not continued longer than about 
the middle of the tail ; the transverse processes are gradually 
placed further and further back on the vertebra, and then a 
new one arises near the anterior end, so that they become 
double. ‘ 

The chevron bones are placed quite between the verte- 
bree, so that it is difficult to say to which they most 
properly belong. In the proximal part of the tail their 
free edge is compressed and develops a process forwards 
and backwards, giving a hatchet shape when seen side- 
ways. Further back they also send out broad processes 
laterally, so as to be cruciform, with a flat inferior 
surface. 

In some Marsupials the tail is prehensile, as in the 
Opossums (Dide/phys), with from 19 to 35 vertebre, and the 
Phalangers (Phalangista), with from 21 to 31. 

Chevron bones are generally present in the tails of all 
the Marsupials, except the Wombat and Koala. In the 
Thylacine they are few, and comparatively rudimentary. 

The tails of the two animals composing the order 
MoNoTREMATA differ considerably. 

The Echidna has 12 caudal vertebre. These have no 


vie] MONOTREMATA. 71 


hypapophyses, but there are two single median chevron 
bones near the middle of the tail, more like the lumbar 
subvertebral ossicles of the Mole than ordinary chevron 
bones. ‘The Ornithorhynchus has 20 or 21 caudal vertebre, 
with wide transverse processes, a single median hypapo- 
physis, and no chevron bones. 


CHAP TER® Wl; 


THE STERNUM. 


THE Sternum of Mammals is a bone, or generally a series 
of bones, placed longitudinally in the mesial line, on the 
inferior or ventral aspect of the thorax, and connected on 
each side with the vertebral column by a series of more or 
less ossified bars called ribs.! 

It is present in all Mammals, but varies much in cha- 
racter in the different groups. 

When in its usual and most complete form (see Fig. 31), 
it may be divided into three parts, called respectively,— 

1. Presternum, or ‘‘manubrium sterni” of human ana- 
tomy. 

2. Mesosternum, body of the sternum or gladiolus. 

3. Awphisternum, xiphoid or ensiform process of the ster- 
num. 

The mesosternum is usually composed of several distinct 
segments, which may become ankylosed together, but mcre 
often permanently retain their individuality, being con- 
nected either by fibrous tissue or by synovial joints. 


? For much valuable information upon the structure and development 
of the sternum, see W. K. Parker’s ‘‘ Monograph on the Shoulder-girdle 
and Sternum of the Vertebrata,” published by the Ray Society, 1868. 


CHAP. VII.] GENERAL CHARACTERS. 73 


The ribs are attached to the sides of the sternum : the 
first pair to the presternum ; the second to the presternum 
and the mesosternum at their point of junction; the 
remainder to the mesosternum, opposite the interspaces 
between each segment, though two or more pairs are often 
clustered round the last segment. ‘The xiphisternum bears 
no ribs. 

Development.—The osseous sternum is preceded by a 
continuous or non-segmented piece of cartilage ; and as the 


Sp /0 


Fic. 31.—Human sternum and sternal ribs, }. As presternum; 7s mesosternum ; 
xs xiphisternum; c point of attachment of clavicle; 1 to 1o the cartilaginous 
sterna! ribs. 


portion of the body in which this is developed is formed 
by the union in the middle line of the two “ ventral 
lamine” of the embryo, traces of this original median 
division are generally seen in very young sterna, and are 


74 THE STERNUM. [CHAP. 


often persistent through hfe in the form of fissures or 
fenestrae in the middle line of the sternum. Each segment 
ossifies from a single nucleus, or from two nuclei placed 
one on each side of the middle line, and which usually 
become blended together in the course of growth. Some- 
times epiphyses are added to the ends of the segments. 
The terminal portion of the xiphisternum generally remains 
cartilaginous through life. 

Special Characters of the Sternum in the various Orders. 
Order Primates.—In Man (see Fig. 31, p. 73) the presternum 
is broad and flat, hollowed in the middle line in front, and 
expanded laterally to give large surfaces for the attachment 
of the clavicles and the first pair of 
ribs. The mesosternum is elongated, 
but is also comparatively broad and 
flattened. It consists of four distinct 
segments. ‘The x7phisternum is a 
more or less elongated posterior ap- 
pendage, varying somewhat in form 
and size in different individuals. 

The ossification of the human 
sternum is ezdosteal, or Commencing 
within the substance of the primitive 
hyaline cartilage. The presternum 
Fic 32.—Sternum of young OSsifies from one, or sometimes two, 

Hien, pein centres, which may be placed side by 

ee side, or one in front of the other. 
Each of the segments of the mesosternum has a distinct 
centre, though these may be double in their earliest con- 
dition, and sometimes remain so for a long period. 

The segments of the mesosternum usually unite together 
sc as to form one continuous bony piece, to which the pre- 
sternum often remains throughout life connected only by 


Tt S$ 


vil. ] PRIMATES. 75 


fibrous tissue, although it is not unfrequently ankylosed in 
old age. 

The xiphisternum ossifies irregularly and imperfectly. 

The Gorilla, Chimpanzee, Orang, and Gibbons, resemble 
Man, and differ from the other monkeys in the breadth and 
flatness of the sternum. It is broadest in proportion to its 
length in the Siamang (/7/y/obates syndactylus). In the Orang 
(Fig. 32), each segment of the mesosternum is developed 
from a pair of lateral ossifications, 
which commonly remain separate until 
the animal is about half-grown.} 

In the lower Monkeys the pre- 
sternum is somewhat broad, but the 
bones constituting the mesosternum 
are elongated and compressed, and are 
not ankylosed together as in Man and 
the highest Apes. Their number varies 
from three to five. In the Howling 
Monkey (AZycetes) the presternum has 
in front of it two large diverging horns 
(pro-ostea, Parker), which ossify sepa- 
rately and support the clavicles and 
either the whole or part of the first 
pair of ribs. 

In the CaRNIVoRA, the sternum —- 
(Fig. 33) is generally composed of Fic. 33 —Sternum and sternal 
eight or nine pieces altogether, in- Hhovio) rar ae ae 
cluding the presternum and the xiphi- feat 
sternum. 

The presternum, or manubrium, is long and narrow, 
somewhat expanded near the front for the attachment of 


1 The sternum of a young Gorilla in the Museum of the College of 
Surgeons presents the same condition. 


76 THE STERNOA. [CHAP. 


the first pair of sternal ribs, and terminating anteriorly in a 
conical rounded projection. 

The segments of the mesosternum are elongated, and 
more or less four-sided, contracted at the middle, and 
widening at each extremity. They ossify, according to 
Parker, ectosteally, or from without inwards, the bony 
deposit commencing in the inner layer of the perichon- 
drium, as in the shafts of long bones; and they remain 
permanently distinct from each other. 

The xiphisternum is long, narrow, and flat, and generally 
ends in an expanded flattened cartilage.! 

In the Pinnipedia, the presternum is produced considerably 
in front, of the attachment of the first pair of ribs. 

In the INSECTIVORA, the sternum is variable in form, but 
always more or less elongated and segmented. ‘The pre- 
sternum is always more or less expanded laterally in this 
claviculated group of animals. It is bilobate in front in 
the Hedgehog (Z7znaceus), trilobate in the Shrews (Sorex). 
In AAynchocyon it is broad in front, narrow posteriorly, 
strongly keeled below, and with two horn-lke processes 
projecting outwards and forwards between the attachment 
of the clavicles and the first pair of ribs. 

The mesosternum is usually narrow, as in the Carnivora, 
but in the Hedgehog, where it consists of three segments, 
it is broad and flat posteriorly. In this genus the xiphi- 
sternum is rudimentary, whereas in the Shrews it is long 
and ends in a flat expanded cartilage. 

The Mole (Za/fa) and its nearest allies have a remarkably 
developed presternum, which is longer than the whole of the 
mesosternum (Fig. 34). It is strongly keeled below, except 
at the front part, which is much thickened. On its superior 
or inner surface it is grooved in the middle line. Laterally it 


1 This is not preserved in the specimen figured. 


vi] INSECTIVORA. 77 


gives off a pair of wing-like processes, behind which the first 
pair of ribs are attached. It is distinctly separated from the 
mesosternum, which consists of five segments of nearly equal 
width. The xiphisternum has a broad oval cartilaginous ex- 
pansion posteriorly, not shown in the figure, 
which is taken from a dried specimen. 

As the clavicle is supported at the 
anterior extremity of the elongated pre- 
sternum, it is widely separated from the 


first nb, and the anterior extremities are 
brought into such close juxtaposition with 
the head, that the animal appears to have 

no neck. 

In the CHIROPTERA, the sternum pre- 
sents a considerable general resemblance 4,<. Ames of 
to that of Man. ‘The presternum is large, pip: ar eee 
trilobate in front, and strongly keeled. Sinim: xs xiphi 
In many of the Insectivorous Bats the seg-  ¢trnm5.f pont of 
ments of the mesosternum are (at least in Vile 
adults) firmly ankylosed together, but in the frugivorous 
Bats (/veropus, &c.) they continue separated. 

- In the RopEnTI!A, the sternum is long and narrow, consist- 
ing of a presternum (which is generally broad in the forms 
which have the clavicle well developed, as the Rats, Beavers, 
&c.), a mesosternum of three, or more usually four, seg- 
ments, and a long xiphisternum, with a broad cartilaginous 
terminal expansion. The segments of the mesosternum 
often have epiphyses at each end. 

The presternum is compressed and produced forwards in 
those species in which the clavicle is absent or rudimentary, 
as the Aguti, the Hares, and the Capybara. In the latter 
it much resembles that of the Horse or Tapir. 
Order Uncutata.—In the Ruminantia there are usually 


“8 - THE STERNUM. [cHAP. 


seven segments altogether in the sternum (Fig. 35). The 
presternum is narrow, rounded in front, and bearing the 
first pair of sternal ribs close to its apex. The succeeding 
pieces gradually widen, the posterior segments of the meso- 
sternum being square, flat, and rather massive (especially in 


LS 


Fic. 35.—Sternum and sternal ribs of Fic. 36.—Sternum of the Pig (Sms 


the Red Deer (Cervus elaphus), +. ps scrofa), 4. ps presternum ; 7zs meso- 
presternum; 7s mesosternum; +s sternum ; xs xiphisternum. 
xiphisternum. 


the Giraffe); they are hollowed at the middle of their 
lateral borders. ‘The xiphisternum is thin and flat. 

In the Pig (Fig. 36) and Hippopotamus the presternum 
is compressed and keeled ; the articular facets for the first 


vit] UNGULATA. "9 


pair of ribs are close together on its upper surface ; but 
the mesosternum is broad and flat, the first segment being 
transitional, compressed in front, and broad posteriorly. The 
xiphisternum is narrow and pointed. The sternum of the 
Pig very often retains indications of the primordial median 
fissure through life. 

The Horse and the Tapir have a very peculiar sternum. 
The presternum is extremely compressed and projects forward 
like the prow of a boat. Jn the Tapir, its anterior portion 
is originally, and commonly remains, a distinct ossification 
(pro-osteon, Parker). The segments which follow gradually 
widen, and the hinder part of the sternum is broad and flat. 
The last mesosternal segnient in the Tapir is generally 
divided in the middle line, and is not followed by a 
xiphisternal element. 

The sternum of the Rhinoceros, on the other hand, is 
very narrow throughout, with a long, rather spatulate xiphi- 
sternum. 

Order CeTacEA.—Each of the two primary divisions of 
this order has a distinct form of sternum. 

Among the Odontocetz, the typical Dolphins have a very 
broad presternum of peculiar form, emarginate in the 
middle line in front, and with a pair of lateral processes 
behind the attachment of the first pair of nbs. This is 
followed by two or three mesosternal segments, but no 
xiphisternum. An indication of the primordial median 
fissure can generally be traced, except in very old animals, 
either as a hole in the presternum, or as a division of the 
posterior mesosternal segment. 

In the Porpoise (Phocena) the sternum is shorter and 
broader than in most Dolphins, and its various elements 
early coalesce into a single bone. 

In the Cachalot (Physeter ER the sternum 


So “" DHE STERNOA. [CHAP. 


ossifies from three distinct pairs of nuclei, and a large 
median fontinelle remains between the first and second 


Fic. 37.—Sternum of Cachalot or Sperm Whale (Physeter macrocephalus), 3. 


pair.! In the specimen in the Museum of the Royal College 
of Surgeons, which is very nearly adult, each half of the 


Fic. 38.—Sternum of Greenland Right Whale (Balena mysticetus), 5. 


presternum (fs) has coalesced with the corresponding 
half of the first segment of the mesosternum (s*), but the 


1 | have observed this in animals evidently of great age. 


Bri] CERTACEA, 81 


resulting pieces are not united by bone across the middle 
line, while the second or last pair of mesosternal segments 
(ms?) are ankylosed together mesially, but not with the 
portion of the sternum in front of them. 

In the Whalebone Whales (4% stacocet/) the sternum is 
comparatively rudimentary, consisting only of a broad, 
flattened presternum, produced posteriorly into a xiphoid 
process in some species. ‘There are never any mesosternal 
segments, and consequently no ribs, other than the first 
pair, are attached to it. 


Fic. 39.—Sternum of Common Rorqual or Fin Fic. 40.—Sternum of Pike Whale 
Whale (Salenoptera musculus), 5. (Balenoptera rostrata), x5. 


The presternum is ossified from one, or perhaps a pair of 
symmetrical nuclei. In the Right Whales (Bad/ena, Fig. 38) 
it is heart-shaped, or longitudinally oval. In the Fin Whales 
(Lalenoptera) it is transversely oval or trilobate, with a 
backward projecting xiphoid process.’ In young animals 


' In the cartilaginous sternum of a young Salenoptera sibbaldii 
Professor Turner found the xiphisternum to be quite distinct from the 
presternum, and connected with it by fibrous tissue. (Yournal of 
Anatomy, May 1870.) In most Whales the sternum shows no such 
evidence of segmentation. 


G 


82 THE STERNUM. (CHAP. 


ossification of the cartilaginous sternum advances forwards 
on each side of the middle line, so that the ossified portion 
at one period appears deeply notched in front ; as the bone 
meets across the middle line anteriorly, this notch usually 
becomes converted into a hole (see Fig. 39), which finally 
closes with complete maturity. 

In the Pike Whale (2. rostrata) the sternum is cross- 
shaped (Fig. 40), the first ribs being attached behind the 
iateral arms of the cross. 

In the StRENIA the sternum is a simple, flattened, some- 
what elongated bone, which in the adult shows no trace of 
segmentation. 


Fic. 41.—Sternum of a young Dugong (Hadicore indicus), 4. From a specimen in 
the Leyden Muiseum. 


In a young Dugong (Aalicore), Fig. 41, there are two 
distinct ossifications,—a presternum (fs), to which the first 
pair of ribs are attached, and a xiphisternum (xs). The 
second, third, and fourth pairs of sternal ribs are attached 
to the intermediate unossified portion, representing a rudi- 
mentary mesosternum. 


VII.] EDENTATA. 83 


In the Manati (AZanatus) the sternum is of somewhat 
similar form, and has three pairs of ribs attached to its 
lateral margins near the middle. 

Among the EpentTata there is considerable variation in 
the characters of the sternum. 

In the Cape Anteater (Orzycteropus) the sternum is of 
quite a normal form. The presternum is trefoil-shaped, 
expanding laterally near the front to meet the largely de- 
veloped clavicles, then contracting to the width of the 
mesosternal segments, which are four in number, simple, 
flattened, oblong, with lateral margins nearly. parallel, 
rather broader above than below, united together by fibrous 
tissue, and succeeded posteriorly by a moderately deve- 
loped xiphisternum. 

In Manis dalmannii the sternum is flat, consisting of 
seven segments, several of which are sometimes divided 
in the middle line by synovial cavities. The xiphisternum 
is very long, partially cleft in the middle line, and ending 
in a large, flattened, cartilaginous expansion. In the Long- 
tailed Pangolin (A/anzs longicauda) the xiphisternum is of a 
remarkable form, being prolonged into a pair of cartila- 
ginous processes, each about nine inches long. and con- 
nected posteriorly with some rudimentary abdominal ribs.’ 

In the Anteaters (AZyrmecophaga) the presternum is broad, 
flat, and oval. The segments of the mesosternum (Fig. 42) 
are eight in number, short, deep, broad above, and sending 
a club-shaped process downwards; each is ossified from a 
principal endosteal centre and eight epiphyses, is connected 
by synovial articulations with the segment before and behind, 
and has at either end an upper and lower hollowed surface, 
which, with the corresponding surfaces on the contiguous 
segment, form articulating facets for the double-headed 

1 Parker, of. cit. 
G2 


84 THE STERNOM. [CHAP.° 


sternal ribs. This mode of articulation curiously resembles 
that at the vertebral end of the rib. The xiphisternum is 
rather long and simple. 

In the small Tree Anteater (Cyclothurus didactylus) the 
presternum is very broad and trilobate, sending out lateral 
expansions behind the attachment of the clavicles to meet 
the first pair of ribs. ‘The hinder, narrow part of the manu- 
brium is segmented off from the larger anterior part, and 


Fic. 42 —Side view of three mesosternal segments from a young Anteater (J/yraze- 
cophaga tamandua), showing the mode of articulation of the sternal nb (s7, 
copied from Parker’s figure. #zs¢ the upper or inner surface of the mesosternal 
segment ; sy the synovial articulation between the segments. 


resembles a mesosternal segment ; but it 1s in front of the 
attachment of the second pair of ribs. The true mesosternal 
segments are six in number, of nearly equal width, high, 
rounded above, and compressed below, with a synovial 
cavity between each. ‘The sternal ribs are articulated by a 
single oval condyle. The xiphisternum is long, stout, and 
styliform. 

In the Armadillos (Dasypodide) the presternum is broad, 
and in Priodontes gigas (Fig. 44, p. 95) strongly keeled. The 
mesosternal segments, four to six in number, are broad above, 


vit] EDENTATA. 85 


but very narrow below ; and, according to Prof. Parker, each 
ossifies from eleven centres. They are connected by syn- 
ovial joints to each other, and to the strongly ossified sternal 
ribs, which have broad, sub-bifid heads. The xiphisternum 
expands posteriorly into a wide cartilaginous flap. 

In the Sloths the sternum is long and narrow. The Three- 
toed species (4radypus) have a rather broad presternum, but 
with no prolongation in front of the attachment of the first 


Fic: 43.—Sternum and adjacent parts of the skeleton cf a young Ornithorhynchus 
(O. paradoxus). c clavicle; zc interclavicle, fo pro-osteon (a part of the true 
sternum) ; fs presternum ; #zs mesosternum; sv sternal ribs ; 77 intermediate ribs ; 
wry vertebral ribs. 


rib. This is followed by eight small mesosternal segments, 
and a very small rounded ‘xiphisternum. In the ‘Two-toed 
Sloths (Cho/epus), the presternum is narrow, slightly keeled, 
and forms a considerable projection in front of the attach- 
ment of the first rib. The mesosternum has twelve seg- 
ments, and the xiphisternum is rudimentary or absent. 


86 THE STERNUM. [CHAP. VII. 


In the MarsupPIALia the sternum presents no especial 
aberrant characteristics. The presternum is rather broad at 
the point of attachment of the first pair of nbs. Its anterior 
extremity often does not ossify. ‘There are usually four 
quite distinct, elongated segments to the mesosternum, 
connected to one another by fibrous tissue, and sometimes 
completed at each end by epiphyses. ‘The xiphisternum 
has an elongated, narrow, ossified portion, and terminates 
in a laterally expanded cartilage, which may contain one 
or two endosteal bony patches. 

In the MonoTREMATA the Orithorhynchus (Fig. 43) has 
a broad presternum (fs), with a small partially ossified 
pro-osteon (fo) in front of it; three keeled mesosternal 
segments (ms), which commence to ossify in pairs, and 
no xiphisternum. ‘The Echidna agrees in all important 
respects, but it has an ossified xiphisternum. 

The T-shaped bone, éz¢erclavicle or episternum (ic) in front 
of the presternum, which connects it with the clavicle, and 
which appears to have no homologue among the other 
Mammalia, belongs more properly to the shoulder-girdle 
than to the sternal apparatus. 


CHAPTER, VEIT. 


THE RIBS. 


THE nbs form a series of long, narrow, and more or less 
flattened bones, extending laterally from the sides of the 
vertebral column, curving downwards towards the median 
line of the body below, and mostly joining the sides of the 
sternum. 

Free ribs are normally only attached to the thoracic ver- 
tebrze, although, as before shown, certain parts, which may 
be serially homologous with ribs, are found in other regions 
of the vertebral column ; but in such cases they become 
ankylosed with their corresponding vertebre. In the 
thoracic region, the ribs are never normally ankylosed 
with the vertebrze, but are articulated to them by synovial 
joints, which permit a certain, though limited, amount of 
motion. 

As a general rule, the first thoracic rib joins the pre- 
sternum or manubrium ; sometimes, as in the Whalebone 
Whales, this is the only rib united below to the sternum, but 
usually a larger number are so connected, while the more 
posterior are either attached by their extremities to the 
edges of the ribs in front of them, and thus indirectly join 
the sternum, or else they are quite free below, meeting no 
part of the skeleton. ‘These differences have given rise to 


88 SHE RIS. [CHAP. 


the division into ¢zrwe ribs and fadse ribs (by no means good 
expressions), signifying those that join the sternum directly 
and those that do not; and of the latter, those that are 
free below are called flvating ribs. 

Each primary piece of cartilage, out of which one of the 
half hoops or ribs is developed, is, moreover, divided trans- 
versely into two portions, which assume different characters, 
as they usually undergo a different mode of ossification, and 
remain more or less distinguishable from each other during 
life. The portion nearest the vertebral column is called 
the vertebral rib. This is the larger segment, and becomes 
firmly ossified at an early period by ectostosts,;* it is the 
bone commonly spoken of as a “rib.” 

The portion towards the sternal extremity or sterna/ rib 
is usually imperfectly ossified, and always at first (except 
in Monotremes) by evdosfosis.2, Sometimes it remains per- 
manently in a cartilaginous state ; but, on the other hand, in 
some cases it becomes as firmly ossified as the vertebral 
ribs. 

The vertebral ribs are variously connected with the 
sternal ; by continuous cartilage ; by intercalation of fibrous 
tracts ; or by synovial joints. 

Occasionally, in the Mammalia, an “intermediate” 
. portion of the rib is segmented off, as in Reptiles ; this is 
best developed in the Monotremata (Fig. 43, 27), where, 
however, it is only partially ossified by ezdostosis. In all 
other instances in which it occurs it is quite rudimentary. 

The vertebral ribs, when in their most typical condition, 
have two points of attachment to the vertebra ; the tubercle 


P 
1 The bony deposit commencing at the surface, and advancing in- 
wards, as in ordinary long bones. 
* The bony deposit being irregularly scattered throughout the carti- 
lage, often beginning near its central part. 


Vl. | GENERALE CHARACTERS. 89 


(¢uberculum) and the head (capitiulum). The former is 
superior and posterior, and attached to the transverse pro- 
cess of the vertebra; the latter, inferior and anterior, and 
attached to the body of the vertebra, or the inferior part of 
the arch near the body, and always very near the neuro- 
central suture. Commonly, in fact, the articular surface is 
cut by this suture. Sometimes, as in Man, the greater part 
of the articulation is above the suture; or, on the other 
hand, it may be, as in the AZonotremes, below the suture. 
The distinction between the two points of attachment is 
most marked in the anterior ribs ; in passing backwards 
they approach nearer to each other, sometimes becoming 
blended, or sometimes either one or the other (generally 
the tubercular) attachment is lost in the hindermost ribs. 

The tubercle articulates, by a nearly flat or slightly con- 
vex surface, to a facet on the under-surface of the extremity 
of the transverse process of the corresponding vertebra, but 
the more rounded capitulum (at least in the anterior nbs) is 
placed opposite to the intervertebral space in front of this 
vertebra, and portions of two vertebraee commonly contribute 
to form the articular cavity for its reception. Thus the first 
rib 1s articulated by its tubercle to the transverse process of 
the first thoracic vertebra, and by its head to the hinder 
part of the seventh cervical, and front part of the first 
thoracic vertebra, and so on. ‘The posterior ribs, as a rule, 
are connected solely with their own corresponding ver- 
tebre. 

The amount of motion permitted by these articulations 
is sufficient to allow the thorax to expand and contract in 
respiration. In inspiration the ribs are drawn forwards, and 
approach nearer to a right angle with the vertebral column ; 
while in expiration they fall back, and occupy a more 
oblique position to the axis of the column. 


” 
GO THE RIBS, [CHAP. 


The sternal ribs are connected with the sternum either by 
interposed fibrous tissue, or by distinct synovial joints. The 
first is attached to the side of the presternum, the second 
Opposite to the junction of the presternum and the first 
mesosternal segment, and the succeeding ones opposite to 
the interspaces between the other mesosternal segments ; 
though two or more may be attached to the hinder end of 
the last of these segments. The inferior ends of the so- 
called “false ribs” are attached by fibrous tissue, or by 
synovial joints, to the hinder borders of the sternal ribs in 
front; though, as before said, the most posterior are free or 
‘* floating.” 

The ribs of Mammals never have “ uncinate processes,” 
like those found in Birds and Reptiles. 

The most prevalent number is thirteen pairs; the lowest 
is nine (in yperoodon), the highest twenty-four (in the Two- 
toed Sloth, Cholepus. 

Special Characters of the Ribs in the various Groups of 
Mammalia. Order Primates.—In Man there are nor- 
mally twelve pairs of nbs, of which the first seven are 
reckoned as true ribs, and the last two as floating nbs. 
The last pair may be rudimentary or absent; or, on 
the other hand, the seventh cervical or the first lumbar 
vertebra may have an additional movable rib articulated 
with it. 

The first vertebral rib is much shorter, broader, flatter, 
and more curved than the others. ‘These gradually increase 
in length until the seventh, after which they again diminish 
to the twelfth. In breadth they gradually decrease from 
the first to the last. 

The portion of the rib between the head and the tubercle 
is called the meck, it is wanting in the last two ribs, in 
which the two attachments are blended. The greatest point 


a] 


VIII. ] PRIMATES. 91 


of curvature on the external surface of the rib is called the 
angle. 

Each vertebral rib has a main centre of ossification and 
two epiphyses, one for the head, and (except in the last 
two), one for the tubercle. 

The sternal ribs generally remain cartilaginous throughout 
life, being only partially ossified by endostosis in old age 
or under abnormal conditions. They are not distinctly 
separated from the vertebral ribs except by their difference 
of structure; but synovial joints are (except in the first) 
interposed between their inferior extremities and the 
sternum. | 

Among the higher Szmzznza the nbs do not differ very 
notably from those of Man, except in number ; but in the 
lower forms, and especially in the Lemuzsina, they more 
resemble those of the Carnivora. Among the Old World 
Monkeys, the number varies from 11 to 13 pairs. The 
Gorilla and Chimpanzee (7Zvoglodytes) have 13, and the 
Orang (S‘mza) 12. In the American Monkeys there are 
from 12 to 15 pairs; in the Lemurs from 12 to 16 pairs. 

In the most typical forms of Carnivora, the vertebral 
ribs are comparatively slender, subcylindrical, and little 
curved. The most anterior especially are short and straight, 
the thorax being thus more compressed in front than it is in 
Man and the higher Primates. The sternal ribs (see Fig. 
33, p. 75), are long, slender, have a feeble granular ossifica- 
tion, and are not otherwise segmented off from the vertebral 
ribs. In all the Fedéde and Canidae there are 13 pairs, in 
the Viverride 13 or 14, in the Hyenide 14 or 15, in the 
Mustelide 14 to 16, in the Procyonide 14, in the Urside 14 
or 15, In the Prnnzpedia 14 oF 15. 

In the Uncutata, the ribs are generally more or less 
flattened and broad, notably so in the Ox and Camel, and 


92 HH ET RIBS. [CHAP. 


least so in the erzssodactyla. The anterior ribs have 
scarcely any curve, the thorax being very narrow in this 
region. ‘The sternal ribs (see Fig. 35, p. 78), especially 
those near the front of the series, are short, stout, rather 
flattened or prismatic, tolerabiy well ossified, and articulated 
with the vertebral ribs by a cup-and-ball synovial joint. 
The Artiodactyles have from 12 to 15 pairs of ribs, the 
Horse and Tapir 18, the Rhinoceros 19, the Elephant 19 
or 20, and the Hyrax 20 to 22. 

In the Srrenra, the total number of ribs Is very great, 
though but few are attached to the sternum. In the 
Manati they acquire an extraordinary thickness and so- 
lidity of texture. This animal has seventeen pairs, of 
which but three are attachéd by flexible cartilages to the 
sternum. ; 

Order Ceracea.—In the Whalebone Whales the ribs differ 
greatly from those of the rest of the Mammalia in their ex- 
tremely loose connection, both with the vertebral column 
above and with the sternum below, probably to allow of 
greater alteration in the capacity of the thorax in respiration, 
necessitated by the prolonged immersion beneath the sur- 
face of the water which these animals undergo. 

At their vertebral extremities they are attached only by 
their tubercle to near the end of the transverse process, but 
apparently not by synovial articulation. The heads of only 
a few of the anterior ribs are developed, and are rarely suf- 
ficiently long to reach the bodies of the vertebree, their 
place being supplied by a hgamentous band. The first rib 
is the only one connected with the sternum, either directly 
or indirectly, the whole of the remainder being free or 
floating ribs. The sternal ribs are mere cartilaginous rudi- 
ments, connected by an intermediate layer of fibrous tissue 
to the inferior extremity of the vertebral rib; at least such 


VALET | CETACEA., 93 


is their condition in the foetus of Ralena mysticetus, as 
described by Eschricht and Reinhardt. 

Balenoptera rostrata, the smallest of the Whalebone 
Whales, has but 11 pairs of ribs, Alegaptera longimana 14 
pairs, the Greenland Right Whale (Lalena mysticetus) 
usually 13, and. the larger Fin Whales (Balenoptera musculus 
and stbbaldiz) 15, and occasionally 16, the highest number 
known im any Cetacean. In these last, it not unfrequently 
happens that the hindermost rib, having only the middle 
or lower portion developed, is separated by a wide interval 
from the vertebral column, a very rare condition, as in most 
other cases where the hinder ribs are rudimentary the part 
in immediate connection with the vertebra remains. 

The first nb presents a very anomalous condition in some 
Whalebone Whales, being apparently double, probably owing 
to the coalescence of a supplemental cervical rib with the 
ordinary first thoracic nib. In some species (as Balenoptera 
daticeps) this appears to be of constant occurrence ; in others, 
it is occasional.’ 

In the Odontocetz or Toothed-whales, as the common Dol- 
phin and Porpoise, the ribs (usually t2 or 13 pairs) are long 
and slender. ‘The first four or five have tubercles, by which 
they articulate with the transverse process of the thoracic 
vertebrae, and long necks and heads, reaching to the side of 
the antecedent vertebra, near the junction of the body and 
the arch (see Fig. 20, p. 53). The posterior ribs, however, 
lose the neck, and are solely articulated by the tubercle to 
the transverse process. There are usually 7 pairs of rather 
short, straight, but strongly ossified sternal ribs, and often 
small intermediate ribs, sometimes distinctly ossified. 

In the aberrant Physeteride, including the Sperm Whale, 


e See Professor Turner “f On the so-called Two-headed Ribs in Whales 
and in Man.” (Journal of Anatomy and Physiology, May 1871.) 


94 LAE RIBS. [CHAP. 


Hyperoodon and various forms of Ziphioids, the ribs are 
connected to the vertebree throughout the greater part of the 
series by both head and tubercle; but a few of the most 
posterior have only a single point of attachment in con- 
sequence of the changes which take place in the condition 
of the transverse processes of the vertebra, described at 
p. 53. In this family the sternal nibs are either permanently 
cartilaginous, or very imperfectly ossified. The Hyperoodon 
has but 9 pairs of vertebral ribs, the smallest number 
known in any Mammal, the Sperm Whale (Physeter) 11, 
of which the last is quite rudimentary ;»ZzfAzws 10, and 
Kogia 14. 

Among the Epentata, the Sloths have very numerous 
ribs (from 15 to 24 pairs). In the anterior part of the thorax 
the sternal ribs are firmly ossified, and indistinguishable 
from the vertebral ribs (at least in adult age), but posteriorly 
they are separated from the latter by a less perfectly ossified 
intermediate rib. 

In the Armadillos the nbs are comparatively few (ro to: 
12 pairs), and are broad and flat, the first extremely so. The 
first sternal rib is very short and incorporated with the ver- 
tebral rib, but the others are very strongly ossified, and 
articulated by synovial joints with the sternum, with each 
other, and with the vertebral ribs. 

The peculiar double articulation of the sternal ribs with 
the sternum in the Anteater (4Zyrmecophaga) has been already 
described (see p. 83). The ribs of the small climbing Two- 
toed Anteater (Cyclothurus didactylus) are remarkable for a 
thin lamelliform expansion of their hinder border, over- 
lapping the succeeding rib. ‘This animal has 15 pairs, the 
great Anteater 16, the Cape Anteater (Orycteropus) 13. 

The MarsupiAia have nearly always 13 pairs of ribs ; 
the Koala (Phascolarctos) with but 11, and the common 


VIII. | MWARSUPIALTA. 95 


Wombat (Phascolomys vombatus) with 15, being the only 
known exceptions. The sternal mbs are articulated by 
synovial joints with the sternum, but are not distinctly 
segmented from the vertebral ribs, and are but feebly 
ossitied by endostosis. There are no intermediate ribs. 


Fic. 44 —Sternum and ribs of the Great Armadillo (Priodontes gigas), }. 
Ps presternum; rs xiphisternum. 


In the MonoTrreMaTa the intermediate ribs are well 
marked (see Fig. 43, p. 85), and only partly ossified by 
endostosis, while the sternal ribs (except the first) are, 
according to Parker, strongly ossified ectosteally, as in Birds. 
The hinder sternal ribs are very broad and flat. The 
Echidna has 16, and the Ornithorhynchus 17 pairs of 
vertebral ribs; they do not divide above into head and 
tubercle, but are attached only to the sides of the bodies 
of the vertebree. 


CHAPTER AX. 
THE SKULL. 


Tue skull is the term commonly applied to the expanded an- 
terior portion of the axial skeleton situated within the head. 

It consists mainly of the cranium, a strong bony case or 
frame, enclosing the brain, and affording support and pro- 
tection to the organs of smell, sight, hearing, and taste, 
and formed by the close union, either by sutures or by 
synostosis, of numerous bones. 

To the inferior surface of the cranium are suspended 
(1) the ALandible, or lower jaw, movably articulated by a 
synovial joint; and (2) a group of skeletal structures called 
the hyowdean apparatus. 

The diagram at p. 106 is intended to show, at a single 
view, the names applied to the various bones,of which the 
skull is composed, and to give some idea of their relative 
position. 

It will be well to commence the study of the skull by 
describing that of a Dog, as a good average specimen of the 
class, and one which is easily procurable at various ages ; 
and I would strongly advise the student to follow the 
description with a skull in his hand, or two would be better, 
in one of which a longitudinal median section has been 
made. In the other, the various bones should be separated 


CuAP. 1X. | THE SKOBL OF ‘THE DOG. Ge 


from each other. For this purpose a young animal, still 
retaining the milk teeth, will be best.t 
The skull has a longitudinal central axis (the cranio-facial 


Pr Pa LO P- 
CH 


ME \ tA te 


\ Z 


\ 
\ AXE 
: ae 
Sea J J 


\ 
\ 


Na 
YI Me 
mY \ 
\ rn 


#FxO 


— 
SS 
SS 


Fic. 45.—Longitudinal and vertical section of the skull of a Dog (Cazis familiaris), 
with mandible and hyoid arch, 3. az anterior narial aperture; 477 maxillo- 
turbinal bone; #7 ethmo-turbinal; Wa nasal; JZE ossified portion of the 
mesethmoid ; C£ cribriform plate of the ethmo-turbinal; #7 frontal; Pea parietal : 
/P interparietal ; SO supraoccipital; #2O exoccipital; BO basioccipital ; Per 
periotic ; BS basisphenoid ; Pf pteryg-id; AS alisphenoid ; OS orbitosphenoid ; 
PS presphenoid; P/ palatine; Vo vomer; JZ% maxilla; Pd/x premaxilla ; 
sh stylohyal ;.e% epihyal; ch ceratohyal ; 64 basihyal; ¢# thyrohyal ; s symphysis 
of mandible ; cf coronoid process: ca condyle; @ angle; zd inferior dental canal ; 
the mandible is displaced downwards to show its entire form ; the * indicates the 
part of the cranium to which the condyle is articulated. 


axis, Huxley) around which all its parts are arranged, and 
its structure will be best understood by commencing with 
the description of the bones forming this axis. 


1 When the zoologist wishes to throw into the strongest relief the 
distinctive characters of different species, he selects for comparison fully 
adult examples ; when the anatomist wishes to trace their community of 
structure and their resemblances, younger specimens are better adapted 
for his purpose. 

H 


98 LAE SKULL [ CHAP. 


When the skull remains in connection with the vertebral 
column, it will be seen that its axis is a continuation for- 
wards of the axis of that column, consisting of the bodies of 
the vertebree ; and that its hinder termination is placed in 
the same line with the odontoid process of the second cer- 
vical vertebra, the anterior termination of the axis of the 
spinal column. 

The large cavity above the axis of the skull (cerebral 
cavity) is in direct continuity with the spinal canal above 
the axis of the vertebral column. 

Beginning at the posterior end of the axis, the section 
will be seen to have passed through a flat, elongated bone 
(Fig. 45, BO), terminating freely behind at the inferior 
margin of the great opening (foramen magnum) at the hinder 
end of the cerebral cavity, by which this cavity is continued 
into the vertebral canal, and through which the backward 
prolongation of the brain (the medulla spinalis) passes. This 
bone is the daszoccipital. 

Immediately in front of this is a bone (the daszsphenoid, 
BS) not quite so elongated from before backwards, but of 
greater vertical depth; the interior being more or less 
cellular in structure. The under surface is flat, but the 
upper surface is hollowed in the middle, and raised at each 
extremity. This hollow corresponds to the part called 
“‘ sella turcica” in the human skull, and lodges the pituitary 
body of the brain. 

Further forwards, and likewise separated by a vertical 
fissure, is a bone (7S) of about the same length as the last, 
but still more elevated, and very cellular within. Its in- 
ferior contour is perfectly straight, but above it is somewhat 
irregular. This is the presphenoid. | 

So far the cranio-facial axis consists of bones. placed in 
2 continuous line, more or less depressed, and broad from 


1x. -OMTHE DOG. :, 99 


side to side, and forming the floor of the cranial cavity ; 
but the continuation of the axis forward is of a different 
character. The anterior end of the presphenoid ndrrows 
considerably, and the segment in front of it, in very young 
skulls, is a much compressed vertical plate of cartilage, of 
very considerable size, both from before backwards and 
from above downwards. Ossification of this cartilage com- 
mences in the posterior end and upper part, and spreads 
forwards and downwards, but it never or very rarely reaches 
its anterior extremity ; and in the animal now described a 
narrow inferior margin remains permanently cartilaginous. 
The ossified portion of this cartilage (47) constitutes the 
lamina perpendicularis of the ethmoid bone, the anterior 
unossified portion the septal cartilage of the nose, which is 
the anterior termination of the cranio-facial axis. The 
term mesethmoid may be applied to the whole of this element 
of the skull, whether ossified or not. 

Above all the posterior, or dasicranial, part of this axis, 
constituted by the three first-mentioned bones, is the cere- 
bral cavity, the walls of which constitute the “ brain-case.” 

These walls are formed by several more or less expanded 
and curved bones, which rise up from the sides of the axis 
or floor of the cavity below, and, meeting in the middle line, 
roof in the cavity above. These bones are arranged in 
three sets from behind forwards, each corresponding with 
one of the axial bones, and with the latter constituting one 
of the three segments or bony rings into which the brain- 
case may be divided. 

The hindermost (or occipital) segment consists of the 
basioccipital below; next on each side the exoccipitals (ZO), 
and a large, median, flat bone above, with its upper ex- 
tremity prolonged forwards in the middle line between the 
bones of the next segment, called the supracccipital ($Q). 

H 2 


100 TH SOLE [CHAP. 


These four bones surround the foramen magnum behind, and 
all take share in its circumference, though the exoccipitals, 
which bound it lateraily, contribute most. On each side of 
the foramen, and rather below than above, are the occipital 
condyles, by which the skull articulates with the first cervical 
vertebra ; and externally to these, separated by a deep de- 
pression, is a prominent process for muscular attachments, 
called the Aaroccipital (or paramastoid) process. The con- 
dyles in the Dog are formed by the exoccipitals alone. The 
part (7P) which appears to be an anterior prolongation of 
the upper extremity of the supraoccipital, wedged in be- 
tween the parietals, is ossified from a separate centre, and 
in some animals remains permanently as a distinct bone. It 
is then called ¢xterparietal. 

The middle (or parietal) segment is formed by the 
basisphenoid below. From the sides of this a pair of 
wing-like bones (4.S) extend outwards and upwards, 
called alisphenotds; and above these are large square- 
shaped bones (7a), meeting in the middle line above, the 
 parietals. 

The occipital and the parietal segments are in contact 
below and above, but there would be a considerable open 
space between. them laterally were it not for the inter- 
position of a group of bones, which do not form part of the 
segmented wall of the brain-case proper, but are more or 
Jess connected with the organ of hearing, and will therefore 
be described hereafter. ‘These are the bones which, being 
all united into one in Man, constitute the so-called ¢emporal 
bone of human anatomy. 

The anterior (or frontal) segment is formed by the pre- 
sphenoid below; then by the wing-like bones (OS) projecting 
from its sides, smaller than those of the second segment, 
called orbitosphenoids; and finally by two greatly expanded 


xe] OF THE DOG. IOI 


bones (/7), curving inwards above and in front, to close in 
the cerebral cavity in these directions, by meeting in the 
middle line. These are the fromfal bones. 

Between the middle bones of the parietal and frontal 
segments (alisphenoid and orbitosphenoid) is an iregular 
vacuity, called the foramen lacerum anterius, or sphenoidal 
fissure, through which several nerves pass to the orbit. This 
is the second vacuity in the side wall of the skull, the first 
being the one between the occipital and parietal segment, 
partially filled by the periotic bone. 

As the occipital segment is not closed behind, so in the 
same way the frontal segment is open in front, the aperture 
being bounded by all the bones which enter into its com- 
position—presphenoid, orbitosphenoids, and frontals. The 
hinder edge of the mesethmoid rising up to meet the 
frontals makes a median partition to this aperture (the crzs/a 
galli of human anatomy), and it is further closed by a 
special ossification (CZ) connected with the organ of smell, 
the cribriform plate. 

Thus the brain-case may be described as a tube, dilated 
in the middle, composed of three bony mngs or segments, 
with an aperture at each end, and a fissure or space at the 
sides between each of the segments. 

The cranial cavity thus formed is of a general oval form, 
but broader behind than in front. The floor is compara- 
tively straight ; the upper surface arched. It is imperfectly 
divided by bony ridges into three compartments. The 
most posterior of these, marked off in front by. a sharp 
ridge along the periotic bone (/e7), extending from near the 
junction of the basisphenoid and _ basioccipital, upwards, 
outwards, and backwards, along the line of junction of 
the parietal and supraoccipital, and strongly marked by an 
inward shelf-like projection from the former (the ossitied 


102 THE SICOLL [CHAP. 


tentorium cerevelli), 1s called the cerebellar fossa, as it 
lodges that division of the brain. The most anterior and 
smallest compartment is marked off by a vertical ridge on 
the orbitosphenoid and the frontal. Its walls are chiefly 
formed by the cribriform plate. This is the olfactory fossa 
(rhinencephalic fossa, Owen), for the lodgment of the olfac- 
tory lobe. Between these two is the great cerebral fossa, in 
which the hemisphere of the cerebrum hes. This is very 
imperfectly divided below into two compartments, by a slight 
ridge at the hinder edge of the orbitosphenoid and con- 
tinued thence outwards at the junction of the frontal and 
alisphenoid. ‘This ridge corresponds with the Sylvian fissure 
of the brain ; the part of the cerebral fossa in front of it 
lodges the frontal lobe of the cerebrum, that behind it the 
temporal lobe. 

Through the lateral parts of the floor of the cranial cavity 
are various perforations, or foramina, either holes passing 
directly through the bones, or vacuities occasioned by want 
of contact, for a limited space, of contiguous bones. These 
are mainly for the purpose of allowing of the exit of the 
various nerves which take origin from the brain; and as 
they are extremely constant in their position, and offer useful 
landmarks for determining the homologies of the bones 
throughout the vertebrate series, it 1s important that they 
should be well known. (See Diagram at p. 106.) 

1. The most anterior is the space, before spoken of, in 
front of the anterior segment, occupied by the hinder part 
of the ethmoturbinal, commonly called the ‘ cribriform 
plate.” The numerous perforations in this plate transmit 
the olfactory nerves arising from the olfactory lobes. 

2. Near the hinder border of the orbitosphenoid is a con- 
spicuous, nearly round, hole, through which the optic nerve 
passes, and hence called optic foramen. 


re OFTHE: DOG. 103 


3. At a very short distance behind this is a more irregular 
oval opening, between the orbitosphenoid and the ali- 
sphenoid. ‘This is the sphenoidal or orbital fissure, or 
foramen lacerum anterius. It leads into the orbit, and 
allows the exit of the motor nerves ‘of the eyeball, or third, 
fourth, and sixth cranial nerves, and also the third division 
of the trigeminal or fifth nerve. 

4 and 5. The alisphenoid near its base is perforated by 
two foramina; the anterior small and somewhat round ; the 
posterior larger and oval: these are the foramen rotundum 
and the foramen ovale, and transmit respectively the second 
and third divisions of the fifth nerve. 

6. Between the alisphenoid and the exoccipital is a large 
space, almost entirely filled by the bony capsule of the organ 
of hearing, the ferzotéc. In front of the inner end of this 
bone is an opening (foramen lacerum medium basts cranit), 
through which the internal carotid artery sometimes enters 
the cranial cavity. 

7. Near the middle of the inner surface of the periotic 
is the meatus auditortus titernus, ito which the seventh 
and eighth nerves enter: the former (the facial nerve) 
passes through the bone and emerges on the other side 
(by the stylo-mastoid foramen); the latter, the auditory, is 
distributed to the internal organ of hearing within the 
periotic bone. 

A deep depression seen above the internal auditory 
meatus, and of nearly the same size, is not a foramen but a 
fossa, lying within the concavity of the superior semicircular 
canal. It lodges the flocculus, a small process of the cere- 
bellum. 

8. Between the periotic and the exoccipital an irregular 
space is left (the foramem lacerum posterius), through which 
the glossopharyngeal, pneumogastric, and spinal accessory 


104 THE SKULE [CHAP. 


nerves (the ninth, terth, and eleventh) -pass out of the 
cranium. 

g. The exoccipital is perforated, a little in front of the 
condyle, by the condylar foramen, which gives exit to the 
twelfth, or hypoglossal, nerve. 

10. Lastly, the large median opening, behind the bones 
of the posterior segment of the skull, is the foramen magnum, 
through which the spinal cord passes out. 

It will be seen from the foregoing description that the 
three organs of special sense, situated in the walls of the 
cranium, have definite relations with the three osseous 
segments. ‘The first, or organ of smell, is situated in front 
of the frontal segment; the second, or organ of sight, 
receives its nerves by apertures situated between the frontal 
and parietal segments or perforating the former ; the third, 
or organ of hearing, is intercalated between the parietal 
and occipital segment. 


The portion of the skull anterior to the junction of the 
presphenoid and the mesethmoid constitutes the face. This 
differs entirely from the cranial cavity in having a complete 
median partition, and consists mainly of two tubular cavities 
placed one on each side of this partition. ‘These are the 
nasal cavities. They are open at each end, the orifices 
being termed respectively anterior and posterior nares. 

Each of these elongated cavities is deepest vertically in 
its posterior part, where it is partially divided into an upper 
and lower chamber: the upper one, the olfactory chambe;, 
being closed behind by-the cribriform plate ; the lower, the 
narial passage, terminating in the posterior nares. 

Each nasal cavity may be described as having an inner 
wall, an outer wall, a floor, and a roof. 

The inner wall is formed mainly by the partially ossified 


1X] OF CITE DOG . —- 105 


mesethmoid cartilage (AZZ), but the lower part of the pos- 
terior two-thirds also by the vomer (Vo). The greater part 
of this bone has the form of a trough, hollow above, em- 
bracing tne inferior, thickened border of the mesethmoid 
cartilage, and extending a little way behind this so as also 
to underlie the anterior portion of the presphenoid ; but it 
also develops from its under surface in the middle line a 
thin plate, which passes vertically down to the centre of 
the floor of the nasal passages, and completes the septum 
inferiorly. 

Above, rather behind the middle of the bene, the lateral 
plates of the vomer, which embrace the mesethmoid carti- 
lage, send out sideways a pair of wing-like processes, which. 
join the side walls of the nasal cavity, and form the partial 
horizontal partition, dividing the narial passage from the 
olfactory chamber. 

The outer wall of the nasal cavity is formed mainly by 
four bones: (1) a somewhat quadrate, thin, nearly vertical 
plate of bone (/7%), the Atervgord, attached above to the under 
surface of the basisphenoid and presphenoid, supported 
externally by a strong descending process of the alisphe- 
noid, the external pterygoid plate, ending posteriorly and 
inferiorly by a free border, and articulating in front with (2) 
the palatine. This bone (77) is of much greater extent ; for, 
besides its vertical portion, forming the outer wall of the 
nasal canal in front of the pterygoid, it sends from its upper 
edge a lamina inwards to meet the horizontal plate of the 
vomer, and aid in forming the root of the hinder part of the 
narlal passage. It also sends a strong horizontal lamina 
inwards from its, lower edge, which, meeting its fellow in the 
middle line, forms the posterior part of the floor of the narial 
passage. In addition to these it sends a broad plate upwards 


and forwards in the inner wall of the orbit. 
[Continued on p. 108. 


pg ea. aU 


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108 EGS eS G8 iss [CHAP. 


3. In front of this is the max://a (Mx), a still more con- 
siderable bone. It not only forms the chief part of the outer 
wall of the nasal cavity, but it also sends inwards a hort 
zontal plate, forming the middle part of its floor. At the 
junction of its vertical and horizontal portions is the alveolar 
border, in which the canine, premolar, and molar teeth are 
lodged. 

4. The most anterior bone of this series is the premaxzlla 
(PMx), which also has an ascending or vertical plate, 
forming the outer wall of the nasal cavity, and a horizontal 
plate forming the anterior part of its floor; at their junc- 
tion its alveolar border lodges the incisor teeth. The pre- 
maxilla forms the outer and lower boundary of the anterior 
nares. 

Besides these four, there is a small bone which enters into 
the outer wall of the upper part of the nasal cavity, between 
the ascending process of the palatine, the maxilla and the 
frontal. ‘This is perforated by the duct, which conveys the 
tears from the orbit into the nasal cavity, and is hence 
called Zachrymad. 

Above this a process from the frontal completes the 
upper and posterior part of the outer wall of the olfactory 
chamber. 

The floor of the nasal cavity is formed, as above said, by 
the horizontal plates of the palatine, maxilla, and premaxilla 
meeting the corresponding bones of the opposite side in the 
middle line. ‘The inferior surface of this same horizontal 
layer of bone is the roof of the mouth, or bony palate. 

The roof of the nasal cavity is formed posteriorly by 
the continuation of the frontal forwards beyond the cere- 
bral cavity, the “ zasal process of the frontal,’ but mainly 
by a long narrow bone, the zasa/ bone (Va). The hinder 
extremity of this lies upon the nasal process of the frontal ; 


IX.] OF THTE DOG. ; 109 


its anterior end is free, and forms the upper boundary of 
the anterior nares; its outer side is in contact with the 
frontal, maxilla, and premaxilla ; and its straight inner edge 
lies against that of the corresponding bone of the opposite 
sicle. 

Within each nasal cavity are two very singular bones, 
each being composed of a number of delicate lamellz 
folded and arranged in an exceedingly complex manner, 
forming a mass with so many passages and perforations that 
the term “spongy bones” has been applied to them. 

_ The most posterior is the larger, and placed rather higher 
than the other ; its anterior extremity (/7Z’) overlapping it. 
It completely fills the proper olfactory chamber ; its hinder 
extremity occupying the gap left in the cranial wall in front 
of the anterior segment of the brain-case. The various 
laminz are all connected together and to the hinder end of 
the mesethmoid, by a plate of bone (CZ) so full of perfora- 
tions of varied form and size that it is called the cribriform 
plate, and from it the name of e¢hmozd (or sieve-like) is 
commonly applied to all the bony structures with which 
it is united. On their outer side these laminez are con- 
nected to a thin flat plate of bone (the so-called os planum) 
which lies against the inner wall of the maxillary, but does 
not ordinarily contract any union with it. 

This bone results from the ossification of the complexly 
folded cartilage, over the surface of which the olfactory 
nerves are spread, the division into laminz permitting a 
great increase of sensitive surface. As, although originally 
distinct, it subsequently unites with the mesethmoid, by 
means of the cribriform plate, it is considered in human 
anatomy as part of the same bone, under the name of 
“lateral mass of the ethmoid,” and is described as con- 
sisting of the superior and middle “ turbinated bones ;” but 


110 tae SKOLL [CHAP. 


the name e¢hmoturbinal, applied to it by Professor Owen, is 
perhaps more appropriate. 

The uppermost of the lamella of the ethmoturbinal, lying 
immediately under the nasal bones, is rather distinct from 
the others, and extends much further forwards ; and as in 
certain Mammals it becomes united by bone with the nasal, 
it is sometimes distinguished under the name of zasotur- - 
binal. 

{n front, and on a rather lower level, a similar, but smaller 
and less complex bone (477), consisting chiefly of horizontal 
lamelle, is placed. ‘This, though originally developed from 
the same cartilage lining the outer wall of the nasal chamber 
as the last, ossifies quite distinctly from it, and contracts a 
bony union by a horizontal lamella on its outer side with 
the maxilla. This is the saxzloturbinal, and corresponds 
with the ‘“‘inferior turbinated bone” of human anatomy. 

It will be observed, that while the ethmoturbinal is placed 
high in the nasal cavity, and above the direct channel by 
which the air passes to the posterior nares, the maxillo- 
turbinal, situated nearer the front of the chamber, before it 
has divided into an upper true olfactory chamber and a 
lower narial passage, nearly blocks up the whole cavity, so 
that air passing through in inspiration is filtered between its 
meshes. The moist membrane which covers its bony plates 
in life is supplied with nerves chiefly from the fifth pair, 
and not from the olfactory ; so that it does not perform the 
function of an organ of smell like the ethmoturbinal, but 
rather serves to guard the entrance of the respiratory 
passages from foreign substances, and perhaps to warm the 
inspired air. 


In describing the walls of the cranium, a large space was 
mentioned on each side, between the posterior and middle 


FX] OK ZAE DOG. IVE 


cranial segment, in which were inserted certain bones not 
yet noticed. These bones form a definite group by them- 
selves, at all events locally connected, though very different 
in function and structure. 

In a mass of cartilage, in the position just indicated, 
ossification takes place from several centres (three, called 
respectively pro-otic, epiotic, and ofisthotic, according to 
Professor Huxley and others, in the human skull ;* but the 
process has not been accurately traced in other Mammals). 
These very rapidly unite to form a single bone, which com- 
pletely encloses the labyrinth or essential organ of hearing, 
consisting of the vestibule, semicircular canals, and cochlea. 
This bone is the feriotizc (Per). It is divided into two por- 
tions: an antero-internal, which forms a somewhat angular 
projection within the cranial cavity, and is of remarkable 
density—the fe‘rous portion; and a postero-external, a sort 
of process from the former, smaller, less dense, and forming 
a small portion of the wall of the cranium, appearing 
externally just in front of the exoccipital—the mastord 
portion. 

The petrous is of. course the more important, and has 
constant characters throughout the class, while the mastoid 
is very variable, and sometimes can scarcely be said to exist. 
It is in no case a separate bone ; and, although a portion of 
it may develop originally from a separate centre, it is always 
before birth firmly united with the petrous, so that they 
will be spoken of here as one bone, under the name of 
pertotic. 

The essential characters of the petrous portion of the 
periotic are, that it contains within it the internal ear ; 
that it has on its inner or cranial side a foramen, through 
which the facial and the auditory nerves leave the cranial 


1 Elements of Comparative Anatomy (1864), p. 148. 


Pr? EIS SISO LL [CHAP. 


cavity, the former to pass through the bone, escaping by the 
stylomastoid foramen on the outer and under surface, the 
latter to be distributed on the sensitive portions of the 
organ of hearing; and that it has on its outer side two 
holes, one placed above the other, the fenestra ovalis and 
the fenestra rotunda, through which the internal ear com- 
municates with the cavity of the tympanum, or middle-ear, 
which is situated on the outer side of the petrous part of 
the periotic bone. 

Externally to the periotic bone are placed two bones 
separately developed in fibrous tissue, which often acquire a 
very close connection with the periotic, occasionally, as in 
Man, becoming firmly ankylosed with it. 

The upper one of these is the sguamosal (Fig. 47, S9), 
which has a broad, scale-like, vertical portion spreading out 
over the side of the cranial wall, uniting with the supra- 
occipital behind, overlapping the lower edge of the parietal 
and the hinder part of the alisphenoid, and also appearing 
for a very small space in the inner side of the cranial wall. 
From near its lower berder it sends a strong process out- 
wards, which soon curves forwards, called the sygomatic 
process. This articulates with another bone (J/a), the malar 
or juga’, which connects it with the maxilla, and so forms 
the strong, lateral, nearly horizontal, or slightly arched 
osseous bridge, which passes from the face to the hinder 
part of the cranium, called the zygomatic arch. On the 
under surface of the base of the zygomatic process of the 
squamosal is a laterally extended, oblong surface, concave 
from before backwards, for the articulation of the condyle 
of the lower jaw, called the glenoid fossa (gf), the hinder 
edge of which is projected into the fostevenoid process (gp). 

The lower bone, on the outer side of the periotic, is 
the “ympanic (Ty). At birth this is a mere osseous ring, 


IX.] OF THE DOG. 113 


incomplete above, surrounding the inferior three-fourths of 
the membrana tympani, but it undergoes a considerable 
development in the course of the first few months. The 
external edge of the ring is produced horizontally outwards 
to form the short, bony, external auditory meatus; while 
the under and inner surface is greatly expanded, to form 
the conspicuous rounded prominence, hollow within, called 
the auditory bulla, which abuts against the outer edge of 
the basioccipital below.* 

The space that is left among this group of bones,—bounded 
by the periotic (the part in which the before-mentioned 
fenestree are situated) within, the periotic and squamosal 
above, the tympanic and its bullate expansion below, behind, 
and in front, and by the meatus auditorius externus, closed 
in the natural state by the membrana tympani, to the outer 
side,—is called the ¢ympanzc cavity. 

It contains within it the ossicula auditus, three small 
bones called malleus, znucus, and stapes, which, articulated 
together, stretch across the cavity from the membrana 
tympani to the fevestra ovalis.2 The cavity has an opening 
at its antero-internal angle, through which the Eustachian 
tube, connecting the tympanum with the pharynx, passes. 

The inner side of the bulla is perforated lengthwise 'by a 
canal, which commences posteriorly within the margin of 


1 The whole of the bulla is generally considered as belonging to the 
tympanic bone, but its inner part in many mammals is developed in a 
distinct cartilaginous lamella, interposed between the lower edge of the 
tympanic ring and the base of the skull. This may ossify from a sepa- 
rate nucleus, or by extension of bony deposition inwards from the true 
tympanic. The development of this region of the skull in the Mam- 
malia still offers an interesting field for investigation. 

* As these bones are, in the Mammalia, completely subservient to 
the organ of hearing, their modifications will not be described in the 
present work. 


114 ITE SKOLL [CHAP. 


the foramen lacerum posterius (between the auditory bulla 
and the exoccipital), and transmits the internal carotid artery. 
This vessel appears again on the surface, at the anterior 
extremity of the bulla, close to the Eustachian orifice ; then 
runs upwards and inwards and enters the cranium through 
the foramen Jacerum medium. 


This completes the enumeration of the bones of the 
cranium. Before proceeding further, it will be desirable 
to take a general survey of this part as a whole, pointing 
out the most prominent features of its various surfaces. 

The posterior surface is, 11 a general sense, a vertical 
wall, somewhat triangular in form, broad below and pointed 
above. In the middle line, at its lowest border, is the nearly 
round foramen magnum, bounded by the supraoccipital 
above, the exoccipitals on each side, and the basioccipital 
below. On the sides of the foramen magnum, and 
approaching each other in the middle line below, but 
diverging above, are smooth eminences, the occipital 
condyles. Further outwards, and separated from these by 
a deep valley, are the paroccipital processes, projecting 
backwards and downwards. Outside of the upper part or 
origin of these processes, the mastoid portion of the periotic 
appears on the hinder wall of the skull. The remainder of 
the region is formed by the supraoccipital, and it is dis- 
tinctly marked off laterally by ridges, which, commencing 
in the median line above, run downwards and outwards, 
at the junction of the parietals and supraoccipital, and are 
continued on the squamosal in front of the mastoid to the 
upper edge of the external auditory meatus. The ridges 
of each side taken together form the /ambdord or occipital 
crest. ‘They are far more conspicuous in old than in young 
animals. 


1x.] OF THE DOG. 115 


The superior surface of the skull (Fig. 46) may be divided 
into a cranial and a facial portion. The former is of a 
somewhat oval form. On its upper surface posteriorly, in 
full-grown dogs, is a median ridge joining behind with the 


Fic. 46.— Upper surface of cranium of a Dog, 3. SO supraoccipital; /P inter- 
parietal; Pa parietal; Sg squamosal; /7 frontal; 47a malar; Z lachrymal : 
Mx maxilla; Na nasal ; Px premaxi'la ; ag anterior palatine foramen ; zo infra- 
orbital foramen ; fof postorbital process of frontal boue. 


superior angle of the occipital crest, and dividing anteriorly 
into two less elevated ridges which curve outwards to the 
superior posterior angle of the orbit. . This ridge, as long 


12 


116 LHE SOLE [CHAP. 


as it is single and median, is called the sagzt/al crest. It 
bounds superiorly a large surface on the side of the skull, 
limited behind by the occipital crest, and below by the 
zygoma, called the ‘temporal fossa,’ from which the 
temporal muscle takes its origin. In young dogs the upper 
boundary of the surface for the origin of this muscle 
is of less extent, not reaching so high as the middle 
line of the cranium, and is but obscurely indicated on the 
comparative smooth surface of the skull. As the muscle 
increases in development its surface of ongin gradually 
ascends until it reaches the middle line, and with advancing 
age a still larger space is afforded for it by the gradual 
erowth of the sagittal crest. 

These changes in the upper part of the skull during 
growth have been particularly noticed, because they take 
place in very many arimals, and, without altering in the 
least the actual form of the brain-case, give rise to a very 
different external appearance of the skull, either in mem- 
bers of the same species, or in different but allied species. 

The upper part of the skull, in front of the diverging 
houndary lines of the temporal fossa, is expanded and some- 
what flattened, and has on each side a triangular process 
(pof), which curves somewhat downwards, and indicates 
the division of the temporal fossa behind from the orbit 
in front. This is the fostorbital process cf the frontal bone. 
It is connected by a ligamentous band, in the living animal, 
with a corresponding process arising from the zygoma ; 
but when this is removed the orbit and temporal fossa are 
widely continuous, their respective limits being only in 
dicated by the above-mentioned processes. 

The face is produced considerably in front of the orbits, 
and not only becomes more depressed, but also more 
compressed laterally, and is obliquely truncated anteriorly, 


Ix. ] OF THE DOG. 117 


terminating in the rounded incisor border of the premaxiila 
(PMx) ; above which is placed the subcircular orifice of 
the anterior nares. 

The upper, and a considerable portion of the lateral, 
surface of the cranium behind is formed by the parietal 
bones (fa), having the narrow interparietal (7?) ankylosed 
with the supraoccipital (SO), extending between them for 
about half their length. In front of this the parietals are 
-commonly united together by bone in old dogs. 

Anteriorly to the parietals, the upper part of the temporal 
fossa, the frontal plateau between the orbits, and the upper 
half of the inner wall of the orbit, are formed by the frontal 
bone. The remaining or lower portion of the temporal fossa 
is formed by the squamosal behind and by the alisphenoid 
in front. On the inner or cranial surface of the confluent 
orbital and temporal fossze, a wide groove runs obliquely 
downwards and backwards, which may be considered as the 
boundary line of these two regions. In the lower part of this 
groove are several large foramina placed in linear series. 
The highest is the optic foramen, the next (of larger size) 
the sphenoidal fissure, and the third the foramen rotundum 
and anterior opening of the alisphenoid canal. The orbit 
has no floor except for a very short space in front ; the 
lower border of its inner wall passing directly into the outer 
surface of the vertical ridge formed by the pterygoid, the 
pterygoid process of the alisphenoid and the palatine bones, 
and continuing the outer wall of the narial passage back 
wards beyond the bony palate. The palatine bone forms a 
considerable part of the inner wall of the orbit, joining the 
frontal anteriorly, though separated from it for a considerable 
space posteriorly by the orbitosphenoid. The lachrymal (Z) 
appears in the anterior boundary of the orbit, the malar (J/a) 
joins its outer boundary, and the upper surface of the hinder 


118 HE SKOLL [CHAP. 


end of the alveolar border of the maxilla projects back- 
wards, so as to form a partial floor to its anterior extremity. 


Fic. 47.—Under surface of the cranium of a Dog, 4. SO supraoccipital; 4x0 
exoccipital ; LO basioccipital; Pex mastoid portion of periotic; 7y tympanic 
bulla; SS basisphenoid ; Sg zygomatic process of squamosal; J7a malar; AS 
alisphenoid ; P¢ ptery goid ; PS presphevoid ; “7 frontal; Vo vomer ; PZ palatine ; 
Ma maxilla; PA/x premaxilla; fz foramen magnum; oc occipital condyie; 
pp paroccipital process ; cf condylar foramen ;_ /Z4 foramen lacerum posterius; s7z 
stylo-mastoid foramen ; eazz external auditory meatus ; gf postglenoid foramen : 
gp postglenoid process; gf glenoid fossa; fz foramen lacerum medium; _/o 
foramen ovale ; as posterior opening of alisphenoid can+1; /~ foramen rotundum 
and anterior opening of alisphenoid canal: sf sphenoidal fissure or foramen 
lacerum anterius ; of optic foramen ; Zf/ posterior palatine foramen ; aff auterior 


palatine foramen. 
\ 


In front of the orbits the face is formed above by the 


ed OF £AE: DOG. 119 


long narrow nasals (Va) pointed behind, and widening and 
obliquely truncated in front to form the upper border of 
the narial aperture; on each side by the maxilla (JZx), 
having near the middle of their surface the large zzfraorbital 
foramen (to), through which the terminal branches of the 
second division of the fifth or sensory nerve of the face pass 
to be distributed to the upper lip and whiskers ; and quite 
anteriorly by the premaxille (Pd7x), which complete the 
boundaries of the nares, and send up narrow processes 
between the nasals and maxillz, towards, though not meet- 
ing with, similar processes which run from the frontals. 

The 7ferior surface of the skull (Fig. 47) is formed 
anteriorly by the nearly flat, elongated surface of the palate, 
narrower in front than behind, composed anteriorly of the 
premaxillz (P4/x) ; then of the maxillee (47x), which diverge 
posteriorly and allow the palatines (/7) which form the 
hinder border to reach in the middle line almost to the centre 
of the palatal surface. In front and at the sides this surface 
is bounded by the alveolar borders of the premaxille and 
maxillze, in which the teeth are set. Anteriorly are two con- 
siderable oval foramina (aff), placed longitudinally very near 
the middle line, formed mainly in the premaxille, though 
their boundary is completed posteriorly by the maxille ; 
these are the anterior palatine foramina. ‘The naso-palatine 
nerve descends through them to spread over the anterior 
surface of the soft palate. Not far from the hinder border of 
the palate, and more distant from the middle line, near the 
suture between the maxilla and palatine, are several much 
smaller foramina (fostertor palatine), also for the transmission 
of branches of the fifth nerve and blood vessels. 

The truncated median part of the hinder edge of the palate 
forms the lower margin of the posterior narial aperture. 
Laterally, the palate bones are continued backwards as 


120 Pie SOL L. [CHAP. 


vertical plates, thick and rounded below at first, but 
gradually becoming more compressed. These are continued 
still further backwards by the compressed pterygoid bones 
(Pz), ending in the backward-projecting Aamular processes, 
and supported externally by the descending (pterygoid) plate 
of the alisphenoid. The groove between these descending 
lamellee of bone continues the narial passage backwards. It 
has for its roof the vomer (V0) in front, then the presphenoid 
(PS), and posteriorly a portion of the basisphenoid (45) ; 
but the palatines and pterygoids arch over so much towards 
the middle line that they only leave a small strip of these 
bones exposed. Inferiorly, this groove is not closed by 
bone, but in the living animal the soft palate is stretched 
across It. 

The base of the skull, behind this “‘mesopterygoid ” 
fossa, presents in the middle a nearly flat elongated surface, 
consisting of the basisphenoid (2S) and basioccipital (BQ) ; 
the latter, roughened for the attachment of muscles, and 
terminating posteriorly at the inferior border of the foramen 
magnum (/7), flanked on each side by the occipital condyles 
(oc). The nearly straight.lateral edges of the anterior half 
of the basioccipital rise up to abut against the prominent 
smooth rounded auditory bullz (7Zy), which form so con- 
spicuous a feature in this region of the skull, and which are 
produced outwards into the lower wall of the external 
auditory meatus (eam). In the antero-internal angle of the 
bulla is seen the irregular orifice of the Eustachian canal. 
Close to the inner side of this is an oval aperture, which is 
at the same time the anterior extremity of the carotid canal 
and the entrance to the foramen lacerum medium (//7) 
through which the internal carotid artery enters the cranial 
cavity. In front, and rather to the outer side of this, is the 
foramen ovale (fo) piercing the alisphenoid, and immedi- 


EX OF THE. DOG. 121 


ately before this is a round aperture (as) leading to a short 
canal running horizontally forwards through the same bone 
at the root of its pterygoid process, and opening anteriorly 
into the foramen rotundum (/7). Through this the external 
carotid artery runs for part of its course, and it has been 
called the alisphenotd canal 

In front of the outer side of: the auditory bulla is the 
glenoid fossa for the articulation of the mandible, bordered 
behind by the conspicuous curved fostelenoid process (gp). 
Immediately behind this the root of the zygoma is pierced 
by a large hole, postglenord foramen (pgf), through which a 
vein passes out from the lateral sinus within. 

Behind the auditory bulla, to the inner side, is the large 
Joramen lacerum postertus ( flip), and, situated deeply within its 
recesses, the posterior opening of the internal carotid canal. 
On aridge of the exoccipital, between this large foramen 
and the depression immediately in front of the condyle, is 
the small, nearly circular condylar foramen (cf), and at the 
outer termination of the same ridge rises the conical paroc- 
cipital process (ff), abutting at its base against the hinder 
end of the auditory bulla. Immediately behind the bulla, 
and to the outer side of the abutment of the paroccipital 
process against it, is an oval hole (sm), partially divided by 
a constriction into an inner and an outer division. In 
the inner division the end of a small cylindrical plug of 
bone, the zympanohyal, can generally be seen. ‘The outer 
division is the stylomastoid foramen, through which the 
seventh nerve, or portio dura, makes its exit. The bone 
forming its outer boundary is the mastoid portion of the 
periotic. 

1 See H. N. Turner’s ‘‘ Observations relating to some of the Foramina 
in the Base of the Skull in Mammalia,” &c., Proc. Zool. Soc. 1848, 
p- 63. 


122 THEW SKROLL [CHAP. 


Connected with the posterior lateral parts of the cranium 
are two appended bony parts: the lower jaw or mandible, 
and the hyoidean apparatus. The former forms the frame- 
work for the floor of the mouth, and supports the lower 
series of teeth; the latter gives a firm yet movable point 
of attachment to the root of the tongue and to the larynx, 
or organ of voice. 

The mandible consists of two symmetrical elongated rami 
(see Fig. 45, p. 97), diverging bebind, and coming in contact 
in front at the middle line, by a roughened surface called the 
symphysts (s); here they are firmly held together by inter- 
posed fibrous tissue, or in old animals they may become 
ankylosed. 

Each ramus is compressed from side to side, has a 
thickened rounded lower border, slightly curved in the 
longitudinal direction, and a nearly straight upper alveolar 
border, in which the teeth are implanted. The inferior 
border inclines upward in front to meet the alveolar border 
at the front of the symphysis. Near the posterior extremity 
is the condyle (cd), a transversely-extended projection, with its 
upper surface rounded in the antero-posterior direction, and 
which, fitting into the glenoid cavity of the squamosal bone, 
forms the hinge-like synovial articulation by which the lower 
jaw moves on the skull. The upper border, between the 
condyle and the hindermost tooth, rises into a high, com- 
pressed, recurved process (the coronotd process, ch), to which 
the temporal muscle is attached. ‘The outer surface of this 
process gradually subsides into a considerable hollow in the 
side of the ramus, with prominent anterior, inferior, and 
posterior edges, to which the masseter, another powerful 
muscle for closing the jaw, is attached. 

The point at which the vertical hinder edge of the ramus, 
descending from the condyle, meets the horizontal inferior 


IX. | OF THE DOG. 123 


border, is called the angle, which in the Dog is prolonged 
into a conspicuous compressed process, with an upturned and 
slightly inverted pointed extremity, the angular process (a). 
On the inner side of the ramus, a little way in front of and 
below the condyle, is the zz/erior dental foramen (22), for the 
admission of the inferior dental nerve (from the fifth pair) 
and artery. On the outer side of the ramus, near its anterior 
extremity, is the mental foramen, through which a branch of 
the same nerve passes out to the lower lip and surrounding 
structures. 


Fic. 48.—Extracranial portion of hyoidean apparatus of Dog, front view. sz stylo- 
hyal ; e% epihyal; ch ceratohyal (these three constitute the ‘‘anterior cornu”’) : 
bh basihyal, or ‘‘ body” of hyoid ; ¢/ thyrohyal, or ‘‘ posterior cornu.” 


The hyoidean apparatus (Fig. 48) consists of a median 
portion below, the dasif#yal (bh), from which two pairs 
of half arches, or “ cornua,” extend upwards and outwards. 
The anterior (ch to sh) is the largest, and connects it with 
the cranium. The posterior (¢#) is united externally or 
superiorly with the thyroid cartilage of the larynx. In the 
Dog there are four distinct ossifications in the anterior arch. 
The first is a small cylindrical piece of bone lying in a 
canal between the tympanic and periotic bones, immediately 
to the inner and anterior side of the stylomastoid foramen, 


124 LE SOLE [CHAP. 


and by its upper end firmly ankylosed with the surround- 
ing bones. It can be seen much more distinctly in some 
dogs’ skulls than others, and is more conspicuously de- 
veloped in some other Mammals. ‘This I have called ¢ym- 
panohyal, as it is always in relation with the hinder edge 
of the tympanic bone, generally more or less surrounded by 
it, and it extends upwards, embedded in, and afterwards 
ankylosed with, the periotic, to the hinder wall of the 
tympanic cavity. Its lower end is truncated and con- 
tinued into a band of cartilage, which connects it with 
the proximal end of the bone which has been generally 
recognised as the uppermost of the series forming the 
anterior hyoidean arch, the stylohyal (sh). The two suc- 
ceeding bones (ef and ch) are named by Professor Owen 
respectively e¢pzhyal and ceratohyal. All three are elon- 
gated, compressed, slightly curved or twisted on them- 
selves, tipped at each end with cartilage, and connected 
with each other by synovial joints. The stylohyal and 
epihyal are nearly equal in length, the ceratohyal shorter 
and stouter. 

The dasthyal (bh) is a transversely-extended, flattened bar, 
with its extremities rather upturned and thickened. The 
posterior cornu (¢h) consists of a single, nearly straight, 
compressed bone, the ¢hyrofyal, articulated inferiorly with 
the outer end of the basihyal, just below the attach- 
ment of the ceratohyal, and truncated at its superior ex- 
tremity, to which the thyroid cartilage of the larynx is 
suspended. 


Development of the Skull,—F¥or a detailed and beautifully 
illustrated account of the early development of the Mam- 
malian skull, I must refer to Professor Parker’s monograph 
“On the Structure and Development of the Skull in the 


ad P 
an ———— ee 


Ix: ] OF LAE DOG. 125 


Pig” (Philosophical Transactions, 1874), of which the fol- 
lowing is a brief summary. 

- The notochord (see p. 16) extends into the basicranial 
axis only as far as the hinder border of the pituitary body, 
corresponding with the middle of the future basisphenoid 
bone. 

The skull is formed from — 

a. A cartilaginous basicranial plate, embracing the 
anterior extremity of the notochord. 

b. A series of five paired descending cartilaginous arches, 
developed in the visceral laminze, constituting the sides of 
the face and neck ; of which two are in front of, and three 
behind the mouth. 

c. A pair of cartilaginous auditory capsules. 

d. A pair of cartilaginous nasal capsules. 

The basicranial plate grows up as an arch over the 
occipital region of the skull, and coalescing with the auditory 
capsules laterally gives rise to the primordial skeleton of 
the occipital, periotic, and basisphenoidal regions of the 
skull: the parietal and frontal regions being afterwards 
completed by ossification in membrane surrounding the 
cranial cavity. 

Of the arches, the first pair, constituting the trabecule 
cranit, pass forward from below the front end of the basi- 
cranial plate, enclosing the pituitary body, in front of which 
they coalesce, and together with the olfactory capsules, give 
rise to the presphenoidal, and ethmoidal regions of the 
cranium (see Diagram on p. 106, I.). 

The second arch ( plerygo-palatine)' gives rise to the ptery- 
goid, palatine, maxillary and malar regions, (II.). 

The cleft between this and the next arch is the mouth. 


! This is more properly an outgrowth from the third, than an inde- 
pendent arch. 


126 TT EOSRULL, [CHAP. 


The third, or first post-oral arch (III.), called the first, 
in the older and more usual nomenclature, consists of 
Meckel’s cartilage, a slender rod, in relation above with the 
periotic region of the skull. Of this, in the Mammalia, the 
upper extremity becomes converted into the mad/eus, one 
of the small bones in the tympanic cavity, while in con- 
nection with the lower or distal part, the ramus of the man- 
dible or lower jaw is developed partly by conversion of the 
cartilage itself, but principally by the ossification of fibrous 
or cartilaginous tissue deposited around it. The upper end 
of the ramus afterwards acquires a secondary articular con- 
nection with the squamosal bone, its primitive connection 
with the malleus entirely disappearing. 

The cleft which les behind this arch becomes contracted 
into the Eustachian tube, tympanic cavity, and meatus 
auditorius externus, which would form a canal of commu- 
nication between the pharynx and the external surface but 
for the interposition of the delicate membrana tympant. 

The rod .of cartilage forming the fourth visceral arch 
(IV.), or second post-oral, becomes the anterior hyoid areh, 
its proximal extremity being modified into the zcus.} 

From the fifth arch (third post-oral), which corresponds 
to the first branchial of branchiate vertebrates, is formed 
the posterior hyoid arch, or thyrohyal. (V.) 


Some of the changes which take place in the cranium while 
advancing from youth to maturity have already been noticed ; 
but it will be well, before proceeding to describe the modi- 
fications of the mammalian skull, to mention certain others 
which take place, to a greater or less degree, in all skulls. 


1 The stapes, according to Parker, is formed independently of the 
visceral arches, in a budding of the outer cartilaginous wall of the 


auditory bulla. 


oe 


ix] OF DHE L0G. 127 


These depend mainly on the fact that the brain, and con- 
sequently the cavity which contains it, and also the sense 
capsules, increase in size in a much smaller ratio than the 
external parts of the head, especially the jaws and _ pro- 
minences for the attachment of muscles. The dispropor- 
tionate growth and alteration of form of these parts, 
concomitant with little or no change in the brain-case, is 
effected partly by increase in thickness of the bones, but 
mainly by the expansion of their walls and the develop- 
ment of cells within, which greatly extend the outer surface 
without adding to the weight of the bone. 

In the Dog these cells are developed chiefly in the fore 
part of the frontal bones, constituting the frontal sinuses, 
and in the presphenoid, constituting the sphenotdal sinuses. 
Air passes freely into them from the nasal passages. In 
many animals they attain a much larger extent than in the 
Dog, reaching their maximum in the Elephant (see Fig. 60, 
p. 181), where the alteration of the external form of skull 
during growth, without material change in the shape or size 
of the cerebral cavity, is strikingly shown. At the same 
time the alveolar borders of the jaws gradually enlarge to 
adapt themselves to the increased size of the permanent 
teeth which they have to support, and the various ridges and 
tuberosities for the attachment of muscles become more 
prominent. 

During these changes a gradual consolidation takes place 
in the structure of the skull generally, by the partial or com- 
plete union of certain of the bones by synostosis. The 
union of the different bones generally proceeds in a certain 
definite order, which, however, varies much in different 
species. Sometimes it extends so far as to lead to complete 
obliteration of all the cranial sutures. 


CHAPTER: ax. 


THE SKULL IN THE ORDER PRIMATES, CARNIVORA, 
INSECTIVORA, CHIROPTERA, AND RODENTIA. 


ORDER PRIMATES. J/an.—On comparing a longitudinal 
and vertical section of a young human skull, in which most 
of the sutures are still distinctly seen (Fig. 49), with that of 
the Dog, it will be seen to be composed of the same bones, 
having very nearly the same connections, and yet the whole 
form is greatly modified. This modification is mainly due 
to the immense expansion of the upper part of the middle 
or cerebral fossa of the brain cavity, which not only carries 
the roof of the cavity a great distance from the basicranial 
axis, but also forces, as it were, the anterior and posterior 
walls from the vertical nearly to the horizontal position, so 
that they are, roughly speaking, in the same line with the . 
short basicranial axis, instead of being perpendicular to it. 
In addition to this great difference, the facial portion of the 
skull is deeper from above downwards, and very much 
shorter from before backwards. 

Taking a survey of the human skull in the same order 
as was done with that of the Dog, we find the craniofacial 
axis, composed of the basioccipital bone (2O), terminating 
at the anterior border of the foramen magnum (/m) behind, 
and in this young skull still separated from the basisphenoid 


CHAP, X.] FHE SKG@GLEL OR SVAN, I 


to 
Ne) 


Fic. 49.—Vertical, longitudinal, median section of a young human skull, with the first 
dentition, 3. Asin the other sections of skulls figured, the mandible is displaced 
downwards, so as to show its entire form Wax premaxilla; JZ7 maxillo- 

“turbinal : ET ethmo-turbinal; 4/£ ossifi-d portion of the mesethmoid ; Va nasal ; 
cg crista galli of the me ethmoid; OS orbitosphenoid, or lesser wing of the 
sphenoid; AS alisphenoid, or greater wing of the sphenoid; /*7 frontal; 7’ 
pariecal; SO supraoccipital; JZ mastoid portion of the periotic ; Sg squamosal ; 
Per petrous portion of the periotic ; the large foramen below the end of the line 
is the internal auditory meatus, the small depression above it is the nearly- 
obliterated floccular fossa. xO exoccipital, the line points to the condylar fora- 
men; /z foramen magnum; BO basioccipital ; BS basisphenoid ; s¢ sella turcica ; 
PS presphenoid, ankylosed with the basisphenoid, forming the ‘‘ body of the 
sphenoid ;” P¢ pterygoid ; PZ palatine ; Vo vomer ; 47x maxilla; s symphysis of 
mandible ; cf coronoid process ; ca articular condyle ; @ angle; sf stylohyal, or 
‘*styloid process of temporal ;” c/ ceratohyal, or lesser cornu of hyoid ; 44 basi- 
hyal, or body of hyoid ; #4 thyrohyal, or greater cornu of hyoid. 


K 


130 Ltd Ee SIOCLL, [CHAP. 


in front by a vertical fissure. The daszsphenoid (BS) is short 
and deep, and has a strongly marked pituitary fossa or “sella 
turcica” (st) above. It has completely united with the pre- 
sphenoid (PS), though at birth the line of separation (below 
the spot called the ofivary process or tuberculum selle) is still 
visible. In adult age large air-cells fill the interior of this con- 
joined bone, which is the “‘ body ” of the so-called “ sphenoid” 
of human anatomy. Anteriorly the presphenoid narrows to 
a sharp vertical edge, which is in contact with the mesethmoid 
(AZZ) above and the vomer (/’0) below. The whole of the 
upper part of the mesethmoid is ossified in the specimen 
described, constituting the “ lamina perpendicularis,” but the. 
anterior and lower part forms the septal cartilage of the nose. 
Its upper border forms a strong compressed triangular pro- 
jection into the cranial cavity, called the “crista galli” (a). 

The posterior segment of the brain-case is completed, as 
in the Dog, by the pair of exoccipitals (#xO), and a large 
supraoccipital (SO).!_ The triangular upper part of the latter 
may be considered to represent the interparietal, though it 
very soon becomes incorporated with the rest of the supra- 
occipital. The middle segment is completed by large ali- 
sphenoids (AS), the “ greater wings of the sphenoid bone,” 
and enormously extended, somewhat square-shaped parietals 
(Pa); the frontal segment by narrow triangular orbito- 
sphenoids (OS), the “lesser wings of the sphenoid bone,” ? 
and by large arched frontals (77). 

Of the fossze into which the cranial cavity is divided, the 
olfactory fossa is very small, rather narrow, elongated, and 


1 The ‘‘ occipital bone” of human anatomy is formed by the coales- 
cence of the basioccipital, exoccipitals, and supraoccipital. 

* The ‘‘sphenoid bone” of human anatomy is formed by the union 
of the basisphenoid, presphenoid, alisphenoids, orbitosphenoids, and the 
pterygoids. The basal portion ultimately ankyloses with the occipital. 


x.] MAN. 131. 


shallow. The cribriform plate which closes it in front, in- 
stead of being vertical, as in the Dog, is horizontal, and 
almost in the same line with the basicranial axis. It is 
bounded in the median line, and separated from the cor- 
responding fossa of the other side by the prominent crista 
galli of the mesethmoid. The middle fossa is, as before 
said, of comparatively enormous extent ; it is bounded pos- 
teriorly by the tentorial ridge, having the same relations to 
bones as in the Dog, but lying more horizontally and being 
far less prominent, having no osseous shelf-like inward exten- 
sion. This fossa is distinctly divided into an anterior and 
posterior portion, by the strongly projecting hinder ridge of 
the orbitosphenoid. The floor of the anterior portion is 
arched in consequence of the inward projection of the roof 
of the orbit, while the floor of the posterior, or “temporal 
fossa,” is deeply concave. The cerebellar fossa is of mode- 
rate size, and lies entirely underneath the hinder part of 
the cerebral fossa. 

The “sella turcica,” or depression in the basisphenoid for 
the lodgment of the pituitary body of the brain, is bounded 
posteriorly by an elevated transverse ridge, the corners of 
which are called the ‘posterior clinoid processes.” Cor- 
responding processes projecting backwards from the orbito- 
sphenoids are called ‘anterior clinoid processes.” 

The foramina in the base of the skull scarcely differ from 
those of the Dog. 1. The olfactory has been already 
described. 2. The optic is a large round hole close to the 
inner and posterior part of the orbitosphenoid. 2) he 
sphenoidal fissure is larger than in the Dog, and produced 
externally into a long narrow slit. 4 and 5. The foramen 
rotundum and the foramen ovale pierce the alisphenoid, one 
near its anterior, the other near its posterior border. Close 
behind the last-named is a small hole (“foramen spinosum ”’), 

K 2 


132 THE SKULL. [CHAP. 


through which a branch of the external carotid artery 
(middle meningeal) enters the brain-cavity. 6 and 8. The 
foramen lacerum medium basis cranii and the foramen 
lacerum posterius have the same functions and relation as 
in the Dog. 7. Between these two the periotic has the 
conspicuous meatus auditorius internus on its inner side. 
The depression above this, for the lodgment of the floc- 
culus, is distinctly seen in foetal human skulls up to the 
time of birth, but it afterwards becomes gradually oblite- 
rated. 9. The condylar foramen perforates the exoccipital, 
as in the Dog ; and lastly (10), the foramen magnum has 
the same general subcircular form, and is bounded by the 
same bones, but differs greatly in direction, its plane looking 
mainly downwards instead of backwards. 

The nasal cavities differ chiefly from those of the Dog in 
their shortness and greater vertical height. In their inner 
wall, the descending median plate of the vomer (Vo) is 
much more developed. The pterygoids (P¢) are extended 
vertically, are narrow from before backwards, end below in 
a marked “hamular” process, and soon ankylose with the 
pterygoid plates of the alisphenoid anteriorly, but posteriorly 
are separated from them by a well-marked “ pterygoid 
fossa.” ! The palatines (77) and maxille (47x) are short 
from before backwards. The premaxillz (?4d/x) are small 
and early ankylosed with the maxille.? The nasals (/Va) 


1 The pterygoid, not being recognised as a distinct bone, is commonly 
described in works on human anatomy as ‘‘ the internal pterygoid plate 
of the sphenoid ;” the pterygoid process of the alisphenoid being the 
‘* external pterygoid plate.” 

2 The premaxilla is a distinct bone in the human fcetus, but is covered 
on its external or facial aspect by a process of the maxilla, which extends 
over it towards the middle line, and becomes completely fused with it 
before birth, so that no trace of the maxillo-premaxi lary suture is ever 
seen on the outer side of the face. On the inner and palatal aspect of 


x.] MAN. 133 


are short, and nearly vertical, broad below and narrow 
above. The anterior nares are also nearly vertical. The 
turbinal bones are comparatively little developed, and of 
simple structure, especially the lower or maxillo-turbinal 
(77). ‘The flat bony-plate on the outer side of the ethmo- 
turbinal or ‘fos planum,” instead of lying against the inner 
side of the maxilla, forms part of the outer wall of the nasal 
cavity and inner wall of the orbit, uniting with the frontal 
above, the lachrymal in front, the maxilla below, and the 
palatine behind. 

‘The group of bones placed around the organ of hearing, 
periotic, squamosal, and tympanic, though originally dis- 
tinct, become united together soon after birth, to form the 
so-called ‘“‘temporal bone.” ‘They differ from the corre- 
sponding bones in the Dog in the following particulars. The 
periotic has a very much larger mastoid portion (47), which 
forms a considerable part of the wall of the cerebellar fossa. 
In the new-born infant its outer surface is smooth 
and flat, but as life advances, air-cells become developed 
within it, communicating with the tympanic cavity, and 
a strongly-marked descending projection, the “ mastoid pro- 
cess,” appears on the lower and anterior part of its outer 
surface. The squamosal (Sg) is a large flat vertical plate, 
forming a considerable part of the wall of the posterior 
cerebral fossa, behind the alisphenoid. Its zygomatic pro- 
cess 1s comparatively slender and straight. The tympanic 
forms a long tubular external auditory meatus, but its inner 
part joins the periotic, forming the floor of the tympanic 
cavity without being inflated into an auditory bulla. Its 


the bones the suture is always evident at birth, and can often be traced 
even in adult skulls. See G. W. Callender ‘‘ On the Formation and 
Early Growth of the Bones of the Human Face.”’ (Phil. Trans. 1869, 
pe 163.) 


134 THE SKULL: [CHAP. 


under surface is produced into a rough ridge, to the inner 
side of which the large carotid canal perforates the base of 
the periotic, being directed obliquely forwards and inwards. 
In adult skulls the stylohyal becomes ankylosed with the 
tympanic and periotic, constituting the “‘styloid process of 
the temporal bone.” 

In examining the external aspect of the skull, the large 
smooth subglobular or oval brain-case, constituting by far the 
larger part: of the whole cranium, is strikingly different from 
that of the Dog. The occipital surface, instead of being ver- 
tical, is nearly horizontal. The condyles, instead of being at 
the hindermost part of the skull, are not far from the middle 
of the base. The paraccipital process of the exoccipitals 
are represented by mere rudiments, the so-called “ jugular 
eminences ;” on the other hand, the mastoid processes, 
almost obsolete in the Dog, are very greatly developed. The 
occipital crest is represented by a slightly raised and rough- 
ened line, the “ superior curved line,” and the sagittal crest 
is absent. 

The sutures connecting the bones of the upper surface 
of the cranium are remarkable for their wavy or indented 
character, processes from one bone interlocking with those 
from the other in a most complex manner, at least on the 
external surface, for seen from within they appear com- 
paratively straight and simple. There are very often 
irregular ossifications, separated from the contiguous bones, 
lying among the indentations of the occipito-parietal suture, 
called ‘‘Wormian bones.”* The temporal fossze are but 
indistinctly marked out by a curved line above, and are 
separated from each other by a wide expanse formed 


1 In works on human anatomy, the occipito-parietal suture is com- 
b 
monly cal'ed ‘‘ lambdoid ;” the interparietal, ‘‘sagittal;” and the 
fronto-parietal, ‘* coronal.”’ 


ey MAN. 135 


by the smooth rounded upper part of the parietal anil 
frontal bones. ‘The orbit is completely encircled by bone, 
the outer margin being formed by a process from the malar 
ascending to join the post-orbital process of the frontal; and 
it is, moreover, in great part separated from the temporal 
fossa by an extension inwards of the ascending process of 
the malar meeting the alisphenoid, although a communica- 
tion is left between the two cavities below in the “spheno- 
maxillary fissure.” ‘The axis of the orbital cavity is directed 
more forwards than in the Dog. The face is altogether very 
much shorter, broader, and flatter. 

In the inferior surface of the skull, the palate is seen 
to’ ‘be. much: -shorter:.and wider than; that of the: Doe: 
especially anteriorly, where its outline forms an almost 
semicircular curve. The maxillo-paiatine suture is nearly 
straight transversely, and so is the hinder border of the palate, 
though produced backwards into an obtuse spine at the 
middle line. The distance between the hinder border of the 
palate and the foramen magnum is much shorter relatively, 
the space between the pterygoids being particularly short 
and wide. The true pterygoids and pterygoid plates of the 
alisphenoid are widely separated posteriorly, leaving a con- 
siderable fossa between them; and the latter are larger 
and project further backwards than the former. The under 
surface of the tympano-periotic region is rough and irregular, 
instead of being smooth and bullate, and the perforation for 
the internal carotid artery is very conspicuous. ‘There is 
no alisphenoid canal, scarcely any postglenoid process, no 
distinct glenoid venous foramen, a very small paroccipital, 
and a very large mastoid process. By the inclination of the 
occipital surface downwards, instead of backwards, an 
inferior view of the skull includes nearly all this surface, 
with the large foramen magnum and the condyles. 


136 THE PSI LE, [CHAP. 


In accordance with the general form of the face the 
mandible is short. The two rami of which it is originally 
formed unite together at the symphysis within a year after 
birth. They are widely divergent behind, and approach 
"in front at a much more obtuse angle than inthe Dog. The 
horizontal portion of each ramus is deep and compressed, 
the lower margin straight or sughtly concave, and produced 
anteriorly rather in front of the alveolar margin, so as to 
occasion the mental prominence, characteristic of the human 
lower jaw. The anterior symphysial margin (Fig. 49, 5), 
therefore, instead of sloping upwards, from behind forwards, 
is vertical, or rather inclined in the other direction. Pos- 
teriorly, the condyle (cd) is more elevated than in the Dog, 
and is less transversely extended. ‘The coronoid process 
(cp) is smaller and less recurved. ‘The posterior border, 
between the condyle and the angle (a), is~ nearly straight 
and vertical, and the angle is rounded, compressed, slightly 
everted, and not produced into any hook-like process, as in 
the Dog. ‘The depression for the masseter muscle is very 
faintly marked. 

The hyoidean apparatus differs in several particulars from 
that of the Dog. The tympanohyal can generally be 
recognised in the skull of an infant at birth, and for a few 
years after, as a cylindrical piece or bone, with a truncated 
lower extremity, about one-twentieth of an inch in diameter, 
seated in a depression in the hinder border of the tympanic, 
immediately to the anterior and inner side of the stylo- 
mastoid foramen. Its upper end becomes soon ankylosed 
with the periotic. ‘lhe tympanic is produced around it an- 
teriorly, constituting the ‘‘ vaginal process.” The stylohyal | 
(sh), at first a long styliform piece of cartilage, continuous 
with the tympanohyal, commences to ossify by a separate 
‘centre before birth, and, at a very variable period after- 


x] MAN. a7 


wards, is usually ankylosed with the tympanohyal and sur- 
rounding cranial bones, constituting the so-called “ styloid 
process.” ‘This is a condition not met with in any other 
Mammal. Below the stylohyal the greater part of the an- 
terior hyoid arch is represented by a slender ligament (the 
“stylohyoid ” hgament), there being no ossification corre- 
sponding to the Dog’s epihyal; but the ceratohyal (c/) to 
which the ligament is attached below, is a small bony 
nodule, the “lesser cornu of the hyoid ” of human anatomy, 
which is articulated synovially to the upper corner of the 
outer extremity of the basihyal, though sometimes in old 
age becoming ankylosed. The basihyal (22), or “body of 
the hyoid,” is transversely oblong, hoilowed posteriorly, and 
deeper from above downwards than in the Dog. ‘The thy- 
rohyals (2) or “‘ greater cornua of the hyoid,” are elongated, 
nearly straight and somewhat compressed. They usually 
become ankylosed before middle life with the outer extre- 
mities of the basihyal. 


The Szmzina have the skull formed generally on the same 
plan as that of Man, with certain modifications in detail. 

The facial portion is enlarged and elongated as compared 
with the cerebral portion, though to a very variable extent 
in different members of the sub-order. 

In nearly all, the brain-cavity maintains the same general 
form asin Man, though it is usually of less comparative 
vertical extent. With few exceptions, the middle compart- 
ment for the lodgment of the cerebrum retains its 
relative situation and -superiority in size to the cerebellar 
and the clfactory fosse, completely overlying them both ; 
and consequently the occipital region of the skull with the 
foramen magnum behind, and the cribriform plate of the 
ethmoid in front, are in the same general horizontal line 


138 THE SKULL. _[cHap. 


with the basicranial axis as in Man, and not perpendicular 
to them as in the Dog. 

Tt is remarkable that the deviations from this general rule, 
especially as regards the plane of the occipital surface, are 
not in relation to the general position of the animals in a 
descending series, from Man to the lowest Monkeys; for the 
occipital surface is nearly vertical in the anthropoid Gibbons 
(Hylobates), especially A. syndactylus (the Siamang), and 
completely so in the American Howling Monkeys (A/yce¢es), 
where the cerebral fossa does not project in the least degree 
behind the cerebellar fossa ; while in the Baboons (Cyzoce- 
phalus), among the Old World Monkeys, and still more in 
some of the smaller and lower forms of American Monkeys 
(as Saimiris), the posterior development of the cerebral 
' fossa is so great as to throw the supraoccipital bone con- 
siderably more into the posteriorly prolonged base of the 
skull even than in man. 

The olfactory fossa is always small. It is not only very 
short, but, in consequence of the considerable projection 
inwards of the portion of the frontal forming the roof of the 
orbit on each side of it, is both narrow from side to side, 
and deep from above downwards. 

In most of the Szmzzva, including the Gorilla and Chim- 
panzee, the frontals meet along the middle line over the 
presphenoid, between the mesethmoid in front and the 
orbitosphenoids behind ; but the Orang agrees with Man in 
wanting this postethmoid union of the frontals, and so also 
do some of the Cebide. 

The fossa on the inner surface of the periotic for the 
floccular process of the cerebellum is almost obliterated in 
the adult Gorilla, Chimpanzee, Orang, and Gibbons, but is 
persistent, and often very large, in all other Monkeys. 

A partial ossification of the tentorium from the inner 


Pea | PRIMATES. 139 


edge of the periotic takes place in some of the American 
Monkeys, as AZycetes and Cebus. 

The suture between the basisphenoid and the _ pre- 
sphenoid remains distinct in the Baboons and all the lower 
Monkeys, until the animal has nearly attained its full size 
and acquired its permanent teeth; but it is completely 
obliterated, and the cancellous structure of the two bones is 
continuous, in the Gorilla, Chimpanzee, and Orang, while 
the animal still retains all its milk-teeth. 

The nasal cavities, with their surrounding bones, are 
generally longer and of less vertical extent than in Man, 
but, as in the case of the inclination of the occipital plane, 
not following any regular serial descent. Thus the propor- 
tions of these parts are more like those of Ma in many 
of the smaller American Cedzd@e than in the long-faced or 
“ Dog-headed ” Baboons (Cyzocephalt) of the Old World. 

The vomer is generally longer, and of less vertical extent, 
than in Man. The turbinals have much the same general 
characters, their relative situation of course varying with 
the elongation, or otherwise, of the nasal passages. ‘The os 
planum of the ethmoturbinals always forms part of the inner 
wall of the orbit, having the same relations as in Man. 

The pterygoid plate of the alisphenoid is usually largely 
developed, and generally projects considerably backwards 
beyond the pterygoid bone (which is narrow, and has a very 
distinct hamular process), and there is always a wide and 
deep fossa between them. 

‘The premaxilla is always distinct on the facial surface, 
and the suture between it and the maxilla is only obliterated 
in aged specimens. It generally extends upwards on the 
side of the anterior nares, so far as to meet the nasal and 
completely exclude the maxilla from taking any part in the 
boundary of this opening. 


140 THE SKULL. [cHar. 


The lachrymal foramen is never situated externally to the 
orbit, although, in the lower forms, it may be close upon 
the margin. 

As in Man the postorbital process of the frontal meets 
the orbital process of the malar so as completely to encircle 
the outer side of the orbit ; and an extension backwards and 
inwards of these bones joining the alisphenoid divides the 
orbit from the temporal fossa. 

The nasal bones vary much in length and breadth, but 
they present the peculiarity throughout the order of a great 
tendency to ankylose together in the middle line, even at a 
comparatively early age. 

In all the smaller and middle-sized onlays the general 
surface of the calvaria is oval and smooth, but in the larger 
Baboons and Orangs there are well-marked supraorbital, 
sagittal, and occipital ridges. These attain their greatest 
development in the adult male Gorilla, where they com- 
pletely mask the original form of the cranium. Their size, 

in this sex, appears to increase with age; while in the oldest 
~ females, on the other hand, they are but slightly apparent. 

The paroccipital process is always rudimentary, as in 
Man. 

The squamosal in the higher forms is developed much as in 
Man; but in the lower forms it is more reduced, and takes a 
smaller share in the formation of the side wall of the cranium. 
It generally comes in contact, at its upper anterior angle, 
with the frontal, but not in the Orang or in the Cede, in 
which animals the union of the parietal and the alisphenoid 
separates the frontal from the squamosal, as is usually the 
case with Man. ‘The glenoid surface is flatter than in Man, 
and there is a well-marked postglenoid process. 

The zygoma is usually narrow, horizontal, and slightly 
arched outwards. 


x.] PRIMATES, 141 


The periotic generally resembles that of Man, and the 
-mastoid portion is conspicuous on the outer side of the 
skull between the squamosal and the exoccipital ; but its 
surface is smooth and rounded, without any distinct mas- 
toid process. 

In all the Old World species, the tympanic forms an elon- 
gated inferior wall to the external auditory meatus, which 
has consequently a considerable bony tube; but in all the 
American Monkeys this bone retains more or less its primi- 
tive annular condition, and the cavity of the tympanum is 
close to the external wall of the cranium. ‘This character 
alone will readily serve to determine to which of the two 
great divisions of Monkeys a skull may belong. 

No auditory bulla is developed in any of the Old World 
Monkeys, but in all the Ceb:sde and Hapalide the inferior 
surface of the ankylosed periotic and tympanic is much 
swollen. 

The carotid canal is always very conspicuous, entering the 
under surface of the periotic near its hinder border. There 
is often a glenoid foramen, but never an alisphenoid canal. 

The foramen rotundum perforates the alisphenoid, but 
the foramen ovale is usually a notch on its posterior border, 
completed by the periotic behind. 

The mandible presents the same general characters as 
that of Man, but the horizontal portion of the ramus 
is usually more elongated, and the anterior border slopes 
upwards and forwards, there being a complete absence of 
mental protuberance. The condyle is extended trans- 
versely, the coronoid process well developed and recurved. 
The posterior or ascending portion of the ramus is broad 
and flat; the angle well developed, square, or more or 
less rounded, but without any special pointed process as in 
the Dog. 


142° TILE SIGOLL. [CHAP. 


In the Howling Monkeys (A/yceres) the hinder or ascend- 
ing portion of the ramus is remarkable for its extent, both 
vertically and antero-posteriorly, corresponding to a certain 
extent with the extraordinary development of the vocal 
organs, which it partially covers and protects. 

The Szmiina are remarkable in never, or very rarely, 
having an ossified stylohyal; but on looking closely at the 
base of the periotic, immediately to the anterior and inner 
side of the stylomastoid foramen, a very small depression, 
in which there is sometimes a minute ossified tympano-hyal, 
can generally be seen. To this the ligament representing 
the stylohyal is attached. 

In very few of the Old World Monkeys is there any 
ossification in the anterior hyoid arch (see Fig. 50); but in 
some Cercopitheci a short, bony, ceratohyal is found. This 
occurs also in the American Monkeys (Fig. 51), with occa- 
sionally the addition of a second piece (epihyal). 

The thyrohyals are always well-developed, long, narrow, 
nearly straight, and somewhat flattened. 


Fic. 50.—Inferior surface of hyoid bones Fic. 51.-—Inferior su face of hyoid bones 
of Baboon (Cynocephalus porcarius). of an American Monkey (Lagothria 
bh basibyal; ¢/# thyrohyal. humboldiii). th thyrohyal; ch cerato- 


hyal ; e/ epihyal. 


The basihyal varies muchir form. In the anthropoid Apes 
it is broad transversely; but in nearly all the other Monkeys 
its antero-posterior extent exceeds its breadth, owing to a 


x.] PRIMATES. 143 


great development from the posterior border. It is generally 
convex: below, and concave above and behind, forming a 
considerable cavity, in which the median laryngeal air-sac 
is lodged. This condition is enormously exaggerated in 
the American Howling Monkey (AZyeertes), where the basi- 
hyal is transformed into an immense subglobular, thin- 
walled, bony capsule, with a large orifice posteriorly, 
by which the laryngeal air-sac enters, and having the 
straight narrow thyrohyals attached on each side. In this 
genus there are no ossifications in the anterior arch. 


While, in nearly all the characters in which the skull 
of Man differs from that of the Dog, the Szmzna agree 
with the former ; the Zemurina, on the other hand, mcre 
resemble the lower type. . 

In the Common Lemur the general proportions of face 
to cerebral cavity, and the inclination of the occipital and 
olfactory planes of the cranium, are quite dog-like. The 
orbits, although completely surrounded behind by the 
junction of the postorbital processes of the frontal and the 
malar, are yet perfectly continuous with the temporal fossa 
beneath this bony bar; that extension inwards of the 
frontal and malar to meet the alisphenoid, and thus form a 
posterior external wall of the orbit, so characteristic of 
Man and all Monkeys, being absent. The lachrymal fora- 
men, situated on the facial part of the bone, is altogether 
external to the margin of the orbit. The os planum of 
the ethmo-turbinal does not enter into the inner wall of 
the orbit, but is shut out from it by the maxilla, as in 
most inferior mammals. The inferior surface of the tym- 
panic is developed into a large rounded bulla. The hyoid 
apparatus much resembles that of the Dog, having ‘the 
stylohyal, epihyal, and ceratohyal all distinctly ossified in 


144 THE SROLL. [CHAP. 


the anterior arch, and the basihyal in the form of a narrow 
transverse bar. 

Some of the Zemurina have much shorter faces than the 
common species, though still possessing all the essential 
characters of the group. Among these, Zars¢us is remark- 
able for the extraordinary size of the orbits, which are so 
expanded that their margins form prominent, thin, bony 
rings, and the interorbital part of the skull is reduced to 
an exceedingly delicate septum. The orbit is also partially 
separated from the temporal fossa as in the Szmzzna. 


The general characteristics of the skull of the CARNIVORA 
have been described, as seen inthe Dog. The more obvious 
modifications from this type relate to the comparative 
length and compression or width of the facial portion, the 
strength and curve of the zygomatic arch, and the extent to 
which the various ridges and processes for the attachment 
of muscles are developed. Thus the Cats have short and 
round skuils, with wide zygomatic arches; and in the Bears 
(especially the Polar Bear, Ursus maritimus) the whole 
skull is elongated, and the nasal cavities are greatly enlarged 
as compared with the brain-case, and the maxillo-turbinal 
bones are correspondingly developed. 

But there are certain other modifications of the cranial 
bones, which, being less obviously adaptive to functional 
purposes, and being constantly associated with structural 
modifications in other parts of the body, are of considerable 
value in classifying the members of the group. Of these 
the most important are related to the form and structure of 
the auditory bulla, and the surrounding parts of the base of 
the cranium. 

In the Bears, the auditory bulla is comparatively little 
inflated. It consists of a single bone (tympanic), readily 


x.] CARNIVORA. 145 


detached from the cranium in-skulls of young animals. Its 
form is more or less triangular, being broad and nearly 
straight at the inner edge, and produced outwards into 
a considerably elongated floor of the external auditory 
meatus. Its greatest prominence is along the inner border; 
from this it gradually slopes away towards the meatus. The 
entrance of the carotid canal is a considerable circular 
foramen, near the hinder part of the inner edge of the bulla. 
In old animals it is partly concealed by the prominent lip of 
the basioccipital, which abuts against the inner edge of the 


Fic. 52.—Section of the left auditory bulla and surrounding bones of a Bear (Ursus 
Jerox). Sq squamosal; 7 tympanic; SO hasioccipital ; a external auditory 
meatus ; ¢ tympanic ring ; e Eustachian canal ; Cav carotid canal. (From Proc. 
Zool. Soc 1869.) 


bulla ; and by the growth of this, and the paroccipital pro- 

cess, it becomes almost included in the deep fossa leading 

to the foramen lacerum posterius. When a section is made 

through the auditory bulla (see Fig. 52) it is seen to be a 

simple thin-walled bony capsule, imperfect above, where it 
i 


146 PH SROLL: [CHAP. 


fits on to the petrosal and squamosal bones, and prolonged 
externally into the much thickened spout-like floor of the 
meatus externus. At the inner extremity of this floor is a 
freely projecting oval lip (¢), which gives attachment to the 
membrana tympani, and which is the original and first ossified 
ring-like portion of the tympanic bone. In the front of the 
floor of the bulla is the groove for the Eustachian canal (e) ; 
between this and the inferior part of the tympanic ring, 
a low and thin ndge of bone with a concave free margin 
rises from the floor of the cavity. This is the only 
indication of any septum or division of the cavity of the 
bulla. 

Behind the bulla, the prominent and tuberous paroccipital 
process projects downwards, outwards and_ backwards, 
standing quite off from the bulla, and only connected with 
it by a low -laterally compressed ridge. Between the 
paroccipital process and the occipital condyle is a smooth 
concave surface, the front of which is excavated into a deep 
notch, the posterior boundary of the foramen lacerum 
posterius, between which and the condyle is situated the 
condylar foramen, which transmits the hypoglossal nerve. 
At the outside of the bulla, just behind the external auditory 
meatus, the mastoid process is distinct and prominent, and 
widely separated from the paroccipital. There is a very 
conspicuous glenoid foramen situated just behind the post- 
glenoid process of the squamosal. 

All the Orside, Procyonide, and Musteide agree with 
the true Bears in the general characters of this region of 
the skull ;- for even when (as in some of the smaller species) 
the auditory bulla is considerably dilated, it always has its 
greatest prominence near the middle of the inner border, and 
gradually slopes away from this point to a prolonged floor of 
the auditory meatus; and though there are often trabeculz 


x.] CARNIVORA. 147 


or partial septa passing mostly transversely across the lower’ 
part,! there is no distinct and definite septum dividing it 
into a separate outer and inner chamber. In all cases, on 
looking into the external auditory meatus (in the dried 
skull when the membrana tympani is removed) the oppo- 
site wall of the bulla can be seen ; or if a probe is. passed 
into the meatus, no obstacle will prevent its touching the 
inner wall. 


Fic. 53.—Section of the left auditory bulla of the ‘Viger (Felis tiyris). Sg squa- 
mosal; P¢ periotic; SO basioccipital; a external auditory meatus ; oc the outer 
chamber ; zc the inner chamber : s the septum; * the aperture of communication 
between the chambers. (From Proc. Zool. Soc. 1869.) 


In the Tiger, which may be taken as a type of the Fede, 
the auditory bulla is very prominent, rounded and smooth 
on the surface, rather longer from before backwards than 
transversely, its greatest prominence being rather to the 
inner side of the centre. ‘The lower lip of the external 
auditory meatus is extremely short; the meatus, in fact, 


1 Especially developed in the Weasels (AZuste/a), in which also the 
entire parietes of the bulla are thickened and cancellous. 


lL, 2 


148 THE SHOLL- [CHAP. 


looks like a large hole opening directly into the side of the 
bulla. On looking into this hole, at a very short distance 
(just beyond the tympanic ring), a wall of bone is seen quite 
impeding the view, or the passage of any instrument, into 
the greater part of the bulla. In the section (Fig. 53) it will 
be seen that this wall is a septum (s), which rises from the 
floor of the bulla along its outer side, and divides it almost 
completely into two distinct chambers ; one (oc), outer and 
anterior, is the true tympanic chamber, and contains the 
tympanic membrane and ossicula, and has at its anterior 
extremity the opening of the Eustachian tube (e); while the 
other (zc), internal and posterior, is a simple but much 
larger cavity, having no aperture except a long but very 
narrow fissure (*) left between the hinder part of the top 
of the septum and the promontory of the periotic, which 
fissure expands posteriorly, or rather at its outer end, into a 
triangular space, placed just over the fenestra rotunda, so 
that the opening of this fenestra is partly in the outer and 
partly in the inner chamber of the bulla. This chamber is 
formed by a simple capsule of very thin but dense bone, 
deficient only at a small oval space in the roof, where the 
periotic projects into and fills up the gap, except such 
portion of it as is left to form the aperture of communica- 
tion with the outer chamber. 

Not only are these two chambers thus distinct, but they 
are originally developed in a totally different manner. At 
birth the only ossification in the whole structure is the in- 
complete ring of bone supporting the membrana tympani, 
and developed originally in fibrous tissue. Ossification 
extends from this, so as to complete the outer chamber, 
and the very limited lip of the meatus auditorius externus. 
The inner chamber is formed from a distinct piece of hya- 
line cartilage, which at birth is a narrow slip, pointed at 


| CARNIVORA. 149 


each end, lying between the tympanic ring and the basi- 
occipital, applied closely to the surface of the already 
ossified periotic, and forming no distinct prominence on the 
under surface of the skull.. Soon after birth this increases 
in size, and gradually assumes the bullate form of the wall 
of the inner chamber. In young animals, even some time 
after the ossification of the bulla is complete, the distinc- 
tion between the two parts is clearly seen externally ; not 
only are they marked off by a groove, but the tympanic 
portion has a more opaque appearance than the other. The 
septum is formed by an inversion of the walls of both, 
applied together, and ultimately perfectly fused in Feé/s, 
although remaining permanently distinct in some of the 
Viverride. 

The carotid foramen in the Tiger is only represented by 
a minute groove deep in the recess of the foramen lacerum 
posterius. In the smaller Cats, this groove is more super- 
ficial, but always very minute, and apparently never converted 
into an actual foramen, except by the contiguous wall of the 
basioccipital. 

The paroccipital process is flattened over the back of the 
bulla, being applied closely to the whole of its prominent 
rounded hinder end, and projecting, as a rough tubercle, 
slightly beyond it. From the inner side of this process a 
sharp ridge runs towards the occipital condyle. ‘This forms 
the posterior boundary of a deep fossa, at the bottom of 
which is the foramen lacerum posterius, and in the hinder 
part of which, under cover of the aforesaid ridge, the 
condylar foramen opens. The mastoid process is a 
moderately conspicuous rough projection, not very widely 
separated from the paroccipital. There is no distinct 
glenoid foramen. 

The Viverride agree with the Ae/¢e@ in having the auditory 


150 THE SKULL: [CHAP. 


bulla divided into two cavities by a bony partition, in having 
the paroccipital spread over the hinder surface of the bulla, 
and in having no prolonged external auditory meatus; but 
the bulla is more elongated and compressed, and the inner 
chamber is placed altogether behind the outer or true 
tympanic chamber. | 

In the Hyeena this region of the skull much resembles the 
same part in the Cats, but the bulla is simple and undivided. 
In the Dogs there is a partial septum, and otherwise the 
characters are intermediate between the two extremes of the 
Bears on one side, and the Cats on the other.! 

In nearly all the Carnivora the hyoidean apparatus is con- 
structed on the same plan as described in the Dog, having a 
narrow, transversely elongated, curved basihyal, either round, 
or compressed from above downwards, a nearly straight 
compressed thyrohyal, not ankylosed with the basihyal, and 
a well-ossified anterior cornu, composed of three distinct 
pieces of subequal length. In the Lion, Tiger, and Leopard, 
however, the anterior arch is imperfectly ossified, the dif 
ferent bones being small, and connected together by long 
, ligamentous intervals ; but in the Puma, Cheetah, Lynx, and 
Cat, the bones are large, and in close relation with each 
other. 

In the Seals the brain-cavity is very broad, round, and 
rather depressed. The orbits are large, and the interorbital 
portion of the skull greatly compressed. The olfactory 
chambers of the nasal cavities are consequently very narrow, 
and the ethmeturbinals little developed; but in front of the 
orbits the cavities widen, and the maxilloturbinals are very 


1 For the various modifications of the structure of this part of the 
skull in the different genera of the order, see ‘‘On the Value of the 
Characters of the Base of the Cranium in the Classification of the Order 
Carnivora.” (Proc. Zool. Soc., 1869, p. 5.) 


<a CARNIVORA. I5I 


large and complex. The mesethmoid is of considerable 
vertical extent, and its ossified portion, which is extensive, 
terminates anteriorly in a straight vertical line. In some 
forms, as Cystophora, this ossification extends in front of the 
nasals. The hyoid resembles that of the typical Carnivora, 
all the elements being well ossified and distinct. The 
Otaritde, or Eared Seals, also called Sea Bears or Sea 
Lions, are intermediate in most of their cranial characters 
between the true Seals and the Bears. 


The skulls of the animals composing the Order INSEc- 
TIVORA present great variations. 

In some of the higher forms, as Galeopithecus, Tupaza, 
Macroscelides, and Rhynchocyon, the cranium much resembles 
that of the Zemurina, having a considerable and vaulted 
cerebral cavity, large orbits, nearly vertical occipital plane, 
large olfactory fosse, a well-developed zygomatic arch 
sending up a postorbital process to meet a corresponding 
one from the frontal so as either partially or completely to 
encircle the orbit behind, and tympanics ankylosed with 
the other cranial bones, dilated into a bulla, and _pro- 
duced externally into a tubular auditory meatus. The 
face is generally elongated, and narrow anteriorly, but in 
Galeopithecus it is broad and depressed. 

In the Macroscelide, or Elephant Shrews, the auditory 
meatus is very large, the tympanic bulla much inflated, and 
there are sometimes also very large mastoid bulle. 

In Zupaia, the malar has a large, oval, longitudinal per- 
foration. There are also in this genus, as in some of the 
other Insectivora, vacuities in the palate, arising from defects 
of ossification, like those found in many Marsupials. 

In the remaining Insectivora the cranial cavity is of small 
relative size. The orbit and temporal fossa are completely 


152 DAE SKULL: [CHAP. 


continuous, and there is often not even a trace of a post- 
orbital process to the frontal or malar. 

In the Lrinaceide (Hedgehogs) and the Centetide the 
tympanic is a mere ring unankylosed to the surrounding 
bones, but a kind of bulla is formed by a lamella projecting 
from the basisphenoid to join its inner and inferior edge. 

In Lrinaceus and Gymnura the zygomatic arch is com- 
plete, but slender, and formed chiefly by the processes of the 
maxilla and squamosal, which meet each other: the malar 
being a small splint-ike bone attached to the outer and 
under side of the middle of the arch. In the Centetzde the 
malar is entirely absent, and, as the zygomatic processes of 
both maxilla and squamosal are very short, there is no bony 
arch. Centetes (the Tenrec) has a remarkably elongated 
and narrow skull (both cranium and face partaking of the 
same character), with very prominent occipital and sagittal 
crests. Both in this genus and in Lynaceus (the Hedge- 
hog) the mesopterygoid fossa at the base of the skull is 
very deep, and ends posteriorly in a hemispherical depression 
in the basisphenoid, between the wing-like processes which 
abut against the inner wall of the tympanic. Both parocci- 
pital and mastoid processes are also well-developed. 

The Moles (Za/pzde) have an elongated and depressed 
cranium, broad posteriorly, and gradually narrowing to the 
muzzle. The occiput slopes upwards and forwards, the 
supraoccipital being greatly developed. The zygomatic 
arches are complete, but very slender, and show no dis- 
tinct malar bones. ‘There are no postorbital or paroccipital 
processes. A lamelliform expansion of the upper edge of 
the periotic (f/erotic, Parker) forms part of the lateral wall of 
the cranium, as in the Echidna. The tympanic is united 
with the other bones of the cranium to form a flattened 
bulla, produced into a short meatus with a small external 


x.] _ INSECTIVORA. - 153 


opening. There isa small “ prenasal” ossicle in the anterior 
extremity of the mesethmoid cartilage, as in the Pig. 

In the Cape Golden Mole (CArysochloris) the cranium is 
conical, very broad and rounded behind, and pointed in 
front. There are no postorbital processes. The zygoma is 
complete, and tolerably strong. The tympanics ankylose 
with the skull, and form a completely ossified bulla. 

In the Shrews (Sovicéde) the cranium is broad behind and 
tapering forwards. The facial portion is long and narrow. 
The occiput slopes much forwards. There is no zygoma 
and no postorbital process. The postglenoid process of the 
squamosal is remarkably large. The tympanic is ring-like, 
and there is a large unossified space on each side of the 
base of the skull. 

The mandible in the Insectivora has generally an elon- 
gated and rather narrow horizontal portion, above which 
the transversely extended condyle is but slightly elevated, 
and there are well developed coronoid and angular processes ; 
the latter is remarkably long and slender in the Shrews. 

The hyoid is formed generally like that of the Carnivora, 
with three complete extracranial ossificatiors in the anterior 
arch, a transversely extended basihyal, and tolerably long, 
stout, flattened thyrohyals, sometimes ankylosed with the 
basihyal. 


Order CuHrIROPTERA.—In the large Frugivorous Bats 
(Pteropus), the cranium is generally elongated, the cerebral 
cavity large, oval, arched above, and contracted in front ; 
its walls formed mainly by the greatly expanded parietals, 
both supraoccipital and frontals being small. In old indi- 
viduals of some species there are well-marked sagittal and 
occipital crests. The base of the cranium is elongated, flat, 
and thin. ‘The facial part is long and rather compressed. 


154 « VEEN SICOLE: [CHAP. 


The postorbital processes of the frontals are long and 
pointed, and partially define the orbits behind; but there 
is usually no corresponding ascending process from the 
zygomatic arch, which is long and slender, and mainly 
formed by the processes of the maxillary and squamosal, 
the malar being a splint-like bone attached to their under 
and outer surface. The lachrymal foramen is situated outside 
the margin of the orbit. The nasals are long and narrow, 
and often ankylose together in the middle line. The pre- 
maxille are small. The palate is elongated’ backwards ; 
the horizontal plates of the palate bones being large and 
early united in the middle line, without defects of ossifica- 
tion. The pterygoids are small. There is no alisphenoid 
canal. The glenoid fossa is broad and shallow ; the post- 
glenoid process very little developed, and with a venous 
foramen behind it. The tympanics are very slightly con- 
nected with the neighbouring bones, and are consequently 
nearly always lost in macerated skulls. A wedge-shaped 
portion of the mastoid appears on the outside of the skull 
between the squamosal and the exoccipital. The par- 
occipital process is long and rather slender, and directed 
downwards and backwards. ‘The periotic has a large and 
deep fossa for the flocculus on its inner side. 


sh 
an 


i th 
Fic. 54.—Hyoid bones of Frugivorous Bat (Pterofus) from below. 64 basihyal; 
th thyrohyal; s% stylohyal. 

The mandible has a high, broad, recurved coronoid pro- 
cess, a transversely extended condyle, and flattened rounded 
angle, without a distinct process, 

The hyoid (Fig. 54) has a narrow, transversely extended 


x.] CHIROPTERA. 155 


basibyal, with which the elongated, laterally compressed and 
curved thyrohyals are commonly ankylosed. ‘The anterior 
cornu contains three slender ossifications of nearly equal 
length. 

The Insectivorous Bats generally have the skull shorter 
and broader than the Preropz. The cranial cavity in many 
species 1s almost globular, with thin smooth walls, though 
sometimes sagittal and occipital crests are developed. The 
occipital foramen is very large. The zygoma is slender. 
Postorbital processes are sometimes well developed, but 
more often small and rudimentary. The face is usually 
short and broad, in some (as AZormops) bent upwards on the 
cranium in a remarkable manner, so that the plane of the 
palate is nearly perpendicular to the basicranial axis. The 
premaxille are generally small, sometimes not meeting in 
the middle line, and sometimes (as in A/egadevrma) altogether 
wanting. The tympanics are annular, not ankylosed to the 
surrounding bones, nor prolonged into a bony canal ex- 
ternally, though often developing a partial bulla on their 
inner side. 

The mandible has a distinct angular process. 


Order RopENTIA.—In the Rodentia the cerebral cavity is 
generally elongated, depressed, somewhat broad behind and 
narrow anteriorly. The occipital plane is more or less 
vertical; the cerebellar fossa altogether behind the cerebral, 
and the tentorial plane, or division between these fossz, 
approaching the vertical. The anterior part of the cerebral 
fossa is contracted ; the olfactory fossa is of moderate size, 
and situated directly in front of the cerebral. 

The nasal cavities are very large, and both sets of 
turbinals well developed, including an upper or nasoturbinal 
lamella. The olfactory chambers attain their maximum of 


‘ 


156 LITE SPOIL. [CHAP. 


development in some of the Porcupines (/Z7ystvzx), where 
nearly all the bones of the upper part of the cranium are 
expanded by great air sinuses formed within their walls. In 
the Hare, and some others, the two optic foramina in the 
orbitosphenoids are confluent ; and in consequence, in the 
dried ‘skull, there is a direct aperture of communication 
between the orbits above the craniofacial axis. 

The supraoccipital is more or less vertical, and does 
not extend far on to the upper surface of the cranium. 
There is often a distinct interparietal. There are generally 
moderately developed paroccipital processes, which in the 
Capybara (/ydrocherus) are of great length, curving for- 
wards and compressed laterally. They are also very large 
in the Coypu (AZyepotamus). 

The parietals are moderate orsmall. ‘The frontals, except 
in the Squirrels, Marmots, and Hares, have little more than 
a rudiment of a postorbital process, and there is never any 
marked corresponding process arising from the zygoma, so 
that the orbit is perfectly continuous with the temporal fossa. 
The latter is always very small. 

In a very remarkable East African genus, Lophiomys, a 
broad bony lamella extends from the upper part of the 
parietal outwards and downwards to join a similar ascending 
plate from the malar, and sc forming an arched covering 
to the temporal fossa, an arrangement unknown in any 
other mammal, but recalling that met with in the tortoises. 
The whole of the superior surface of the cranial, bones of 
this animal are covered with miliary granulations, disposed 
with perfect regularity and symmetry.’ 

The nasals are both long and wide, and generally extend 
so far forwards as to make the anterior nares quite terminal 
and vertical, or even with a downward inclination. In 


1 See A. Milne-Edwards, Nouv. Archiv. du Muséum, ii. 1867. 


X.] RODENTIA. 157 


fTystrix their development is enormous, but this is chiefly 
owing to their breadth and backward extension over the 
great nasal chambers and air sinuses. They are narrowest 
in Bathyergus and its allies. 

The premaxillz are large, and lodge the great curved 
incisor teeth,! and always send a narrow prolongation back- 
wards by the side of the nasals to join the frontals. 

In the larger number of Rodents there is a great vacuity 
in the anterior or maxillary root of the zygoma of varying 
size and form, apparently an enormous dilatation of the © 
_ infraorbital foramen, and through which a portion of the 
masseter muscle passes (see Fig. 55). It is sometimes as 
large as the orbit itself, with which it communicates freely 
posteriorly, underneath a vertical bar, formed by the 
maxilla in front, and by the lachrymal and malar behind. 
Its inferior boundary is a slender zygoma-like horizontal 
bar, formed by the maxilla alone. In the Rats it is a 
vertical fissure dilated superiorly. In the Viscacha (Lagos- 
tomus), the true infraorbital foramen is separated from the 
large antorbital vacuity by a thin ascending bony lamella. 
In Castor, Lepus, Bathyergus, Sciurus, Arctomys, ana some 
others, the infraorbital foramen is of the usual size. 

In the Hares, the facial surface of the maxilla is curiously 
reticulated. 

The zygoma is present in all, of various degrees of thick- 
ness, but always either straight or more or less curved 
downwards, and usually not much arched outwards.’ Its 
anterior and posterior roots are formed by the maxilla 
and squamosal respectively, the malar intervening. In 
many cases the last-named bone extends backwards, applied 


1 These teeth, though first developed in the .gum covering the pre- 
maxilla, have their roots, when fuily developed, in the maxilla. This 
does not invalidate their determination as incisors. 


158 TILE SILL [CHAP. 


to the under surface of the zygomatic process of the 
squamosal to form the outer side of the glenoid articular 
surface. In the spotted Cavy (Celogenys), the zygoma has 
an enormous vertical expansion, with a rugose or pitted outer 
surface, and a large fossa in the inner side of the maxillary 
portion, with which the cavity of the mouth communicates 
in the recent state. 

The lachrymal bone usually presents both orbital and 
facial surfaces, but the orifice of the canal (lachrymal 
foramen) is always well within the margin of the orbit. In 
the Beaver, and many others, the facial portion is reduced 
to a mere tubercle, and in the Hare the lachrymal is entirely 
within the orbit. 

The palate of the Rodents is usually narrow. In the long 
space intervening between the incisor and molar teeth, it 
has no definite lateral margins, but rounds off insensibly 
on to the sides of the face. In this region the anterior 
palatine foramina form very conspicuous longitudinal slits, of 
specially large size in the Hares. ‘The portion of the palate 
situated between the molar teeth is often very narrow 
anteriorly, and ends posteriorly in a thickened excavated 
border. In the Hare it is reduced to a short transverse 
bridge, extending across the middle line between the pre- 
molar teeth. In the Capybara and Guinea Pig the alveolar 
border of the maxilla is very long, and presents the remark- 
able peculiarity of extending backwards beneath the orbit 
to unite with the squamosal at a level with the anterior 
border of the glenoid fossa. It thus forms the outer border 
of a large conical cavity, opening posteriorly, bounded on 
the inner side by the pterygoids, above by the alisphenoids, 
and below by the palatines. 

The pterygoids are always simple subquadrate lamellee, 
early ankylosed with the basisphenoids, often sending a 


xii] RODENTTA. 159 


well-marked hamular process backwards, which unites with 
the auditory bulla in Ayst7x, Lagostomus, Bathyergus, &c. 
There are usually well-marked pterygoid fossz, and the sides 
of the alisphenoids are often perforated by an alisphenoid 
canal. In /ystrzx the hamular process is slightly bullate. 
The squamosal forms a considerable part of the outside 
wall of the cranium, but in consequence of the large size of 
the united tympano-periotic, the root of the zygomatic 
process is thrown very forward on the side of the skull, 
and the posterior part of the body of the squamosal which 
unites with the occipital is reduced to a long, rather narrow 
strip, interposed between the parietal and periotic. When 
the mastoid bulle are greatly developed, as in Pedetes 


“es AS 
pas 


f RY J 
PONCE fe 
CEPI Be 22 
AS \) wy 
\ BS 5. 


FiG. 55.—Side view of skull of Cape Jumping Hare (Pedezes caffer). 3. Sg squamosal ; 
Pa parietal; AS alisphenoid; “4x frontal; OS orbitosphenoid ; Z lachrymal; 
Na nasal; Pdlx premaxilla; A7x maxilla; Ma malar; 7y tympanic; ExO ex- 
occipital ; Per points to the large supratympanic or mastoid bulla. 


(see Fig. 55), this does not reach as far backwards as the 
occipital, and is a slender curved process, which clasps the 
outside of the bulla, and appears to hold it in its place. 


The glenoid fossa is situated on the under side of the 
posterior root of the zygoma. In its most typical form (as 


160 TE ISICLL, [CHAP. 


in the Capybara, Viscacha, Aguti, Paca, &c.) it is narrow 
and concave transversely, with prominent inner and outer 
edges, the latter being often formed, as before mentioned, 
partly by the hinder end of the malar. In the Beaver the 
glenoid fossa has considerable breadth. In the Porcupines, 
Marmots, Squirrels, Rats, &c., no raised inner margin is 
developed, and the fossa passes insensibly into the side of 
the skull wall. In the Hare it is a transversely oval hollow, 
with a prominent rounded anterior margin. 

The tympanic is ankylosed to the periotic, but not to the 
squamosal ; it generally develops a tubular meatus, which in 
the Hare is directed upwards and backwards, in the Beaver 
outwards and forwards. In the Porcupines, as well as in 
most of the smaller Rodents, the meatus is short. In the 
Capybara it is fissured below. 

There is always a considerable tympanic bulla, which is 
often supplemented by a bulla developed above the tym- 
panic cavity, apparently in the periotic. In some genera 
(Fedetes, Dipus, Chinchilla) this attains an enormous size 
(see Fig. 55, Per), and forms a rounded prominence on the 
posterior -external angle of the skull, interposed between 
the squamosal, parietal, and occipital. Usually, the mastoid 
portion of the periotic only appears on the surface for a 
small space in front of the exoccipital. In the Beaver, it 
forms a conspicuous angular process. 

The periotic is never ankylosed with any of the bones 
of the cranium, other than the tympanic. On its inner 
surface the floccular fossa is nearly always wide and deep, 
but it is absent, or nearly so, in the Capybara, Paca, and 
Porcupine. ‘The place of attachment of the hyoid arch is 
an inconspicuous depression in the usual situation, and the 
tympanohyal is never distinct. This is in relation with the 
rudimentary condition of the anterior cornu of the hyo:d. 


x.] RODENTIA. 161 


In the mandible, the symphysial portion is narrow, curving 
upwards, and rounded laterally, with a single large alveolus 
on each side. The coronoid process is never large, and is 
often rudimentary or absent, in relation to the small develop- 
ment of the temporal fossa and muscle; while the portion 
adjacent to the angle is greatly developed, showing marked 
masseteric and pterygoid fossa, and often with its lower 
edge expanded laterally, or slightly incurved. The angle is 
rounded in the Hares, but it is more often produced into a 
long backward process, more or less pointed and upturned. 
The condyle is considerably elevated, with a rounded 
articular surface, usually longer from before backwards than 
from side to side. 

The hyoid has a transversely extended basihyal and a 
straight compressed rod-like thyrohyal, often ankylosed with 
the basihyal. The anterior arch is long, but mostly liga- 
mentous, the ossification being usually confined to the lower 
part (cerato- and epi-hyals). In the Hares, the basihyal is 
deep from above downwards, and compressed, keeled, or 
pointed in front. 


vi 


CHAP PER OX. 


THE SKULL IN THE UNGULATA, HYRACOIDEA AND 
PROBOSCIDEA. 


Order UncuLata. Sub-order /ertssodactyla.—In the 
Horse the whole skull is greatly elongated, chiefly in con- 
sequence of the immense size of the face as compared with 
the hinder or true cranial portion. The basal line of the 
skull from the lower border of the foramen magnum to the 
incisor border of the palate is very nearly straight. The 
occipital and ethmoid planes are nearly perpendicular to 
this line, the latter inclining slightly forwards. The ten- 
torial plane, strongly marked by inward projecting ridges of 
bone, slopes obliquely backwards at an angle of 45°. The 
cerebral fossa is a smooth and regular oval, broad and 
rounded in front, and with no distinct division into 
anterior and posterior portions. The olfactory fossa is 
short, but deep from above downwards. ‘The pituitary fossa 
is very shallow, and there are no distinct clinoid processes. 
The alisphenoid is very obliquely perforated by the foramen 
rotundum, but the foramen ovale is confluent with the large 
foramen lacerum medium behind. There are considerable 
frontal and sphenoidal air sinuses, but the former do not 
extend any great distance over the brain-cavity. 

In front of the cerebral cavity, the great tubular nasal 
cavities are provided with well-developed turbinal bones, 


CHAP. XI. ] UNGULATA. 163 


J 


and are roofed over by very large nasals, broad behind, and 
ending in front in a narrow decurved point. The opening 
of the anterior nares is prolonged backwards on each side 
of the face between the nasals and the elongated slender 
premaxillz. The latter expand in front, and are curved 
downwards to form the semicircular alveolar border which 
supports the large incisor teeth. 

The orbit is rather small in proportion to the size of the 
whole skull, but very distinctly marked, being completely 
surrrounded by a strong ring of bone with prominent 
edges. The lachrymal occupies a considerable space on 
the flat surface of the cheek in front of the orbit, and 
below it the malar does the same. The latter sends a 
horizontal or slightly ascending process backwards below 
the orbit, to join the under surface of the zygomatic 
process of the squamosal, which is remarkably large, 
and instead of ending, as usual, behind the orbit, runs 
forwards to join the greatly developed postorbital pro- 
cess of the frontal, and even forms part of the posterior 
and inferior boundary of the orbit—a very exceptional 
arrangement (see Fig. 56). 

The palate is very narrow in the interval between the 
incisor and molar teeth, in which are situated the large 
anterior palatine foramina. Between the molar teeth it 
is broader, but it does not extend further back than the 
penultimate molar and ends in a rounded excavated border. 
It is mainly formed by the maxillz, as the palatines are 
very narrow. The pterygoids are delicate slender slips of 
bone attached to the hinder border of the palatines, and sup- 
ported externally by, and generally ankylosed to, the rough 
pterygoid plates of the alisphenoid, with no pterygoid fossa 
between. They slope very obliquely forwards, and end in 
curved, compressed, hamular processes. There is a distinct 

M 2 


164 THE SSKOULT: [CHAP. 


alisphenoid canal for the passage of the internal maxillary 
artery. 

The base of the cranium is long and narrow. ‘The 
glenoid surface for the articulation of the mandible is 
greatly extended transversely, concave from side to side, 
convex from before backwards in front, and hollow behind, 
and is bounded posteriorly, at its inner part, by a prominent 
postglenoid process (Fig. 56, Ag). 


Fic. 50.—Side view of the posterior part of the skull of a Horse, }. /#*% frontal (the 
line points to the postorbital process); Sg squamosal; Pa parietal; SO supra- 
occipital; ZxO exoccipital : oc occipital condyle ; Af paroccipital process ; Per 
mastoid portion of periotic ; Az post-tympanic process of squamosal ; 72 tympano- 
hyal; 7y tympanic; Z¢ postglenoid process of squamosal ; As alisphenoid (the 
line points to the plate of the bone which bridges over the alisphenoid canal); Ma 
malar. 

The squamosal (Sg) enters considerably into the forma- 
tion of the temporal fossa, and besides sending the zygo- 
matic process forwards, it sends down behind the meatus 
auditorius a post-tympanic process (/¢), which aids to 
hold in place the otherwise loose tympano-periotic bone. 


Behind this the exoccipital gives off a very long paroccipital 


process (//). 


ei | UNGULATA. 165 


The periotic and tympanic are ankylosed together, but not 
with the squamosal. The former has a wide but shallow 
floccular fossa on its inner side, and sends backwards a 
considerable ‘‘ pars mastoidea” which appears on the outer 
surface of the skull (er) between the post-tympanic process 
of the squamosal and the exoccipital. The tympanic (7Z7) 
forms a tubular meatus, directed outwards and slightly 
backwards. It is not dilated into a distinct bulla, but ends 
in front in a pointed styliform process. It completely 
embraces the truncated cylindrical tympanohyal (¢%), which 
is of great size, corresponding to the large development of 
the whole anterior arch of the hyoid. 

The stylohyal (Fig. 57, s%) is of great « 
size, compressed, and expanded at the $\ 
upper end, where it sends off a triangular 
posterior process. Below the stylohyal, 
and usually becoming ankylosed with it, 
is a small nodular bone (epihyal), and 
then the arch is completed by a short 
cylindriform ceratohbyal (cz). The basi- 
hyal (02) is rather flattened from above 
downwards, arched with the concavity be- 
hind, and sends forwards a long, median, 
pointed, compressed ‘ glossohyal” pro- 
cess. The thyrohyals (¢#) are compressed 
bars projecting backwards from, and in 
adult animals completely ankylosed to, 
the lateral extremities of the basihyal. 

Each ramus of the mandibie has a 
long, straight, compressed, horizontal 
portion, gradually narrowing towards erg daste Al” 
the symphysis, where it expands laterally 2c csk stylotivals 


tohyal; 4% basihyal : th 
to form with the ankylosed opposite  thyrohyal. 


166 THE SKULL. [cHar. 


ramus the wide semicircular, shallow alveolar border for 
the incisor teeth. The region of the angle is expanded 
and compressed, with a thickened rounded border without 
any process. The condyle is greatly elevated above the 
alveolar border; its articular surface is very wide trans- 
versely, and narrow and convex from before backwards. 
The coronoid process is slender, straight, and inclined 
backwards. 


The skull of the Rhinoceros resembles that of the Horse 
in many essential features, but the occipital region is of 
much greater extent vertically, the form of the cranial cavity 
being concealed externally by large occipito-parietal air- 
cells. There is no postorbital process to the frontal, so. 
that the orbit is not divided from the temporal fossa. 
There is a conspicuous rough antorbital projection on the 
lachrymal bone just in front of the lachrymal forainen. 
The nasals are very large and strong, early ankylosed to- 
gether, arched from before backwards, and pointed ante- 
riorly. The most elevated part of their upper surface is 
roughened, and supports the great median horn which 
characterizes the genus. In some species a posterior rough, 
but less elevated, surface indicates the attachment of a 
second horn. In some of the extinct species the meseth- 
moid cartilage was ossified nearly as far forwards as the ex- 
tremity of the nasals, which is not the case with any existing 
species. The premaxillz are very small, and do not extend 
anteriorly beyond the level of the front end of the nasals. 
The hinder border of the palate is deeply excavated, the 
horizontal plates of the palatines being very narrow. ‘The 
pterygoids are very slender, as in the Horse, but placed more 
vertically. There is a distinct alisphenoid canal. The 
squamosal sends down a very long conical, postglenoid pro- 


54 | UNGULATA. 167 


cess parallel with, and equalling, or sometimes exceeding, 
in length, the paroccipital process. The meatus auditorius 
lies in a deep groove between the postglenoid and the post- 
tympanic processes of the squamosal ; the latter articulates 
with the exoccipital, completely excluding the mastoid from 
the external surface of the skull. 

The tympanic and periotic are ankylosed together, but 
not with the squamosal. They are both very small. The 
under surface of the tympanic is rough, forms no distinct 
bulla, and is much encroached upon posteriorly by the very 
large tympanohyal, which presents a circular, flat, rough, 
inferior surface, half an inch in diameter (in an adult 
Sumatran Rhinoceros). Externally, the tympanic is pro- 
duced into a rough, irregular, inferior wall to the auditory 
meatus. The periotic internally shows the internal auditory 
meatus near its lower part, but no distinct depression for 
the flocculus ; it is prolonged upwards and outwards into 
a small mastoid portion, which, as before said, does not 
appear on the outer surface of the skull. 

The mandible has a very wide condylar articular surface, 
and slender recurved coronoid process, a rounded, somewhat 
incurved angle, a compressed, rather narrow, horizontal por- 
tion, and a shallow depressed symphysis. 

The hyoid is much like that of the Horse, and has a 
glossohyal process from the middle of the basihyal. 


The Tapirs present some singular modifications of the 
same type of skull. 

As in the Rhinoceros, there is no separation between the 
orbit and temporal fossa, but the anterior nares are of 
immense size, and extend backward above the orbits, being 
separated from them only by a thin plate of bone, instead 
of a broad, flat surface, as in the Horse and Rhinoceros. 


168 LAE SKULE, (CHAP, 


The nasal bones are short, broad behind, pointed in front, 
much elevated, and supported by a tolerably well ossified 
mesethmoid, which spreads out laterally at its upper end.! 
The inferior and lateral margins of the great narial apertures 
are entirely formed by the maxilla, which extend up to meet 
the nasals, neither frontals nor premaxillz taking any share 
in them. The ethmoturbinals are small, while the maxillo- 
turbinals, on the other hand, are very extensive, though 
their plications are comparatively simple. A conspicuous 
feature in the upper part of the face is a groove, which 
extends backwards on the side of the dilated hinder end 
of the nasal bone, and curves inwards to form a rounded 
depression over the naso-frontal suture. The form and size 
of this depression vary in different species. It lodges an air 
sinus, with cartilaginous walls extending upwards from the 
nasal chamber. In front of the nares, the rostrum formed 
by the maxillz with the premaxillze in front, is produces 
compressed anteriorly, and curved downwards. 

The base of the cranium resembles generally that of the 
other Perissodactyla. There is an alisphenoid canal, and 
large postglenoid and post-tympanic processes; the latter 
joins the paroccipital process of the exoccipital, but above 
their point of union a narrow slip of the mastoid appears 
on the surface of the skull. The periotic is not ankylosed 
to the squamosal or to the tympanic, which is exceedingly 
rudimentary, forming a small irregular floor to the tympanic 
cavity, with an oval lip for the attachment of the membrana 
tympani, and always becomes detached in macerated skulls. 

The mandible is chiefly noticeable for the great rounded 
incurved posterior projection of the angle. 


1 In one species ( 7: Bazrazz) the ossification of the mesethmoid extends 
far in advance of the nasal bones, and is clasped and supported below 
by ascending plates from the maxillz. 


0d | UNGULATA. 169 


The hyoid has a simple, elongated stylohyal without pos- 
terior process at the upper end, but one other ossification in 
the anterior cornu, and no glossal process to the basibyal. 


Fic. 58.—Longitudinal and vertical section of skull of a Sheep (Ozvzs aries), 4. 
PM-x premaxilla; J77 maxilloturbinal; Ma nasal; HT ethmoturbinal; J7£ 
mesethmoid; #7 frontal; OS orbitosphenoid ; AS alisphenoid; Pa parietal; 
SO supraoccipital ; Per periotic; HxO exoccipital; BO basioccipital; Zs par- 
occipital process; 7 styliform process of tympanic; 4S basisphenoid; PS pre- 
sphenoid;: P# pterygoid; PZ palatine; Vo vomer; JM/a maxilia: cp coronoid 
process ; cd condyle; s symphysis of mandible; sf stylohyal; e epihyal; ch 
ceratohyal ; 64 basihyal ; ¢/ thyrohyal. 


Suborder Artiodactyla.—The skuil of the Sheep, as one 
of the best known and easily procurable examples of. this 


group, may be first described, though in some respects it 
is rather peculiarly modified. 


170 PHE SKOLL. [CHAP. 


On comparing the section of the cranium (Fig. 58) with 
that of the Dog, it will be seen that there isa great difference 
in the relation of the principal elements to each other, inas- 
much as the face is bent downwards on the basicranial axis, 
so that when the latter is horizontal, the upper surface of 
the face looks forwards and the palate backwards. ‘The 
occipital foramen is terminal posteriorly, the tentorial plane 
nearly vertical, so that the cerebellar fossa is altogether 
behind the cerebral, but the plane of the cribriform plate 
is horizontal, and the olfactory fossa altogether beneath the 
anterior portion of the cerebral fossa. 

The occipital region is small and sloping forwards. 
There are long paroccipital processes (ff). In very young 
skulls a distinct interparietal bone is present, but in the 
specimen figured this has coalesced with the parietals 
(SO). The two parietals (fa) unite very early at the 
sagittal suture. The frontals (77) are large, and usually 
(except in some domestic races) develop from their outer 
surface conical, curved, bony processes, cancellous within, 
which are called the “ horn cores,” as they form the internal 
support of the true horns. The nasals (Va) are long and 
pointed in front. The premaxillaz (47x) are slender, with 
a shallow alveolar border, bearing no teeth, and forming the 
anterior and lateral boundaries of large anterior palatine 
foramina. The lachrymals are large, and form a con- 
siderable portion of the side of the face in front of the 
orbit, but the foramen is entirely within the margin. 

The olfactory chamber is large. The turbinals are greatly 
developed ; the upper lamina of the ethmoturbinal or “‘naso- 
turbinal” is distinct, and extends over the scroll-like maxillo- 
turbinal (A77’), but does not ankylose with the nasal. 

The orbit is large, nearly circular, with a complete, 
prominent margin, formed below by the large malar, which 


a. ONGULATA... ~ 171 


extends considerably on the side of the face, and posteriorly 
sends a process upwards to meet the postorbital process of 
the frontal, and is continued backwards to join the zygomatic 

process of the squamosal. 

The palate bones (77) are of moderate extent; their 
horizontal plate is deeply notched posteriorly. The pterygoids 
(Pf) are broad above, but end below in a narrow lamella, 
with a hamular process projecting backwards. The basi- 
occipital (BO), seen from below, is square, with eminences 
for muscular attachments at each of its four angles. The 
basisphenoid (4S) is much contracted laterally. The pos- 
terior clinoid processes are large, and the pituitary fossa 
deep. 

The squamosal is small, and scarcely appears in the interior 
of the skull. The glenoid facet is rather extensive, and 
slightly convex, and there is a postglenoid process and 
foramen. ‘The tympanic is not ankylosed to the periotic; it 
forms a complete tubular external auditory meatus, and a 
considerable, but simple, bulla, narrowing to a sharp-pointed 
process anteriorly (Zy). The periotic (ev) is rather small, 
without any fossa for the flocculus; its mastoid portion 
forms a distinct, narrow, rough surface on the outer side of 
the skull, between the hinder border of the squamosal and 
the exoccipital. The tympanohyal is very large, cylindrical, 
curved, and almost completely embedded in the tympanic, 
between the inferior wall of the meatus and the outer wall 
of the bulla. 

The extracranial portion of the hyoid consists of large 
conipressed stylohyals (sz), with a prominent posterior 
process near the upper end, short but well-ossined epi- 
hyals (ef) and ceratohyals (ch), and a basihyal represented 
by a small rounded nodule of bone, to which the straight 
thyrohyals (#7) are not ankylosed. 


172 T HIG SE OL: [CHAP. 


The mandible has a broad flat condyle (a), a long 
slender coronoid process (cf), a rounded angle, a rather 
slender horizontal portion, contracted and with a sharp 
upper edge in front of the molar teeth, and expanded 
anteriorly for the lodgment of the incisors. 


The Ox agrees generally with the Sheep in its cranial 
characters. The face is bent down on the basicranial axis 
almost in the same manner. The occipital surface is flat, 
and ‘terminates above in a broad transverse ridge, which 
extends between the horn cores. The parietals are ex- 
tremely narrow above, and placed almost entirely behind 
this ridge. They unite very early with the interparietal and 
supraoccipital. The intercornual ridge of the frontals is 
excavated by large air-cells, communicating with those of 
the horn cores, and is especially developed when the horns 
are large. Unlike the parietals, the frontals are of very 
great extent, and have a broad and flattened upper surface. 

The tympanics are compressed and scarcely at all bullate. 
‘They end anteriorly in long compressed styliform processes, 
and become firmly ankylosed with the periotic and squa- 
mosal. The under surface of the meatus auditorius has a 
compressed ridge. The large tympanohyals are entirely em- 
bedded in the tympanic, only the rough lower surface for 
articulation with the stylohyal being exposed. 

The mandible and hyoid are like those of the Sheep, but 
the basihyal is rather more developed, and has a rounded, 
anterior, median projection. 


Many Ruminants (especially among the Cervide) have a 
vacuity of varying extent on the side wall of the face, 
between the frontal, lachrymal, maxillary and nasal bones, 
leading in the macerated skull into the nasal chamber, but 


Xt] UNGULATA. 


173 
closed in the living animal by membrane. - Most of the 
Deer and Antelopes have also a large depression on the 
facial surface of the lachrymal bone, called the suborbital or 
lachrymal fossa, though it has nothing to do with the tears, 
but lodges a glandular fold of the integument, which secretes 
a peculiar unctuous and odorous substance. In most Deer 
the orifice of the lachrymal canal is double, and situated on 
the margin of the orbit, whereas in most of the hollow- 
horned ruminants it is single and placed well within the 
margin. ‘There are however exceptions in both cases. 

In the Deer the axis of the face is nearly in the same 
line with that of the cranium, so that when the basicranial 
axis 1s horizontal the nose is directed forwards instead of 
downwards, as in the Sheep and Ox. The animals of this 
family have no permanent horn cores continuous with the 
cranium and ensheathed by true horns, but have short pro- 
cesses on the frontal bones (fedzcles), from which branching 
antlers of true osseous structure are annually developed 
and shed. ‘These, as a rule, are only present in the males, 
while the Zorns of the Lovide and Antilopide are usually 
common to both sexes. 

Among the Antelopes, the Saiga (Sazga tartarica) is very 
remarkable for the conformation of the upper part of the 
face. ‘The anterior nares extend backwards almost to a 
level with the front edge of the orbits, and have an unusual 
vertical expansion. ‘The nasal bones are aborted or coa- 
lesced with the frontals. The turbinals are very short. 
The lachrymals enter largely into the side walls of the 
anterior nares. The ascending processes of the premaxille 
* are small, and very widely separated from the nasals. In 
the living animal the edges of these greatly expanded narial 
apertures are continued forwards into a truncated, almost 
proboscidiform muzzle without any bony support, giving the 


174 TTL TSO LD. [CHAP. 


contour of the face a totally different appearance from that 
presented by the skull. 

In the Elk (AZes), and a small Abyssinian Antelope 
(Neotragus saltiana), the nasal bones are very much shorter 
than they are in ordinary ruminants. 

The Zylofoda (Camels and Llamas) and the 7ragulina 
differ from most of the /Pecora, and resemble the non- 
ruminating Artiodactyles in having the tympanic bulla 
filled with cancellated bony tissue. ; 


The skull of the Pig shows in section that the axis of the 
face is bent down upon the basicranial axis almost as much 
as in the Sheep, a disposition which increases with age. 
Though the form of the cranial cavity is not very different 
from that of the Sheep, the external appearance of the 
binder part of the skull is greatly changed by the elevated 
and backward sloping occipital crest, formed by the union 
of the supraoccipital (concave from side to side posteriorly) 
and the parietals. ‘The latter have their outer and inner 
surfaces widely separated in the adult Pig by large air-cells, 

The frontal is broad and flat between the orbits, and 
sends out asmall postorbital process, which does not join the 
zygoma. ‘The face is greatly elongated, tapering forwards, 
and compressed laterally. The nasals are long and narrow, 
and the apertures of the nares small and nearly terminal. 
The premaxillz send up long processes on each side of 
the nasals, which, however, do not meet the frontals. The 
lachrymal has a considerable facial portion; and, as in 
other Ungulata, the malar encroaches considerably on the 
face, uniting with the lachrymal. 

At the anterior extremity of the mesethmoid a peculiar 


ossicle (frenasa/) is developed, which strengthens the cartila- 
ginous snout. 


46 INGULATA. 175 


The palate is long and narrow, and extends posteriorly 
beyond the last molar tooth. The pterygoid fossz are well 
marked, being chiefly formed by the well-developed ptery- 
goid plates of the alisphenoid; the true pterygoids are very 
slender. There are very long. slender, compressed par- 
occipital processes, curved forwards. 

The squamosal and tympanic are ankylosed together; the 
floor of the long, narrow, upward-directed auditory meatus 
is formed by the tympanic, wedged in a cleft of the squa- 
mosal, between the hinder edge of the glenoid fossa (there 
being no postglenoid process) and a long descending post- 
tympanic process which articulates with the exoccipital. 

Inferiorly the tympanic is dilated into a very prominent 
bulla, peculiarly elongated vertically, and rather compressed 
from side to side. ‘The interior of this buila is filled with 
cancellous bony tissue. 

The periotic is small and not ankylosed to the oeaeaes or 
squamosal. The mastoid portion is quite rudimentary, being 
merely a short scale-like prolongation upwards and_back- 
wards, lying on the inner surface of the squamosal, and 
making no appearance on the external surface of the skull. 
The tympanohyals are very inconspicuous, being small, and 
situated at the bottom of a deep fossa on the outer and 
posterior side of the tympanic bulla. 

The mandible has a high ascending portion behind, a 
transverse condyle, a very small coronoid process, and a flat 
expanded angle, rounded posteriorly. 

The hyoid of the Pig is very-different from that of most 
other Ungulata. The basihyalis very small. The thyrohyals 
are large, broad and flat, and ankylosed to the basihyal, but 
with their extremities cartilaginous even in old animals. 
There is a well-ossified ceratohyal, not ankylosed with the 
basihyal, but the greater part of the anterior arch is a long 


176 THE SKULL. [CHAP. 


cartilaginous band, with one, or sometimes two, slender 
ossifications near the middle part, representing the stylohyal. 


The skull of the Hippopotamus resembles that of the 
Pig in many essential features, although its external form is 
greatly modified. ‘The brain cavity is very small, and the 
face immensely developed. The orbits project outwards in 
an almost tubular manner, and their margins are nearly, and 
in some cases quite, complete posteriorly. The face is con- 
tracted laterally in front of the orbits, and then expands 
widely into a massive truncated muzzle, which supports the 
great canine and upper incisor teeth. 

The anterior narial orifice is nearly circular; it is bounded 
by the extremities of the narrow, but greatly elongated 
nasals above, and laterally by the prominent, rounded, 
rugged and massive premaxille. At the anterior and lower 
part of the orbit, the lachrymal is dilated into a great thin- 
walled bony capsule, of such delicacy that it is nearly always 
destroyed in the skeletons preserved in museums. ‘This 
opens into the nasal air-passages and has no connection 
with the lachrymal apparatus. A similar but smaller dilata- 
tion exists in many of the Pecora. 

The palate is long and narrow, and extends posteriorly a 
short distance behind the last molar teeth. The internal 
pterygoids end in well-marked stout hamular processes. The 
glenoid surface of the squamosal is very much extended, 
but not bounded externally by a projection from the malar, 
as inthe Pig, and the inner-half of its posterior margin 1s 
produced into a tolerably well-marked postglenoid process. 
The paroccipital process is long and conical, but far less 
conspicuous than in the Pig. The tympanic bulla is pro- 
portionately smaller, and of a trihedral form, ending in an 
antero-inferior pointed process. Its interior is filled with 


X1.] UNGULATA. 177 


cancelli, as in the Pig. As in that animal, there is a long 
narrow meatus auditorius, directed upwards and backwards 
in a fissure between the postglenoid and post-tympanic 
processes of the squamosal, the floor being formed by a 
compressed, ridged prolongation of the tympanic, which 
is at a very early age completely fused with the squamosal. 
The periotic is very small, remains longer distinct, though 
ultimately ankylosing with the conjoined squamoso-tym- 
panic, and has only a rudiment of a mastoid portion, which 
is quite confined to the interior of the cranium. 

The tympanohyal is slender, ankylosed to the back of the 
tympanic, and in the adult skull sunk in a deep fossa, 
between that bone and the exoccipital, which also gives exit 
to the facial nerve. 

The mandible is of immense size and weight. The 
condyles rise very little above the level of thé molar teeth. 
The coronoid process is small and much recurved. ‘The 
angle is greatly expanded and everted, rounded behind, and 
terminating below in a distinct process, projecting down- 
wards and forwards. The horizontal rami are«compressed 
in their middle portion, but widen anteriorly into a very 
broad and massive truncated symphysial portion, which 
supports the huge incisor and canine teeth. 

In the hyoid apparatus, the basi- and thyro-hyals ankylose, 
and are something like those of the Pig. The anterior arch 
consists of three well-ossified pieces of subequal length. 


Order Hyracoipea.—The skull of the Hyrax presents 
many affinities with that of the Perissodactyla, others with 
the Rodentia, and some characters peculiar to itself. 

The cranium is high and truncated behind, the occiput 
nearly vertical, the tentorial and olfactory planes oblique, 
the olfactory fossa rather small. 

N 


178 THE SKULL. , [CHAP. 


There is a small distinct interparietal. The frontal region 
is broad and flat. The zygoma is tolerably strong, and 
formed mainly of the malar, which extends backwards so as 
to form the outer wall of the glenoid fossa, but it is supported 
anteriorly by a strong process from the maxilla. ‘The orbit 
is bounded posteriorly by well-marked postorbital processes 
which sometimes meet, the lower one from the malar, and 
the upper one from the parietal (a very unusual condition). 
The lachrymai is small, and scarcely extends at all on to 
the face, but sends outwards a strong antorbital process (as 
in the Rhinoceros and Elephant). ‘The face is short, and 
compressed laterally. ‘The nasal bones are wide posteriorly, 
and anteriorly are either truncated, or more produced at 
their outer than their inner margins. The premaxillz do 
not send up processes to meet the frontals, as in all 
Rodents. 

The palate is not produced posteriorly beyond the middle 
of the last molar tooth. The palate bones are large. ‘The 
pterygoids very slender. ‘There are well-marked pterygoid 
fossee, and alisphenoid canals. ~The paroccipital processes 
are long and slender. The glenoid fossa is wide transversely, 
and with a considerable postglenoid process. The periotic 
and tympanic are ankylosed together, but usually remain 
distinct from the squamosal. The tympanic forms a 
moderate-sized bulla, and a spout-like floor to the external 
auditory meatus, between the glenoid and _ post-tympanic 
processes of the squamosal. The periotic has a very slight 
floccular depression, and sends backwards no distinct mas- 
toid process. ‘The pituitary fossa is very shallow, without 
clinoid processes. The foramen rotundum and foramen 
ovale are distinct perforations through the alisphenoid. The 
optic foramen pierces the large orbitosphenoid near its 
hinder margin. 


Ll HYVRACOIDEA. 179 


The mandible has a high and exceedingly broad ascending 
portion, its hinder margin being produced far behind the 
condyle, but the angle is rounded, and without any distinct 
process. The condyle is much extended transversely, and 
narrow from before backwards, especially in its inner half, 
for externally it 1s somewhat rounded. The coronoid pro- 
cess is small and recurved. 

The hyoid apparatus of the Hyrax is unlike that of any 
other known Mammal. The basihyal is oval, transversely 
extended and flat, with a small median eminence on its 
anterior border, and an emarginate posterior border, only 
ossified in the centre, and prolonged laterally, without any 
definite segmentation, into broad, flattened, slightly curved 
cartilaginous thyrohyals. Articulated to the anterior and 
external angles of the basihyal are two large, triangular, 
flattened bones (ceratohyals), each with a long process 
projecting forwards and meeting in the middle line, so 
as to enclose (with the anterior margin of the basihyal) a 
triangular space. ‘There is no other cartilage or bone in the 
anterior arch, unless a very minute pyramidal bone, described 
by Brandt as articulating with the mastoid process of the 
skull, represents the stylohyal.' 


Order Proposcipka.—The skull of the only existing 
animals of this order, the Elephants, presents many very 
remarkable features. As the brain-case increases but little 
in size during growth, and as the exterior wall of the skull 
is required to be of great superficial extent to support the 
trunk and the huge and ponderous incisor teeth or tusks, and 
to afford space for the attachment of muscles of sufficient 
size and strength to wield the skull thus heavily weighted, 


1 **Mem. de l’Acad. Imp. de St.-Pétersbourg,” VII* Série, tome xiy. 
No. 2, p. 68. 1869. 
N 2 


180 LAE SHROLL. [CHAP. 


an extraordinary development of air-cells takes place in the 
cancellous tissue between the outer and inner surface walls or 
“tables ” of nearly all the bones of the cranium, separating 
them in some cases as much as twelve inches apart (see Fig. 
60), These cells are not only formed in the walls of the 
cranium proper, but are also largely developed in the nasal 
bone and upper part of the premaxilla and maxilla, the 
bones forming the palate and the basicranial axis, and even 
extend into the interior of the ossified mesethmoid and the 
vomer. Where two originally distinct bones come in contact 
the cells pass freely from one to the other, and almost all the 
sutures become completely obliterated in old animals. 

The intercellular lamelle in the great mass which  sur- 
rounds the brain-cavity superiorly and laterally mostly 
radiate from the inner to the outer table, but in the other 
bones their direction is more irregular. Like the similar 
but less developed air-cells in the skulls of many other 
Mammals, they are entirely secondary to the original growth 
of the bones. In the young African Elephant’s skull figured 
(from an animal about six months old, see Fig. 59), their 
formation has scarcely commenced, and as the sutures are 
still quite distinct, and the bones not distorted by these 
cellular dilatations, they are in a much better state for 
studying their connections and characteristics. 

When the basicranial axis 1s placed in a_ horizontal 
position, it will be seen that the foramen magnum is quite 
posterior, and its plane nearly vertical. The cramial cavity 
is elongated and depressed (more so in the ‘African than the 
Indian Elephant), the tentorial plane nearly vertical, so that 
the cerebellar fossa is altogether behind the cerebral fossa. 
The latter is broad behind and contracted laterally in front. 
The olfactory fossa is large, and placed altogether below 
the anterior part of the cerebral fossa, the cribriform plate 


KY, | PROBOSCIDEA. 181 


Fic. 59.—A section of the cranium of a very young African Elephant (E/ephas 
africanus), taken somewhat to the right of the middle line, so that the meseth- 
moid and vomer are removed, }. ‘The letters as in the other figures. 


Fic. 60.—A section of the cranium of a full-grown African Elephant, taken to the left 
of the middle line, and including the vomer (V0), and the mesethmoid (J7£). 
av anterior, and fz posterior narial aperture, y's. 


182 LULL. (GID Le [CHAP. 


being nearly horizontal. The ridge which separates the 
anterior from the posterior division of the cerebral fossa is 
very well marked. The pituitary fossa is very shallow, and 
there are no distinct clinoid processes. The supraoccipital 
(SQ) is high, and inclines greatly forwards; so that the occi- 
pital surface looks upwards as much as backwards. In the 
adult skull (Fig. 60) the lateral parts of the occipital region 
(rounded smoothly off in the young state) are vastly expanded 
and leave between them a deep median depression, with a 
rugged floor, and a partial bony septum at the bottom, into 
which the ligamentum nuche is inserted. The median por- 
tion of the supraoccipital never becomes expanded by air- 
cells. The parietals (72) are very large, and form the greater 
part of the lateral walls of the cranium. ‘The frontals (77) 
are narrow from before backwards, and produced laterally 
into elongate supraorbital processes, which send out small 
postorbital processes, not, however, completely separating 
the small orbit from the large and high temporal fossa. 

The most remarkable feature in the face is the form and 
position of the anterior narial orifice (az). It is wide trans- 
versely, very short from above downwards, placed very high, 
and is directed upwards and forwards, almost as much as in 
the Whalebone Whales. The nasal bones (/Va@) which bound 
it above are very thick, short, broad behind, and conical 
in front, and contain large air-cavities. The inferior and 
lateral margins of the orifice are formed entirely by the pre- 
maxillz (47x), which send processes up to join the nasals 
and frontals. In front of the nares the face is prolonged 
into a somewhat quadrate, depressed, alveolar process, trun- 
cated in front, concave above, rounded laterally, formed by 
the premaxillz above and at the sides, and by the maxille 
below. ‘This contains the roots of the great incisor teeth 
or tusks. 


XI. ] PROBOSCIDEA. 183 


The lachrymal is small, placed almost entirely within 
the margin of the orbit, and ends anteriorly in a projecting 
antorbital process. The zygomatic arch is slender and 
straight, the malar being small, and forming only the middle 
part of the arch, the anterior portion of which is (unlike 
that of all Ungulates) formed by the maxilla. 

The elongated, tubular nasal cavity forms a sigmoid 
curve, being directed (from below) at first forwards, then 
upwards, then forwards. The olfactory chamber is a 
comparatively small fossa in the middle third of its posterior 
wall, filled by the complex ethmoturbinals. The maxillo- 
turbinals are but rudimentary, the narial passage being quite 
free.t The floor of the palate is completed posteriorly by 
well-developed palatines (77). The pterygoid (/*) is slender 
and very early ankylosed with the pterygoid process of the 
alisphenoid, which is greatly expanded, and hollowed in 
front, being spread round the dilated posterior margin of 
the alveolar portion of the maxilla, and aiding to close the 
great alveolar cavity of the hindermost molar tooth. _ 

The squamosal (.S7) forms a considerable part of the cranial 
wall, extending outside the small alisphenoid to meet the 
frontal, and externally sends off a broad post-tympanic pro- 
cess, which meeting (though not uniting with) the hinder bor- 
der of the glenoid fossa in front, bounds the bony external 
auditory meatus, to which the tympanic contributes very 
little. The latter bone is, in the young specimen, completely 
united with the periotic, but not with the squamosal. In- 
feriorly it forms a large, rounded, but not very prominent 
auditory bulla, deeply notched on its inner side by the 
canal for: the internal carotid artery (cc). , The periotic 
(Per) presents a large surface within the cranium without 


1 The elongated proboscis probably supplies their place functionally 
in warming the inspired air. 


184 THE SKULL. (CHAP. XI. 


any floccular fossa. ‘The mastoid portion is very small, and 
does not appear on the surface of the cranium. ‘There 
are no paroccipital or postglenoid processes. At the bottom 
of a deep fossa between the squamosal, exoccipital, and tym- 
panic, the tympanohyal is distinctly seen, with the stylo- 
mastoid foramen to its outer side. The exoccipitals are 
not perforated by a condylar foramen, neither is the ali- 
sphenoid perforated, but it is grooved in front for the 
foramen rotundum, and behind for the foramen ovale. 

The mandible is of a very peculiar shape. ‘The ascending 
portion of the ramus is high, and terminates in a rather small 
rounded condyle, wider from side to side than from before 
backwards. ‘The posterior border is thick, but rounded off 
gradually into the inferior edge, without any projection at 
the angle. The coronoid process is compressed, and but 
very little elevated. The horizontal portion is very massive 
and rounded to support the great molar teeth; it unites 
with its fellow in front in a narrow, prolonged, spout-like 
symphysis. , 

The stylohyals are forked at their upper extremity, the 
posterior process being greatly developed. They taper 
below to a point which is connected by a long ligament with 
the basihyal. The thyrohyals are long, compressed, and 
ankylosed to the basihyal.! 


1 See A. H. Garrod. . Proc. Zool. $92 1875, p.' 365. 


Oe 
7 


ye 


CHAPTER XIE 
THE SKULL IN THE CETACEA AND THE SIRENIA. 


Order Ceracea.—The animals of this order exhibit some 
remarkable modifications in the characters of the skull. 

I will first select for description that of a young example 
of one of the Odonfoceti or Toothed Whales, the common 
round-headed Dolphin or Glodbicephalus of our coasts. Fig. 
61 represents a vertical median section of this skull. It will 
be seen that the cerebral cavity is of a very unusual shape, 
being short and broad, but extremely high and contracted 
above—in fact, somewhat in the form of a truncated cone, 
with rcunded edges. The bones of the basicranial axis are 
curved upwards at each extremity. They consist of the 
ankylosed basioccipital (4O) and basisphenoid (B.S) sepa- 
rated by a vertical fissure from the presphenoid (PS) and 
mesethmoid (J7£), which are also ankylosed, though their 
original line of separation can still be traced. ‘The pituitary 
fossa scarcely forms a distinct concavity, and the clinoid 
processes are almost obsolete. The mesethmoid is very 
large, and consists of (1) a high and broad vertical plate, 
which closes in the vacuity between the frontals in the 
anterior part of the cerebral cavity, and corresponds io the 
cribriform plate of the ordinary Mammal, though with Lut few 
and small perforations ; (2) an anterior rod-like, somewhat 


186 , LTE SKULL, [CHAP. 


compressed, pointed prolongation from the lower part of this 
plate, which extends forwards in the groove of the vomer 
(Vo) almost to the extremity of the rostrum, and which in 
great part remains permanently cartilaginous. ‘This corre- 
sponds with the septal cartilage of the nose of other Mam- 
mals, although owing to the altered, position of the nares it 
has here little relation with these passages. 

The cranial cavity is formed chiefly of the cerebral fossa, 
the cerebellar fossa being relatively small, and the olfactory 
fossa entirely wanting. 

The optic nerve passes out through a deep notch, some- 
times a foramen, in the hinder border of the orbitosphenoid. 
The alisphenoid is not perforated, the foramen rotundum 
being confluent with the large sphenoidal fissure, and the 
foramen ovale with a large infundibuliform opening between 
the alisphenoid, parietal, exoccipital, basioccipital, and basi- 
sphenoid, in the bottom of which is seen the inner surface 
of the periotic (Per), which in the Cetacea makes no projec- 
tion into the cerebral cavity. The anterior part of this 
Opening corresponds to the foramen lacerum medium with 
the foramen ovale, the hinder part to the foramen lacerum 
posterius.t The squamosal (.S7) appears in the outer bound- 
ary for a very small space, between the parietal and the 
exoccipital. The condylar foramen pierces the exoccipital, 
near its anterior edge. The large or nearly circular carotid 
canal has a peculiar position, passing through the basisphe- 
noid, near its middle, in a direction from below upwards, 
forwards, and inwards. 

The bones forming the walls of the cranial cavity are dis- 
posed in a very remarkable manner. The occipital surface 

1 In the adult of the same species, the foramen ovale is separated 


from the large opening common to the seventh and eighth pair of nerves 
by a streng bony partition formed by the ossified tentorium cerebelli. 


XII. CETACEA: 187 


is of great size, and slopes upwards and forwards. ‘The 
foramen magnum is large, and looks directly backwards ; its 
lower lateral margins are bounded by large oval condyles; 
which meet in the middle line below, and are formed by 


Fic. —A section of the skull of a young Dolphin (Globicephalus melas), +. PATx 
BERS Oe ix max lla; WE ossified portion of tne mesethmoid; az anterior 
nares; Na nasal; /P interparietal ; #7 frontal ; Pa parietai ; SO supraoccipital ; 
£xO exoccipital; BO basioccioital ; Sg squamosal ; Per periotic ; AS alisphenoid ; 
PS presphenoid; /P¢ pterygoid; fz posterior nares; PZ palatine; Vo vomer; 
s symphysis of mandible ; zZ inferior dental canal ; cf coronoid process ; ca con- 
dyle ; @angle; sf stylohyal, 4% bas.hyal ; ¢# thyrobyat. 


the exoccipitals, with a small portion of the basioccipital. 
Above the foramen, the immense supraoccipital (SQ), with 
which an interparietal (77) is ankylosed, extends forwards 
beyond the vertex, to be wedged in between the frontals, 
completely excluding the parietals from the upper region of 


188 THE SKOULE. [CHAP. 


the cranium. These latter (a) form the greater part of the 
sides of the narrow high temporal fossz, and are ankylosed 
with the supraoccipital above, although the different elements 
of the occipital are still distinct. The frontals (77) are broad 
from side to side, being prolonged outwards into the arched 
supraorbital plates, but are almost entirely covered by lamel- 
liform extensions of the maxilla, which leave but a thin 
strip of the frontals visible on the external surface of the 
cranium. The temporal fossa is bounded below and in 
front by a stout postorbital process of the frontal, very nearly 
meeting the broad zygomatic process of the squamosal. The 
orbit is elongated from before backwards ; at its anterior 
extremity is a rounded antorbital prominence, formed by 
the junction of the maxille, frontal and malar; below, it is 
bounded by a long and very slender styliform zygomatic 
process of the malar, which arises from near the anterior and 
inner angle of the’body of the bone, and passes backwards, 
slightly curved downwards, to articulate with the extremity 
of the zygomatic process of the squamosal. There is no 
distinct lachrymal bone, or canal. 

The special modification of the bones of the face has 
relation chiefly to the peculiar position of the nasal passages, 
which, instead of passing forwards above the roof of the 
mouth to the anterior extremity of the face, are directed 
upwards and somewhat backwards towards the vertex of the 
cranium; the external narial orifices being situated quite on 
the top of the head, the part which first appears above the 
surface of the water when the animal rises for the purpose of 
respiration. The whole nasal cavities are small, and they are 
(as far as concerns their bony walls) simple canals, entirely 
destitute of turbinals. Though their direction is in the main 
vertical, they are not straight, but curve round the anterior 
end of the brain cavity, both upper and lower orifices (az and 


Be] CETACEA. 189 


fu) being directed somewhat backwards. They are com- 
pressed before backwards above, but wider and more round 
below. The nasal bones (/Va), instead of being lamelliform, 
and roofing over the nasal passages, are reduced to nodular 
masses, lying in depressions in the frontals, but forming as 
usual the hinder boundary of the anterior narial openings. 

In front of these openings, the face stretches out into 
an elongated, depressed, pointed beak, or vostrim, formed 
by the premaxillee and maxillz surrounding the vomer and 
mesethmoid cartilage. ‘The premaxillee send prolongations 
upwards to form the iateral boundaries of the narial orifice, 
and it is remarkable that these are not quite symmetrical, 
that of the left side being the shortest. ‘The orifice itself, 
moreover, is rather inclined towards the left. Between the 
antorbital process of the maxilla and its rostral prolongation — 
is a deep notch, the “antorbital notch.” The upper surface 
of the face, near this notch, has several very large foramina 
for the transmission of branches of the fifth nerve. 

The elongated, pointed, and convex palate is formed 
chiefly by the maxille (Fig. 62, 17x), the premaxillz (PJ/x) 
only appearing for a short space near the apex. Behind 
the-maxillz, the palatines (7/7) are somewhat wide laterally, 
but towards the middle line form an exceedingly narrow 
strip, Inserted between the maxillz and the pterygoids (/%) ; 
the latter are greatly developed ; besides forming the outer 
wall of the posterior nares, each sends a lamella inwards, 
which nearly (in most Dolphins, completely) meets its fellow 
in the middle line, and so prolongs the bony palate back- 
wards. This process, moreover, is reflected outwards again 
from its inner or lower edge, and, joining with a projecting 

plate from the palatine, encloses a large cavity, open only 
behind, which contains the post-palatine air sinus. The 
vomer (Vo) is of great size, extends forwards nearly to the 


190 THE SICOLEL. [CHAP. 


apex of the rostrum, embracing the mesethmoid cartilage, 
and posteriorly reaches for a considerable distance beneath 


PME 


Fic. 62.—Under surface of the cranium of a young Dolphin (Globicephalus melas), 1. 
LO basioccipital ; Ax2O exoccipital ; Pex posterior (mastoid) process of periotic ; 
7y tympanic; Sg squamosal; AS alisphenoid ; OS orbitosphenoid; 7/7 zygo- 
matic process of malar; #7 supraorbital process of frontal; 47a body of malar ; 
Pt pterygoid; PZ palatine; A/a maxilla: PMx premaxilla; Vo vomer; gf 
glenoid fossa of squamosal ; ¢g¢ deep groove on squamosal for meatus auditorius 
externus, leading to tympanic cavity ; cf condylar foramen. 


the basisphenoid. It forms as usual the inner wall of the 
posterior narial apertures. Behind these apertures the base 


elt] GETACEA. | IQI 


of the skull is flat in the middle line, but with prominent 
lateral elevations formed by the basioccipital, continuing 
the pterygoid ridge backwards. The glenoid fossa (gf) is 
a shallow, oval facet, on the inner and under surface of the 
zygomatic process of the squamosal. 

The periotic region of the skull differs much from that 
of most Mammals. On the side of the base of the cranium 
is a large recess, bounded below by the prominent edge of 
the basioccipital on the inner side, by a projecting edge of 
the exoccipital (paroccipital process) behind, by the base 
of the zygomatic process of the squamosal externally, and 
by a long curved process from the same bone in front, and 
communicating with the cranial cavity above by an irregular 
opening between the exoccipital and the alisphenoid. In 
this recess lies a bone of singular shape which, having only 
a ligamentous connection with the surrounding bones, is 
easily separated from the rest of the cranium in maceration, 
and is hence often wanting in specimens in museums. This 
is the united tympanic and periotic, ankylosed in the adult, 
but in young specimens still separable into its two com- 
ponent parts. : 

The tympanic (7Zy) is a hollow, bullate bone, broad, 
rounded and bilobate behind, and pointed in front. It 
is Open above, the hinder part being however in relation 
with the periotic. ‘Through the anterior spout-like end the 
Eustachian canal passes. At the upper border of the outer 
side, rather behind the middle, is an irregular or somewhat 
crescentic opening, bounded in front by a prominent lip; 
this is the meatus auditorius externus, closed in the living 
animal by the membrana tympani. 

The periotic is a rounded, very dense bone, characterized 
as usual by having on its inner or cerebral side the large 
meatus auditorius internus, and on the surface turned 


192 THE SKOLL. [CHAP. 


towards the tympanic cavity the fenestra ovalis and rotunda. 
These two bones are separated along their inner margin by a 
narrow fissure, the “ tympano-periotic fissure ;” but they are 
united externally in front of the external meatus auditorius, 
and more firmly posteriorly, where a tongue-shaped process . 
(Per) projects backwards and outwards, fitting into a groove 
formed by the junction of the squamosal and exoccipital, 
and which is the principal point of attachment of the 
tympano-periotic to the rest of the skull. This process 
resembles in its relations the mastoid of ordinary Mammals, 
but in young Cetaceans it may be seen to be composed of 
two nearly equal parts, in close apposition with each, the 
inferior being derived from the tympanic, and the superior 
from the periotic, so that the latter alone can represent the 
“ pars mastoidea” of other Mammals. 

The mandible (Fig. 61) consists of a pair of nearly straight 
compressed rami, wide behind and gradually narrowing to 
the symphysis (s), where they usually become ankylosed in 
adult animals. The condylar articular surface (cd) is small, 
and looks almost directly backwards, being placed on the 
hinder edge of the ramus. The coronoid process (cf) is 
quite rudimentary. The angle is square and flat. The 
entrance to the dental foramen on the inner side is ex- 
tremely wide and infundibuliform. 

The ossified portion of the hyoid in the true Dolphins 
consists of a large subcylindrical, shghtly curved stylohyal on 
each side, and a flattened crescentic median bone, composed 
of the ankylosed basihyal and thyrohyals. The stylohyal is 
connected. above by a slender cartilaginous rod to a small 
ossified tympanohyal, which becomes ankylosed to the 
periotic in the usual situation, close to the stylomastoid 
foramen; it has aiso a strong ligamentous attachment to 
the prominent rough paroccipital process of the exoccipital, 


XII. ] CETACEA. 193 


Between the stylohyal and the basihyal are one or two dis- 
tinct short cartilages articulated together by synovial joints, 
one of which occasionally becomes ossified. 

In many of the Delphinide the rostral portion of the skull 
is proportionally more elongated and compressed than in 
the species just described ; notably so in Pontoporia, a South 
American genus. In this animal the mandible has a very 
long symphysial portion, the two rami being parallel and 
ankylosed for more than half their length, and diverging 
only in the posterior portion. 

The Sousou, or //afanista, a Dolphin inhabiting the 
rivers of South Asia, has also a remarkably elongated and 
compressed rostrum and mandible, and the cranial portion 
of the skull presents several structural peculiarities. The 
orbit 1s extremely small, the temporal fossa large, and 
the zygomatic processes of the squamosal are greatly 
developed. From the outer edge of the ascending plates 
of the maxillee, which lie over the frontals, great crests of 
bone, smooth externally, but reticulated and laminated on 
their inner surface, rise upwards, and, curving inwards, nearly 
meet in the middle line, above the upper part of the face. 


The Physeteridz, including the genera Zphius, Hy- 
peroodon, Physeter, and their allies, present several special 
modifications of the skull. The bones of the face and 
cranium, meeting at the vertex, are raised so as to form a 
more or less elevated transverse prominence or crest behind 
the anterior nares, generally curved forwards at its upper 
edge. The bone which corresponds to the malar in other 
Dolphins is usually divided into two, one of which may 
represent the lachrymal. The pterygoid bones are thick, 
produced backwards, meeting in the middle line for a 
considerable space, concave on their outer side, but not 

O 


194 THE SKULL. (CHAP. 


involuted to form an outer wall to the post-palatine air sinus. 
In some of the ZA/izne the rostrum is very dense, the 
anterior prolongation of the mesethmoid being either 
partially or completely ossified, and ankylosed with the 
surrounding bones. 

In Hyperoodon, the crest at the vertex is high and mas- 
sive, being formed by the nasals, the ascending plates of the 
premaxille and maxillz, the frontals and supraoccipital. 
Separated from this crest by a depression, there is on each 
maxilla, at the commencement of the rostral portion of the 
skull, a very thick and high longitudinal ridge. 

An easy transition from this cranium leads to that of 
the great Sperm Whale or Cachalot (PAyseter macrocephalus), 
which of all Mammals is perhaps the most modified from 
the ordinary type. The transverse vertical crest and the 
longitudinal maxillary crests are united, to form the walls 
of a great semicircular basin, surmounting the whole of 
the back part of the cranium, open only above and in 
front. The bones composing this wall are the same as in 
Hyperoodon, but excessively expanded and flattened. The 
rostrum is broad at the base, gradually narrowing to the 
front, and immensely elongated. The great supracranial 
cavity lodges the oily substance which, when cre is 
known as spermaceti. 

The skull of the Cachalot is remarkable for its want of 
symmetry, especially in the region of the anterior narial 
apertures, of which the left is very much larger than the 
right. In consequence of the small increase in the size of 
the brain cavity, compared with that of the external parts of 
the head in these enormous animals, the foramina through 
which the nerves pass out of the lateral parts of the base 
of the skull, are long channels excavated through immense 
bony masses. The petro-tympanic bone, which is scarcely 


XII. ] CETACEA. 195 


larger than that of some of the small Dolphins, is situated 
at the bottom of such a channel, at the distance of fourteen 
inches from the inner wall of the brain cavity. In the 
general principle of their conformation, these bones do not 
differ from those of the ordinary Dolphins, but the tongue- 
shaped backward projection before described is greatly 
elongated and laminated, being composed of a large num- 
ber of distinct thin plates, only held together by their com- 
mon attachment to the tympanic. These fit into grooves 
between the squamosal and exoccipital, their extremities 
appearing on the outer surface of the skull, and they serve 
to attach the petro-tympanic more firmly to the cranium 
than is the case in the other Toothed Whales. 

The hyoid in PAyseter and in the allied genus KXogza is 
remarkable for the great breadth and flatness of the basi- and 
the thyrohyals, which, moreover, do not usually become 
ankylosed, as in most Dolphins. 

The cranium of the Whalebone Whales (suborder A/ysva- 
cocett) never shows that deviation from bilateral symmetry 
. so frequent in the Toothed Whales. The cranial cavity 
has much the same general form, and the bones around are 
disposed in a somewhat similar manner, but the parietals 
meet at the top of the skull, although completely overlaid 
and concealed externally by the great supraoccipital. 

The ariterior nares are not directed upwards and _ back- 
wards as in the Dolphins, but approach more in position to 
those of the ordinary miaammalia, being arched over by the 
frontals, which are of considerable antero-posterior thickness 
at this part (see Fig. €3, #7.), and also by moderately-deve- 
loped nasals (Va), meeting by a flattened surface in the 
middle line. ‘The nares are still near the most elevated part 
of the head, and the premaxille and maxillz, with the 
vomer and mesethmoid cartilage, are produced in front of 

O 2 


196 THE SIGGLT. [CHAP. 


them into a long tapering rostrum, narrow, compressed, and 
much arched in the Right Whales (4alena) ; broader, de- 
pressed, and nearly straight in the Rorquals (alenoftera). 

An essential difference between the Whales and the 
Dolphins is the presence in the former of an olfactory organ, 
of the same type as in other mammals, though in a compara- 
tively rudimentary condition. In the skull of an adult Green- 
land Whale (Aalena mysticetus), the olfactory fossa of the 
cerebral cavity is eight and a half inches in length, scarcely 
more than half an inch high, and one and a half inches 
wide. It runs forward from the anterior part of the floor of 
the cerebral fossa, through the great mass of bone formed by 
the union of the frontal, mesethmoid and presphenoid. In 
front it divides into two compartments, each somewhat oval 
and dilated, with a concave floor, about an inch in extent 
in either direction, perforated with foramina. This floor is 
the cribriform plate. In the hinder wall of the great narial 
passage is a narrow vertical slit, twelve inches in length, 
very near the middle line; this is the opening of the 
olfactory chamber of the nasal cavity, which is bounded 
by the under surface of the cribriform plate above, by the 
flat mesethmoid en the inner side, and has its outer wall 
raised into several longitudinal elevations of very simple 
character, representing the ethmoturbinal bones. 

In the Rorquals (Balenoptera) the olfactory fossa is less 
elongated, the foramina of the cribriform plate larger and 
more numerous, and the ethmoturbinals better developed. 

The supraorbital processes of the frontals are very long 
and narrow in the Right Whales, but broader in the Rorquals; 
they are not covered by plates from the maxillz, as in the 
Dolphins. The orbit is small and completed below by a 
small curved malar, quite different from that of the 
Dolphins. ‘There is a small wedge-shaped lachrymal inter- 


XT: CHTACEA: 197 


posed between the antorbital processes of the frontal and 
maxilla and the malar. 

The palate is long and narrow, with a strong keel or 
ridge in the middle line. The surface on each side, sloping 
upwards and outwards, is perforated by many large foramina 
to permit the passage of blood-vessels and nerves to the 
matrix of the baleen, or ‘‘ whalebone,” which covers it in 
the living animal. It is chiefly formed by the maxilla, 
behind which are large palatines and very small and widely 
separated pterygoids. 


x 
ZA 


EEE eg 
Fee hee 


ng 


Fic. 63.—Section of the skull of a foetal Southern Right Whale (Badena australis), '- 
PMzx premaxilla; Na nasal; #7 frontal; Pa parietal; SO supraoccipital ; OS 
orbitosphenoid ; AS. alisphenoid; L2O exoccipital; Per periotic; BO basi- 
occipital ; Zy tympanic ; BS basisphenoid ; Sg glenoid articular surface of squa- 
mosal; P¢ pterygoid ; PZ palatine; PS presphenoid ; Vo vomer; A/x maxilla ; 
cp coronoid process of mandible; cd condyle ; dg dental groove; zg remains of 
groove which lodged Meckel’s cartilage. No part of the mesethmoid is ossified. 


The zygomatic process of the squamosal is an immense 
trihedral pillar in Bafena, having the large shallow glenoid 
fossa on its under surface removed considerably from the 
middle of the cranium, so as to give sufficient width to the 


198 THE SKULL. [CHAP, 


hinder part of the capacious mouth. The periotic and 
tympanic are formed much on the same principle as in the 
other suborder, and in adult animals are completely excluded 
by a considerable distance from the cranial cavity, owing to 
the thickness of its walls. Instead of the small flattened 
tongue-shaped process projecting backwards from these bones, 
there is a long pyramidal tenon-like process, which fits into 
a groove in the squamosal and appears on the external sur- 
face of the skull like, though more solid than, that of the 
Cachalot. In addition to this another process projects out- 
wards and backwards, and the two together hold the bones 
much more firmly in their place than in the Toothed Whales. 
The tympanohyal is a large conical bony mass, with a 
truncated base, with which the stylohyal is connected, and 
firmly ankylosed by its apex to. the periotic. 

The mandible differs much from that of the Toothed 
Whales. - The two rami of which it is composed are not com- 
pressed and straight, but rounded and arched outwards, and 
never have extensive, flat, opposed symphysial surfaces, but, 
curving towards each other, meet at an angle in front, where 
they are held together by strong bands of fibrous tissue. 

The hyoid arch is formed essentially on the same plan as 
in the other Cetacea. The basihyal has a pair of pro- 
cesses placed side by side on its front edge, to which 
the anterior cornua are attached ; the hinder edge is exca- 
vated. In Balena the thyrohyals are cylindrical, and thicker 
towards their free extremities. In Balenoptera musculus they 
are cylindrical and tapering, in B. rostrata, flat and pointed 
externally. They always ankylose with the basihyal. 


Order SrrENIA.—The animals belonging to this order, 
restricted at the present time to only two genera, which were 
ormerly, but quite erroneously, included among the Cetacea, 


X11. ] STRENTA. 199 


7 


have skulls constructed on a very peculiar type, though with 
some affinities both to the Ungulata and the Proboscideia. 
Many of the special modifications are adaptations to their 


Fic. 64.—Section of the skull ot an African Manati (J7anatus senegalensis), { 
PMzx premaxilla; Vo vomer; M2 maxilla; /7 frontal; £7 ethmoturbinal : 
ME mesethmoid; Fr frontal ; Pa parietal; Sg squamosal ; SO supraoccipital ; 
£xO exoccipital; Per periotic; BO basioccipital; 7y tympanic; AS alisphenoid ; 
BS basisphenoid ; PS presphenoid; P¢ pterygoid; P/ palatine; 7x maxilla ; 
cp coronoid process of mandible; ca condyle; @ angle; s symphysis; s/ stylo- 
hyal ; 64 basihyal ; #4 thyrohyal. 


aquatic mode of life, and it is in these alone that they 
present any resemblances to the Cetacea. 
The skull of the African Manati (AZanatus senegalensis), 


200 TE SIGUELL, [CHAP. 


which may be taken as a type of the order, is remarkable 
for the massiveness and density of structure of the bones of 
which it is formed. There are no air sinuses in any part, 
and most of the bones when cut through appear as hard and 
solid as ivory. This character is not pecuhar to the skull, 
but shared with it by the ribs, and other bones, and must 
‘add much to the general specific gravity of this slow-moving 
animal, and aid in keeping it to the bottom of the shallow 
water in which it dwells, while feeding on fuci and other 
aquatic vegetables. 

The cerebral cavity is very different from that of the 
Cetacea, being small as compared with the size of the 
animal, rather elongated and laterally compressed, truncated 
at each end, and with the upper surface flattened. The 
cerebellar fossa is large, and altogether behind the cerebral ; 
the olfactory fossa is distinct, but smal! and narrow, bounded 
on the inner side by a strongly-developed “ crista galli” from 
the mesethmoid. The foramen magnum is of great size ; its 
plane looks backwards and downwards. ‘The supraoccipital 
(SO) is inclined forwards, but does not extend beyond the 
ridge bounding the occipital region ; the roof of the cere- 
bral fossa of the cranial cavity being formed by the parietals 
(Pa). The upper surface*of the skull is very narrow, and 
flat or slightly arched in the longitudinal direction ; its 
sides, which are parallel for a considerable distance, join 
at a right angle the vertical inner wall of the great temporal 
fossa. The squamosal has an extremely massive and 
long zygomatic process, flattened on the outer surface, and 
posteriorly it sends down a strong triangular post-tympanic 
process, articulating with a rough projecting edge of the 
exoccipital. Above this, between the squamosal, supra- 
occipital, and exoccipital, is a considerable vacuity in the 
cranial wall, partly filled by the periotic (Per). The lower 


% 


Lr. | STRE NTA. 201 


vacuity, between the exoccipital and alisphenoid, common 
to all skulls, is of immense extent. 

The frontals (77) are narrow, and run backwards between 
the parietals to the upper part of the cerebral fossa of the 
brain cavity, and forwards a short distance over the nasal 
cavities ; each is produced anteriorly into a long narrow 
process, inclining outwards and downwards, between the 
temporal fossa behind, and the great anterior narial openings 
in front, forming the roof of the orbit. This cavity has a 
very prominent margin, especially below and in front, where 
it is formed by the very largely developed malar. ‘This bone 
sends upwards a conspicuous postorbital process, which 
nearly (in some cases completely) meets that of the frontal, 
and then is continued below the zygomatic process of the 
squamosal as far as the wide shallow glenoid fossa, and 
sends down from its middie a broad flattened process with a 
thickened and rough inferior border. There is a very small 
scalelike and imperforate lachrymal in the usual situation at 
the anterior and inner angle of the orbit. The antorbital 
foramen of the maxilla is very large. 

One of the most peculiar features cf the upper surface of 
the face is derived from the position of the anterior nares, 
which is a further modification of that met with in the Tapirs 
among the Ungulata, and presents some approach to that 
so characteristic of the Cetacea. Taken together they form 
a large lozenge-shaped aperture, which extends backwards 
considerably behind the orbits. Their sides are formed by 
the ascending processes of the premaxillz below, and by 
the supraorbital processes of the frontals above, no trace of 
nasals being found in most skulls, though these bones are 
occasionally present in a most rudimentary condition attached 
to the edge of the frontals, far away from the middle line, 
a condition quite unique among the Mammalia, or only 


202 TEE. SICOLL, [CHAP. 


approached in some of the Dolphins. In the floor of the 
great narial opening Is seen the vomer (Vo), of very delicate 
structure, and posteriorly the ossified portion of the mes- 
ethmoid (AZZ) of considerable vertical extent.» The olfac- 
tory chamber of the nasal cavity is greatly compressed from 
side to side, and contains a series of simple, longitudinally 
placed ethmoturbinals, of which the upper one is very 
much the largest. There are no maxilloturbinals in any 
skulls which I have examined. 

In front of the narial opening the face is prolonged into 
a narrow rostrum, formed by the premaxille, supported 
below and at the sides by the maxille. The under 
surface of this is very rugose, and in life supports a horny 
plate. There is a large, oval, single, median anterior palatine 
foramen. The palate is long and narrow between the two 
parallel rows of numerous molar teeth. It does not extend 
beyond the last of these, and is formed almost entirely by 
the maxille, the horizontal plates of the palate bones 
being very narrow. Behind each row of teeth is a massive 
descending rough process, formed by the union of the 
palatine, pterygoid plate of the alisphenoid, and true 
pterygoid. Posteriorly this has a longitudinal groove 
corresponding to the pterygoid fossa. Behind these the base 
of the skull contracts in width, leaving a large opening on 
each side of the basioccipital, between the alisphenoid in 
front and the exoccipital behind, and only partially filled by 
the tympanic and periotic. | 

The two last-named bones are ankylosed together, but not 
to any of the other bones of the skull, and though freely 
moveable in the dried skull, they are retained in their place 
by the overhanging process of the squamosal. 

The tympanic (7y) consists of 2 large and very solid half- 
ring, with its lower margin considerably thickened and 


x.] ? STRENIA. 203 


produced downwards ; but not forming any bulla, or any 
tubular meatus. It is only attached to the periotic by its 
extremities, and close to the inner side of its posterior 
attachment is a well-marked tympanohyal ankylosed to the 
periotic. 

The periotic (Per) is large, and rounded externally. It 
forms a very considerable part of the inner wall of the 
cranium. Besides the portion containing the organ of hear- 
ing, it has a large solid upper part, of somewhat kidney 
shape, lying in a groove in the squamosal (Sg). This has 
a large anterior prominence, to which the anterior limb 
of the tympanic ring is ankylosed, and a smaller rounded 
posterior projection, corresponding with the mastoid of other 
Mammals, and mentioned before as appearing on the ex- 
ternai surface of the skull, in the vacuity between the supra- 
occipital, exoccipital, and squamosal. 

The foramina at the base of the skull are very few and 
simple, as nearly all the nerves appear to pass out either by 
the rather smali sphenoidal fissure, or by the great confluent 
median and posterior foramina lacera. There is a small 
optic foramen passing through the middle of the orbito- 
sphenoid, but the alisphenoid is imperforate, and even the 
condylar foramen in the exoccipital for the hypoglossal 
nerve, so constant in all Mammals (except the Elephant), is 
represented by a groove (in some instances with a narrow 
bridge across it) on the anterior edge of the bone. ‘There 
is no distinct carotid canal. 

The mandible is exceedingly different from that of the 
Cetacea, and is formed of the same dense heavy bone as the 
rest of the skull. The rami are firmly united by a symphysis 
(s) of moderate extent in front, and diverge widely behind. 
The posterior border is of considerable vertical depth, the 
condyle (cd), with its obliquely placed, oval, convex arti- 


204 THE SKROLT. [CHAP. XII. 


cular surface, being raised high above the horizontal alveolar 
border. Thecoronoid process (cf) is large and directed for- 
wards. The angle (a)is well marked, thickened, and somewhat 
inflexed, but does not form a distinct process. The lower 
border of the ramus is very thick, rounded from side to side, 
and concave from before backwards. The symphysial portion 
is compressed laterally, but its upper surface forms a some- 
what expanded, rugose surface, concave in the middle line, 
to which a horny plate is attached in the living animal. 

In a perfectly adult West Indian Manati (J/. australis), 
in the Leyden Museum, the anterior arch of the hyoid has 
a single, slender, slightly curved bone (stylohyal), three 
inches long, cylindrical at its upper end, and laterally com- 
pressed below, attached above by a broad, short ligament, 
chiefly to the exoccipital, but also to the squamosal and 
tympanic. The basihyal is a broad, flat, reniform plate, and 
the thyrohyals are not ossified. 

In the other existing Sirenian, the Dugong (adicore), from 
the Indian Seas, the skull resembles that of the Manati in 
its essential characters, especially the form of the brain case, 
the condition of the tympano-periotic bones, and the form 
and situation of the anterior nares ; but it differs mainly in 
the great development of the premaxillary bones, which curve 
downwards in front, and lodge large descending tusks. The 
deep, compressed symphysial portion of the mandible is 
bent down in a corresponding manner. ‘The zygoma is less 
massive, the orbit is not closed behind, and the lachryial 
bone is more developed. ‘The nasals are absent or quite 
rudimentary. 


CHAPTER XIT 


THE SKULL IN THE EDENTATA, MARSUPIALIA, AND 
MONOTREMATA. 


Order EpENTAaTA.—The different families of this hetero- 
geneous group present some remarkable variations in their 
cranial characters. 

One of the most extremely modified forms is the Great 
Anteater (Zyrmecophaga jubata, Fig. 65). The whole skull 
is very greatly elongated and narrow, and its upper surface 
smooth and cylindriform. ‘The occipital plane slopes upwards 
and forwards. The parietals are narrow, but the frontals much 
elongated. The olfactory fossa of the cerebral cavity is very 
large ; the cribriform plate greatly expanded, and the ethmo- 
turbinals much developed, and consisting of very numerous, 
delicate lamellae. Anteriorly, the face is produced into a 
very long, tubular rostrum, rounded above and flattened 
below, and with terminal nares. ‘This rostrum is composed 
of the mesethmoid, ossified for more than half its length, 
the vomer, the maxilla, and the long and narrow nasal 
bones ; the premaxille (P4A/x) being extremely short and 
confined to the margin of the anterior nares. There are no 
teeth in either jaw. The zygomatic arch is incomplete, the 
styliform malar (JZa) only articulating with the maxilla in 
front, and not reaching the very short zygomatic process of 
the squamosal (Sz). The lachrymals (Z) are distinct, and 


206 DEM eg Si) GOp By [CHAP. 


-have a large perforation in front of the margin of the orbit. 


| i, 
Pour My 


Fic. 65.—Under-surface of the cranium 
of the Great Anteater (yrmecophaga 
jubata), 4. SO supraoccipital; BO basi- 
occipital; A2O exoccipital; 7y tym- 
panic; P¢ pterygoid; Sg. squamosal ; 
AS alisphenoid ; OS orbitosphenoid ; 
Af malar; Z lachbrymal; P/ palatine; 
Mx maxilla; PM premaxilla. 


There are no postorbital pro- 
cesses to the frontals, or any 
other demarcation between the 
orbits and the temporal fossa. 

The palate is extremely 
elongated, and produced back- 
wards as far as the level of 
the external auditory meatus 
by the meeting in the middle 
line of the largely-developed 
pterygoids (P7). The glenoid 
fossa 1s a shallow oval facet, 
with its long diameter from 
before backwards. 

The periotic, tympanic, and 
squamosal are ankylosed toge- 
ther. A small mastoid portion 
appears on the outer side of 
the skull, forming a roughened 
surface between the squamosal 
and the exoccipital. The tym- 
panic (Zy) is somewhat trian- 
gular in form, slightly bullate, 
and not prolonged into an au- 
ditory meatus. In front of the — 
tympanic cavity, and freely 
communicating with it, is a 
considerable air sinus, formed 
between the pterygoid (7#) and 
the alisphenoid (4.S),and caus- 
ing an oval prominence in the 
side of the palate. 


MIT. | EDENTATA. 207 


In another species of the same genus, JZ, Zamandua, 
there is a second similar but smaller sinus, anterior to this, 
in the side of the palatine bone. 

The mandible is very long and slender, with an exceed- 
ingly short symphysis, no distinct coronoid process, and 
a slightly elevated, elongated, flattened, condylar articular 
surface. 

The anterior cornu of the hyoid is very long and slender. 
Its proximal end is ligamentous, and its distal portion con- 
tains two distinct ossifications. The thyrohyals become 
united by bone to the very narrow basihyal. 

The skull of the little Tree Anteater (Cycdlothurus didac- 
tylus) besides being shorter, and much arched in the longi- 
tudinal direction, differs mainly from that of A/yrmecophaga 
in not having the long canal of the posterior nares closed 
by bone below, as neither the pterygoids nor the greater 
part of the palatines meet in the middle line. The tym- 
panic is more bullate. The mandible has a prominent, 
narrow, recurved coronoid, and a well-developed angular 
process ; it is strongly curved downwards in front. 

In the Armadillos of the restricted genus Dasyfus, in- 
cluding D. sexcinctus, villosus, and minutus, the cranial 
portion of the skull is broad and depressed ; the facial 
portion triangular, pointed in front, and much depressed. 
The anterior narial orifice is small, terminal, and directed 
forwards and downwards. ‘There is a completely ossified 
tympanic bulla, ankylosed with the rest of the skull, per- 
forated on the inner side by the carotid canal, and con- 
tinued externally into an elongated bony meatus auditorius, 
with its aperture directed upwards and backwards. The 
zygoma is complete. The pterygoids are small, and send 
no horizontal plates inwards to complete the bony palate, as 
in the Anteater. The mandible has a well-marked ascending 


208 THE CSKALLT: [CHAP. 


posterior portion, supporting a transversely extended con- 
dyle, and a high, slender coronoid process. 

In all the other genera of Armadillos the tympanic is a 
mere half-ring, loosely connected with the surrounding bones. _ 

The hyoid arch is strongly ossified. The anterior cornu 
consists of three bones. ‘The thyrohyals ankylose with the 
basihyal. 

In the Scaly Anteaters or Pangolins (genus Janis), the 
skull is somewhat in the form of an elongated cone, with 
the small end turned forwards, and very smooth and free from 
crests and ridges. The occipital plane slopes upwards and 
forwards. ‘There is no distinction between the orbit and 
the temporal fossa, which together form a small oval depres- 
sion near the middle of the side of the skull. There are 
short zygomatic processes on the maxilla and the squa- 
mosal, but the arch is incomplete in most species, owing to 
the absence of the malar. There is likewise no distinct 
lachrymal bone. ‘The plane of the anterior narial aperture 
looks forwards and upwards. ‘The premaxilla is produced 
along the side of the nasals towards, but not reaching, the 
frontals. The palate is long and narrow. ‘The Pterygoids 
extend backwards as far as the tympanics, but do not meet 
in the middle line below. The tympanic is ankylosed to 
the surrounding bones, and more or less bullate, but not 
produced into a tubular auditory meatus. ‘The hinder part 
of the squamosal is often dilated with air-cells, forming a 
rounded prominence at the outer posterior angle of the skull. 

The rami of the mandible are edentulous, very slender 
and straight, without any angle or coronoid process. From 
near the anterior extremity of the upper edge a sharp conical 
tooth-like process projects upwards and outwards. The 
condyle is a slightly expanded flattened surface, not raised 
above the level of the rest of the ramus. 


XII. | EDENTATA. 209 


In the Cape Anteater (Orycteropus) the skull is moderately 
elongated and dilated in front of the orbits. The facial por- 
tion is subcylindrical and slightly tapering. The lachrymal 
forms a considerable part of the side of the face. The 
zygoma is complete and slender. ‘There is a small post- 
orbital process. The premaxille are short and widely 
separated from the frontals. The palate ends posteriorly in 
the thickened transverse border of the palatines, and is not 
continued back by the pterygoids. The tympanic is annular, 
and not ankylosed to the surrounding bones. | 

The mandible is slender anteriorly, but rises high pos- 
teriorly, with a slender recurved coronoid, and an ascending 
pointed process on the hinder edge below the condyle; 
which is small, oval, and looks forwards as much as up- 
wards. 

The hyoid arch is completely ossified. The basihyal 
is a thin,,bar, narrow in the middle. The thyrohyals are 
not ankylosed to it. The ceratohyals are thick. There is 
a small (apparently epiphysial) ossification between the epi- 
hyal and the stylohyal. 


The Three-toed Sloths (genus Bradypus) have a high 
compressed skull, and an extremely short face. The cranial 
cavity is oblong, and rather high and compressed. There is no 
fossa on the periotic for the flocculus. The olfactory fossze 
are large. The plane of the occiput is vertical, or sloping 
slightly forwards and upwards. The frontal region is dilated 
with air sinuses. There is a small postorbital process. 
The lachrymal is very small, and the canal is external to 
the margin of the orbit. The malar is attached to the 
frontal, lachrymal, and maxilla in front, curves downwards 
and outwards, and then divides into a descending and a high 
ascending branch; but neither of them join the straight 

P 


210 Opi 5 Uke eG OL by Be [CHAP. 


zygomatic process of the squamosal. ‘The nasals are short 
and wide. The anterior nares are nearly vertical, or rather 
inclining downwards. ‘The premaxillz are exceedingly 
rudimentary, only the palatal portion being present, without 
any ascending process ; they unite with each other across 
the middle line, but not with the maxilla, hence they are 
generally lost in macerated skulls. The palate is narrow, 
especially posteriorly, and not produced behind the molar 
teeth. The pterygoids form large plates with prominent 
rounded borders, compressed in some, and inflated in 
other species. The glenoid fossa is narrow from side to 
side. The tympanic, squamosal, and periotic are ankylosed 
together. The former forms a considerable bulla, but no 
tubular meatus. ‘There are large supratympanic air sinuses 
and a well-marked ossified tympanohyal. 

The mandible has a comparatively high horizontal por- 
tion, rounded in front with a very small median triangular 
process at the upper border. The coronoid process is high 
and slender. The condyle is small; its articular surface is 
convex from side to side, short and nearly straight from before 
backwards. ‘The angle forms a broad compressed posterior 
projection, with a slightly incurved lower border. 

The stylohyals are large, compressed, and curved, with a 
prominent posterior process near their upper end. The 
basihyal is small, and ankylosed with the thyrohyals, so that 
they form together a V-shaped bone. 

The skull of the Two-toed Sloth (Cholepus didactylus), 
though generally similar to the last, presents in some points 
marked deviations from it. Even in aged specimens, in 
which almost all the sutures are obliterated, the tympanic 
is a mere ring, incomplete at the upper margin, and but 
slightly connected with the other bones around. The 
premaxille are more developed, and become ultimately 


tiie] EDENTATA. 211 


ankylosed with the maxillz. The pterygoids are much 
smaller, but sometimes are bullate. 

The upper margin of the mandible is produced anteriorly 
into a spout-like process. The condyle is scarcely above 
the level of the molar teeth, and is wide from side to side. 
The angular projection is smaller and thicker. 

The hyoid (in an old specimen) has a strongly ossified 
anterior arch, consisting of two bones of nearly equal length, 
the proximal one with a stout rounded process projecting 
backwards and outwards from near its upper end. The 
second is bent at a right angle near its lower end, and may 
result from the ossification of two elements. The basi- and 
thyro-hyals are ankylosed to form a wide U-shaped bone. 

_ Order MarsupiALiA.—The skull of the large carnivorous 
Marsupial, the Thylacine (Zhylacinus cynocephalus), resembles 
so closely that of a Dog in its general aspect, that it will be 
well to commence an account of the peculiarities of the 
crania of Marsupials generally by comparing these two 
skulls. 

It will be seen by the section (Fig. 66) that the brain cavity 
of the Thylacine is very much smaller than that of the Dog 
(Fig. 45) in relation to the size of the rest of the cranium, 
or to that of the whole animal, a sign of great inferiority 
of organization. This diminution affects chiefly the cere- 
bral fossa; the cerebellar fossa is nearly equal in size, 
but it is placed more directly behind the cerebral, and is 
not in the least overlapped by it, as in the Dog. The 
occipital plane is vertical, or even inclining forwards above. 
The tentorial plane is nearly horizontal. The olfactory 
fossa, though smaller in vertical extent than that of the Dog, 
is more produced anteriorly. ‘Thus in form, as well as in 
relative size, the cerebral cavity is far more reptilian than 
that of the Dog. ‘The basicranial axis is very straight, and 

P 2 


Ai2 LEE SKROLL. [CHAP. 


is continued forwards in the same line by the basifacial 
axis. The pituitary fossa forms no distinct depression, and 
there are no posterior clinoid processes. The ossified 
portion of the mesethmoid (JZZ£) is extensive, and termi- 
nates anteriorly in a nearly vertical line. The vomer (Vo) 
is very shallow from above downwards. ‘The turbinal 


<Ss 
Nk 


Fic. 66—Section of the skull of the Thylacine (7hylacinys cynocephalus), 4 
M / maxilloturbinal; #7 ethmoturbinal; J7Z ossified portion of mesethmoia ; 
Fr frontal; Pa parietal; SO supraoccipital; £20 exoccipital; Per periotic ; 
BO basioccipital ; Sg squamosal ; AS alisphenoid; BS basisphenoid ; OS orbito- 
svhenoid ; PS presphenvid; Pz pterygoid; P/ palatine ; Yo vomer; J7x maxilla ; 
PMzx premaxilla ; cd condyle of mandible ; @ angular process. 


bones resemble generally in their extent and disdosition 
those of the Dog. 

Externally the conformation of the zygomata, temporal 
fossze, orbits, maxillz, premaxille, and nasals are strikingly 
similar to those of the Dog; but the lachrymal bone of the 
Thylacine is larger both within and without the orbit, and 
it has one perforation within, and either one or two just 


NIir. | MARSUPIALTIA. are 


external to the margin of the orbit. The palate has a pair 
of large oval vacuities between the molar teeth. The ptery- 
goid plates are very thin. The glenoid fossa is rather more 
expanded from before backwards than in the Dog, and the 
malar extends so far back beneath the zygomatic process of 
the squamosal as to form the outer edge of the glenoid cavity. 
The postglenoid and paroccipital processes are developed 
much as in the Dog ; the former has rather greater lateral 
extent. <A great difference is seen in the condition of the 
tympanic, which in the Thylacine is quite rudimentary, forms 
no bulla, and is not ankylosed to the other cranial bones, 
so that in the dried skull it is nearly always detached. On 
the other hand, the hinder part of the alisphenoid is dilated 
into an oval thin-walled capsule, which is connected with 
the front of the tympanic cavity. The periotic is not 
ankylosed to the squamosal, has a very large floccular fossa 
within, and a mastoid portion forming a long, narrow strip 
visible in the outer side of the occipital surface of the skull, 
between the squamosal and the exoccipital, almost exactly 
as in the Dog. The exoccipital is perforated by the con- 
dylar foramen ; but the carotid foramen, instead of passing 
through the inner edge of the tympanic bulla, perforates 
the basisphenoid, passing very obliquely forwards and in- 
wards. The large alisphenoid is pierced by the fora- 
men ovale near its posterior margin, and by the foramen 
rotundum near the front. The orbitosphenoid is very small, 
and not perforated, the optic nerve passing out through the 
sphenoidal fissure. 

The ascending ramus of the mandible is less elevated 
than that of the Dog, the condyle being almost on the same 
level as the molar teeth. The coronoid process has a more 
backward inclination. The masseteric fossa has a powerful, 
externally projecting lower border, and the angular process 


214 THE SKOTL. [CHAP. 


is flattened from above downwards, and inclined consider- 
ably inwards. 

The hyoid (Fig. 67) is constructed on a totally different 
type from that of the Dog. It consists of a small flat 
lozenge-shaped basihyal (0%), surmounted by flattened, 
triangular, imperfectly ossified ceratohyals (c/), partially 
ankylosed to the basihyal, and without any other ossifica- 
tions in the anterior cornua. The thyrohyals (¢/) are tole- 
rably long, flattened bars, meeting in the middle line at their 


Fic. 67.—Upper surface of hyoid of Thylacine (nat. size). 6 basihyal; ch ceratohyal 
(anterior cornu) ; ¢# thyrohyal (posterior cornu). | 


attachment to the basihyal, and with their free, or laryngeal, 
extremities expanded, but still cartilaginous in the perfectly 
adult animal from which the above figure was taken. 


All the other animals of the sub-class which contains 
the single order Marsupialia, however their skulis may 
differ in general appearance from that of the Thylacine, 
agree with it in the following important particulars :— 

1. The brain cavity is small, with the cerebellar fossa 
entirely behind, and the olfactory fossa entirely in front 
of the cerebral fossa. There are, however, degrees in 
this respect, the Kangaroos representing one extreme, with 


XII. ] MARSUPIALIA. 215 


large, more vaulted cerebral fossa, and the Opossums and 
Dasyures the other. 

2. There is no distinct pituitary fossa, or clinoid processes. 

3. The ossification of the mesethmoid is extensive, and 
has an abrupt, nearly vertical, anterior termination. 

4. The nasal bones are large, and the anterior nares more 
or less terminal. 

5. The zygoma is complete, but the orbit has not a 
perfect posterior boundary. 

6. The malar is large, reaches the lachrymal anteriorly, 
and extends posteriorly beneath the zygomatic process of 
the squamosal, to form part of the outer wall of the glenoid 
fossa. 

7. The perforation in the lachrymal is usually upon, and 
frequently external to, the anterior boundary of the orbit. 

8. The ascending processes of the premaxille never 
quite reach the frontals. 

9g. The palate has often, but not always, large vacuities 
near its posterior margin. 

10. The pterygoids are always small and lamelliform. 

tr. The alisphenoids are more or less dilated, and form 
the anterior wall of the tympanic cavity, which is often quite 
open below in the dried skull. It may be noted as a special 
peculiarity in the Kangaroos, that the alisphenoid extends 
backwards beneath the tympanic cavity to join the long 
paroccipital process of the exoccipital. In the larger mem- 
bers of the group it can scarcely be said to form a distinct 
bulla, but in some of the A7ypszprymni (Rat Kangaroos) it is 
immensely expanded. In the Koala (Phascolarctos), the 
alisphenoid bulla is very large, elongated vertically and 
compressed, having a very similar appearance in fact to the 
tympanic bulla of the Pig. 

12. The tympanic is small, simple, and annular in 


216 THE SKULL. [CHAP. 


some ; in others it forms a short external auditory meatus, 
but it is never-ankylosed to any of the other bones of 
the cranium, 

13. The periotic sends backwards a distinct mastoid, 
which appears as a narrow strip of bone of considerable 
vertical extent, between the squamosal and exoccipital, on 
the side of the occipital region of the skull. 

14. There are almost always conspicuous paroccipital 
processes. 

15. The internal carotid artery perforates the basi- 
sphenoid. 

16. The optic foramen is confluent with the sphenoidal 
fissure. 

17. The mandible has (Zavsifes excepted) an inverted 
border to the angle. 


Fic. 68.—Upper surface of hyoid of Fic. 69.—Hyoid of Kangaroo (A/acro- 
Wombat (Phascoloniys latifronus). bh pus). eh epihyal; 6% basihyal; 7¢% 
bas hyal; c# ceratohyal; s% stylohyal; thyrohyal. 
7h thyrohyal. 

18. The hyoid has a small, more or less lozenge-shaped 
basihyal, broad ceratohyals, the remainder of the anterior 
cornu usually unossified, and stout, somewhat compressed 
thyrohyals. 

Order MonorREMATA.—Both the animals of this group 
present very singular modifications of the cranium. 

The cerebral cavity, unlike that of the lower Mar- 


supialia or the Reptiles, with which they have so many 


<1. MONOTREMATA. 217 


structural affinities, is large and hemispherical, flattened 
below and arched above, and about as broad as long. The 
broad cribriform plate of the ethmoid is nearly horizontal. 
The walls are very thin, and smoothly rounded externally, 
and the sutures become completely obliterated in adult 
skulls, so that it is very difficult to trace out the boundaries 
of the component bones. In both species, the broad occi- 
pital region slopes upwards and forwards, and the face is long 
and much depressed, though of very different shape in each. 
In the Echidna (Fig. 70) the squamosal is large and very 
compressed, the zygomatic process arising very far forward ; 
the slender horizontal zygoma being completed by a styliform 
malar, confluent with the maxilla. 
The face is produced into a long E20 \ _ 
<S 
aN 


: Per = < 
oO V = _ Jee 
tapering rostrum, rounded above po . 2e3.. 


4 


from side to side, and concave 
below in the same _ direction. 
The anterior nares form an oval 
opening on the upper surface near oy 
the apex, bounded entirely by the z, 
premaxillz, for the nasals do not 
appear to reach so far forwards. 
The alveolar borders are narrow 
and rounded, without trace of 
teeth. The palate is produced 
backwards, by very large palatine 
bones (77), considerably beyond 
the glenoid fossa. The narial 
canals have very little extent ver- 
tically, but the true olfactory Fic. 70.—Under surface of cranium 


: of Echidna (Echidna hystrix), 3. 

chambers are large, and provided 80 _basioccipital ; ZrO exocci- 
: , : 2 pital; Pex verictic; wz malleus: 
with complex turbinals, which, in sg squamosal; 7y tympanic; P/ 
pterygoid ; P/ palatine ; 17x max- 


accordance with the horizontal ila; 21/2 premaxilla. 


218 Ts EOL Gy i [CHAP. 


position of the cribriform plate, are mostly placed verti- 
cally. 

The pterygcids (/?#) are flattened, horizontal, oval plates, 
attached to the obliquely truncated postero-external extremi- 
ties of the palatines, and form part of the floor and the inner 
wall of the tympanic cavity, an arrangement not met with in 
any other Mammal. The tympanic (7Zj) is a very slender 
ring, incomplete for a small space at the upper and outer 
end, and does not become ankylosed to the periotic. The 
latter (er) is large, has no fossa for the flocculus, sends out 
a large expansion (pterotic), forming a portion of the cranial 
wall between the squamosal, parietal, and occipital, the 
lower and hinder part at least of which corresponds with 
the mastoid portion. 

Each ramus of the mandible is a mere slender style, with- 
out any ascending portion, and with but rudiments of 
coronoid process and angle. The condyle is very small, 
elongated from before backwards, and very narrow. 


Fic. 71.—Lower surface of hyoid of Echidna (Echidna hystrix). eh epihyal ; 
ch ceratohyal ; 6% basihyal ; ¢# thyrohyal. 


The hyoid (Fig. 71) has a well-ossified, transversely 
extended, flattened and arched (with the concavity for- 
wards), basihyal (42). The anterior cornu has only two 
ossifications (cz and eh), apparently the epi- and cerato-hyal, 
as the upper one has a long ligamentous connection with 


XIL.] MONOTREMA TA. 219 


the cranium in the situation of the stylohyal. There are 
broad, flattened, curved thyrohyals (¢/), expanded at their 
laryngeal extremities. 


In the Ornithorhynchus the brain case is smaller than in 
the Echidna, and rather more depressed ; very broad behind, 
and narrowing anteriorly. The olfactory fossa is compara- 
tively small. There are well-marked posterior clinoid pro- 
cesses. ‘The falx cerebri is largely ossified, forming a strong 
median partition to the upper part of the cerebral cavity, 
The zygoma is compressed, and of considerable vertical 
depth, and sends up a well-marked postorbital process ; its 
hinder root arises very far back on the cranium. 

The glenoid fossa is wide and concave transversely. The 
zygomatic process of the maxilla is widened inferiorly into 
an oblong, concave, roughened surface for the attachment of 
the horny plate, which takes the place of the molar teeth. 

The face is broad and much flattened. It runs out 
anteriorly into two diverging processes, each formed by the 
premaxilla, supported by a pointed process of the nasal on 
the inner, and the maxilla on the outer, side. © These bend 
towards each other at their extremities, but do not meet in 
the middle line. They support the partly horny, partly 
membranous beak, which fills up the space between them, 
and extends considerably on each side and infront. There 
is a distinct median ossification in the triangular interval 
between the diverging premaxillary bars, placed in, or in 
front of, the anterior extremity of the mesethmoid cartilage. 
and apparently corresponding to the so-called “ prenasal” 
of the Pig. The infraorbital foramen is very large, cor- 
responding to the large size of the nerves distributed to the 
sensitive sides of the beak. The periotic has a wide and 
deep floccular fossa. 


220 THE SKOLL, [CHAP, XIII. 


The mandible has, rather behind the middle of each 
ramus, an oblong expansion for a horny tooth, corre- 
sponding to that on the maxilla. Behind this it curves 
gradually upwards to the expanded and transversely ex- 
tended articular surface. ‘There is no distinct angle, the 
coronoid process is small and directed much inwards, and 
on the external surface there is a very deep masseteric 
fossa. Anteriorly the rami of the mandible have a very 
slight symphysial connection, in front of which their ex- 
panded, flattened terminations again diverge from each 
other. The apertures for the entrance and for the exit of 


the branches of the inferior dental nerve are remarkably 
large. 


CHAPTER XIV. 
THE SHOULDER GIRDLE. 


HavinG finished the consideration of the axial portions of 
the skeleton, we now turn to the appendicular parts, which 
consist of two pairs of limbs, anterior and posterior. 

The anterior limb is present, and fully developed, in all 
Mammals, being composed of a shoulder girdle and three 
segments belonging to the limb proper, viz. the upper arm 
or brachium, the fore-arm or antibrachium, and the hand or 
manus. | 


The SHOULDER GIRDLE in the large majority of Mammals 
is in a comparatively rudimentary, or rather modified, con- 
dition. Its true structure and its relations to the pelvic 
girdle can only be understood by a reference to its condition 
in the lower vertebrates." 

Each side of the girdle consists primitively of a curved 
rod of cartilage, placed vertically (in the horizontal position 
of the body), the upper or dorsal end being free, the inner 
side lying upon, though not united with, some of the anterior 
thoracic vertebre or ribs, and the inferior or ventral end 
being attached to the side of the presternum. 


1 On this subject see W. K. Parker’s valuable work before cited, and 
also Gegenbaur’s ‘‘ Untersuchungen zur Vergleichenden Anatomie,” 2** 
Heft, 1865. 


222 THE SHOCGCEDER GIRDEE, [ CHAP. 


Near, or rather below, the middle of the outer surface of 
this rod is a more or less cup-shaped depression, the g/enoid 
cavity, to which the head of the humerus, or bone of the 
upper arm, is articulated. The, whole rod 1s separated at 
this spot into two divisions, which ossify from separate 
nuclei. The upper or dorsal division is the scapizla, the 
lower or ventral division is the coracovd. 

In all Mammals above the Ornithodelphia the greater part 
of the coracoid is aborted, but a portion of its upper ex- 
tremity always remains attached to the scapula as a process, 
or sometimes as a most inconspicuous nodule, and occa- 
sionally rudiments of the lower end are found attached to 
the sternum. The scapula, on the other hand, is always 
greatly developed. 

A supplementary bone, developed in a different manner, 
being, at least in the greater part of its extent, ossified from 
membrane,‘ frequently forms an anterior bar, in front of the 
coracoid, passing between the scapula and the anterior end 
of the presternum ; this constitutes the c/avicle. ‘It 1s often 
rudimentary, and very frequently entirely absent, in Mammals. 

Though the scapula may be considered as essentially 
an elongated rod or bar of bone (a condition most nearly 
retained in the Mole), it usually has three projecting plates 
- or ridges arranged around the longitudinal axis, and three 
surfaces or fosse bounded by these, the variations in the 
extent and form of which give rise to the principal diversities 
in the form of this bone in different Mammals. 

In the most usual position of the scapula (see Fig. 72), one 
of these plates (af) projects forwards, this is the prescapula of 
Parker, and its edge constitutes the anterior border (cb) of the 
scapula ; another (f/f) projects backwards, constituting the 


r . . - . : 
1 When it has a cartilaginous basis (as has been described by Gegen- 
baur in Man) this is not a portion of the true primitive shoulder girdle. 


XIv.] ENERAL CHARACTERS. 223 


postscapula, and its edge is the fostertor border (gb) ; a third 
projects outwards, constituting the mesoscapula of Parker, 
called more commonly the sfzwe(s). The first-named border 
(cb) terminates below by joining the coracoid, and hence, to 
avoid the inconvenience of a term which is only expressive 
when the bone is in a particular position, it may be called 
coracou border ; the second (g’) joins the prominent margin 
of the glenoid fossa, and may, for the same reason, be called 


css 


Fig 72.—Right scapula of Dog (Can7s familiaris), 1. ff postscapular fossa; af 
prescapular fossa ; gé glenoid or posterior border; cé coracoid or anterior border ; 
s spine; @ acromion; gc glenoid cavity; ¢ coracoid ; css indicates the position of 
the coraco-scapular suture, obliterated in adult animals by the complete ankylosis 
of the two bones ; ss suprascapular border. 


glenotd border ; the third (s) has a free end, usually more or 
less prolonged into a curved, flattened process, called the 
acromtion (a). 

The flat or concave surfaces or fossze between these pro- 
jecting lamellae are—(1) the prescapular or anterior fossa 
(af ), between the coracoid border and the spine, called, in 
works on human anatomy, “ supraspinous fossa ;” (2) the 


224 THE SHOULDER: GIRDLE, [CHAP. 


postscapular fossa ( pf ), between the glenoid border and the 
spine, also called ‘“infraspinous fossa ;” and (3) the szé- 
scapular fossa, between the coracoid and glenoid borders, 
on the side of the scapula opposite to the spine. 

The greater part of the scapula is ossified by ec¢ostosis (as 
the shaft of a long bone), from a single centre, which is 
placed not far from the middle of the bone ; but this ossifi- 
cation does not extend into a certain portion of the superior 
extremity. This part (swfrascapula) either remains cartila- 
ginous or ‘‘is feebly ossified by one or more endosteal 
patches, or by the creeping upwards of such deposit from 
within the main bone” (Parker). When the spine runs 
out into a projecting acromial process, more or less of its 
terminal portion is ossified separately as an epiphysis. 

The coracoid always ossifies from one or more separate 
centres, and remains for some time suturally connected 
with the scapula, though firmly ankylosing with it by the 
time the animal has attained maturity. Sometimes (as in 
the Sloths) it forms a considerable part of the glenoid fossa ; 
sometimes (as in most Carnivora and Ungulata) it is a mere 
nodule, which becomes blended with the anterior margin of 
the fossa. 

In the Ornithodelphia (see Fig. 80), as in Birds and Rep- 
tiles, the coracoid is largely developed, and articulates with 
the presternum, and there is in addition a plate of bone in 
relation with its anterior edge called efzcoracoid. A small 
plate of cartilage or bone, often found attached to the side 
of the presternum in certain Rodents and Insectivores, is 
considered by Parker as representing the epicoracoid of 
the Ornithodelphia, and by Gegenbaur as the sternal ex- 
tremity of the true coracoid, the middle part of which is 
undeveloped. 

The clavicular arch, when completely developed, extends 


a 


XIv.] GENERAL CHARACTERS. 225 


from the free acromial extremity of the spine of the scapula 
to the anterior extremity of the presternum. 

It consists mainly of an elongated rod of bone, ossified 
usually in fibrous tissue, but at either extremity are certain 
patches of true cartilage, which may become converted into 
bone, or may sometimes degenerate into fibro-cartilage. 
These are thus described and named by Mr. Parker. At 
the scapular extremity of the clavicle, there is often a piece 
of cartilage, considered to be segmented off from the end 
of the mesoscapula, and hence called mesoscapular segment 
(Fig. 73, mss). At the sternal extremity there may be two 
distinct pieces, the one (fc) nearest the clavicle being the 
supposed homologue of a displaced fragment of the pre- 
coracowd of the lower vertebrates. The one (os¢) nearest the 
sternum Is called omosternum by Parker, and episternum by 
Gegenbaur, who considers it homologous with the so-called 
episternum (zv¢erclavicle, Parker) of the Ornithodelphia and 
Lizards. 


Special Characters of the Shoulder Girdle in the Different 
Groups of the Mammata. 


Order Primates. JZan.—In the ordinary erect position of 
the human body, the suprascapular border is directed back- 
wards and inwards, and is commonly called the ‘“ base” or 
“vertebral border” of the scapula ; the glenoid cavity looks 
forwards and outwards; the glenoid border, called “ex- 
ternal” or “ axillary,” looks downwards and rather forwards ; 
and the coracoid border is “superior.” The postscapular 
fossa is much developed, and the suprascapular border is 
long, straight, and forms an acute angle with the glenoid 
border. At the junction of the coracoid border of the 
scapula with the coracoid bone, there is a more or less well- 
marked notch (coraco-scapular notch). The spine is well 


Q 


226 THE SHOULDER IGIRD LE. [CHAP. 


developed, and the acromion large and curved forwards near 
its extremity. 

The coracoid forms a well-marked hook-like process ; it 
contributes a very small part to the glenoid fossa, and unites 
with the scapula about the time of puberty. 

The clavicle (Fig. 73, c/) is a strongly-developed sigmoid 
bone, remarkable for the very early age at which it com- 
mences to ossify, in fact before any other bone of the body. 


Fic. 73.—The human sternum and right shoulder girdle at a very early period of 
development (from an embryo 53 inches long) after Parker, 13. The dotted parts 
are still cartilaginous ; the inner surface of the sternum and clavicle, and outer 
surface of the scapula are represented. ost omosternum, afterwards developed 
into the interarticular fibro-cartilaginous disk ; Zc precoracoid of Parker ; cd shaft 
of the clavicle; #zss mesoscapular segment of Parker; @ acromion; ¢ coracoid ; 
gc glenoid cavity of scapula; ¢6 glenoid border; cé coracoid border; @f anterior, 
or ‘‘supraspinous,” fossa ; 4/ posterior, or ‘‘infraspinous,” fossa; ss suprascapular 
border. 


The outer extremity is, in the young state, tipped with 
cartilage (the mesoscapular segment, Parker, mss), which 
ossifies by extension of bone from the rest of the clavicle. 
It is connected with the acromion by a small oval, flat, 
synovial articulation. ‘The inner end (fc) is also cartilagi- 
nous for some time, but ossifies separately by endostosis, 


XI1V.] . PRIMATES. 227 


forming an epiphysis. This extremity is attached to the 
presternum by synovial articulation, but with a disk-like 
fibro-cartilage (ost) interposed, which, according to Parker, 
is a degeneration of the ‘ omosternal” element. 

In the Gorilla the scapula is very like that of Man. In 
the Chimpanzee it is peculiarly elongated, the suprascapular 
margin being extremely oblique and long, at the expense 
of the greatly reduced coracoid border. The acromion and 
coracoid are largely developed. In the lower Monkeys the 
form of the scapula is quite different, the coracoid and 
glenoid borders being nearly equal, and the suprascapular 
border comparatively short and straight. 

The clavicle is well developed in all, and all its correlates 
are present; the omosternum being generally converted 
during growth into a fibro-cartilaginous intra-articular disk. 

In the various members of the Order INsEcTivora there is 
a great difference in the construction of the shoulder girdle. 

In the Mole (Za/ga) and its immediate allies Sca/ops and 
Condylura, the scapula is extremely high and narrow, and 
appears to be ossified entirely from one centre. ‘The spine 
and acromion are very little developed. The bone commonly 
called clavicle, but which may be a combination of coracoid 
and clavicle, is of remarkable form, being nearly cuboid. It 
is formed primitively of a mass of cartilage, on the anterior 
aspect of which the true (membrane-developed) clavicle is 
engrafted. It articulates inferiorly with the presternum, and 
superiorly with the humerus, and is connected with the 
scapula only by a fibrous band. The two articulations of 
the upper end of the humerus, the one with the scapula, and 
the other with the coraco-clavicle, are separated by a strong 
ligamentous partition. 

In the Cape Golden Mole (Chrysochloris) the condition of 
these parts is quite different. The scapula is long and 

Q2 


228 THE SHOULDIER GIRDLE. .° [CHAP. 


narrow, but flattened. The spine sends a flat process back- 
wards near its middle, and a long slender ‘‘ metacromzal” 
process from its extremity. The clavicle is very long, slender, 
and curved. ‘The ‘“‘ mesoscapular segment” forms a distinct, 
though minute, bone between the clavicle and scapula. 

In the Shrews (Soricide) the scapula (see Fig. 74) is 
also long and narrow, and the slender acromion ends in 
two long diverging processes, of which the anterior (a) 
supports the clavicle and the posterior (ma) is called 
‘‘metacromion.” The mesoscapular segment (mss) is a 


Fic. 74.—Shoulder girdle with upper end of sternum (inner surface) of Shrew (Sovezx), 
after Parker, x 7. fs presternum; s77 first sternal rib; sv? second sternal mb ; 
ec partially ossified “‘ epicoracoid” of Parker, or rudiment of the sternal extremity 
of the coracoid; ost omosternum; Zc rudiment of precoracoid (Parker); cé cla- 
vicle; wzss ossified ‘‘mesoscapular segment;” @ acromion; 7za metacromial 
process ; ¢ coracoid. 


distinct bone. The clavicle (c/) is long and slender. It has 
a small piece of cartilage (fc) attached to its inner end. 
The omosternum (os¢) is cartilaginous or partially ossified, 
and there is a considerable triangular flattened rudiment 
of the inner end of the coracoid (ec) attached to the pre- 
sternum. 

In the other Insectivora the general form of the scapula 


XIV. } CHIROPTERA: 229 


is more normal. In Gaveopithecus the coracoid is greatly 
developed and bifurcated. 

All known members of the order have large clavicles, with 
the exception of Potamogale, a rare aquatic form from 
West Africa. 

In the CHiROPTERA the scapula is large, of an oval form, 
and chiefly formed by the postscapular fossa, the anterior 
fossa being extremely small. ‘The former is divided into 
two or three subfossze by ridges. The spine is short and 
moderately high, with a large and simple acromion. The 
coracoid is long and curved, often simple (as in Preropus) 
sometimes forked (as in Prfestrellus). 

The clavicle is very long and curved. The “ mesoscapular 
segment” on the outer end is soon lost, but the precoracoid 
ossifies separately. The omosternum is reduced to a 
cuneiform fibro-cartilage. A rudiment of the sternal end of 
the coracoid is often present as ‘‘a flat, reniform flap of 
cartilage, feebly ossified by endostosis, wedged in between 
the clavicle and the first rib” (Parker). 

The RopEnt1a offer great diversities in the condition of 
the shoulder girdle. The scapula is generally high and 
narrow, and the acromion long. Sometimes the acromio- 
scapular notch is so deep, that the actual spine only occupies 
a short space near the supra-scapular border, and it is com- 
pleted by a very long and slender acromion (as in the Coypu, 
Myopotamus). There is often a long metacromion, as in the 
Hare ; but in others, as the Beaver, there is no such process. 
The coracoid is always a small blunt hook. 

In a few forms the clavicle is altogether absent, in some it 
is well developed, and various intermediate stages between 
these two extremes are met with. In some species, as the 
Guinea Pig and Rabbit, although no trace of this bone is 
found at birth, it becomes developed at a later period. In 


230 THE SHOULDER GIRDLE. [CHAP. 


both of these it is very short, and is suspended by long 
ligaments between the scapula and the sternum. (See Fig. 
75.) In many species, as in the Porcupines, in which the 
clavicular arch is more complete, the true clavicle is con- 
nected with the presternum by a long cartilaginous omo- 
sternum. In others, as the Beaver, this is replaced by a 
ligamentous band. Rudiments of the sternal end of the 
coracoid are often present, sometimes cartilaginous, some- 
times ossified. 


Fic. 75.—Shoulder girdle, with upper end of sternum (inner surface), of a young 
Rabbit (Lepus cuniculus), after Parker, 3. fs presternum; s? first sternal rib 
ost omosternal cartilage ; fc precoracoid cartilage ; c/ ossified clavicle; mss carti- 
laginous mesoscapular segment ; c coracoid ; @ acromion ; 7za metacromion; a/ 
anterior fossa; 4/ posterior fossa. 


In the Carnivora the anterior and posterior fossz of 
the scapula are nearly equal in area. (See Fig. 72, p. 223.) 
The spine and acromion are fairly developed, the latter 
often with a broad metacromial process. The coracoid is 
much reduced. According to Parker a portion of the 
scapula, near the coracoid border, ossifies from an indepen- 
dent centre. The clavicle is sometimes absent, and when 
present varies much in its development, but is always 
rudimentary and suspended in the muscles, never reaching 


MAENi| CARNIVORA. 2a 


either the acromion or sternum. In the Zed it is slender 
and curved, being longer than in any other members of the 
order. In the Canzde it is very short, and rather broad and 
flat. In most of the Urszde@ it is absent. 

In the Seals both acromion and coracoid are much re- 
duced, but the latter is a distinct bone in young animals, 
and forms a considerable part of the glenoid cavity. The 
whole scapula is much curved backwards, being almost 
sickle-shaped, and the suprascapular epiphysis is very large 
and slowly ossified. 

In the Eared Seals (Ofavia) the scapula has a different 
form, the prescapular fossa being very much larger than the 
posterior, and with a strong vertical ridge, parallel to the spine. 

None of the Pinnipedia have clavicles. 


epee ETE TR 


Fic. 76.—Right scapula of Dolphin (Delphinus tursio), }. ge glenoid cavity ; 
acromion ; c coracoid ; Z/ postscapular fossa ; @/ prescapular fossa. 


Order Ceracra.—In the true Dolphins and nearly all the 
Odontoceti the scapula is usually very broad and flat, or fan- 
shaped. (See Fig. 76.). The prescapular fossa (af) 1s ex- 
tremely reduced’; the acromion (a) is a long flat process, 


232 THE SHOULDER GIRDLE. [cHap. 


with a very narrow base of attachment, projecting for- 
wards ; the coracoid (c¢) is rather long, flattened, and parallel 
with the acromion. 

In the Cachalots (PZyseter) the scapula is formed on the 
same general plan, but is comparatively high and narrow. 
The postscapular fossa is very concave, and the sub- 
scapular fossa convex. The Gangetic Fresh-water Dolphin 
(Platanista) has a flat flabelliform scapula, with the pre- 
scapular fossa entirely absent, and the acromion placed on 
the anterior edge, the spine and the coracoid border having 
coalesced. 

Among the Whalebone Whales, Latenoptera has a broad 
fan-shaped scapula, like that of the true Dolphins, with 
long parallel acromion and coracoid processes, and a supra- 
scapular border which remains permanently in a cartilaginous 
condition. In the Right Whales (a/ena) the scapula is 
more massive and not so broad, and the coracoid is much 
reduced. In A/egaftera the scapula is triangular, and neither 
the coracoid nor the acromion forms a distinct process. 

None of the Cetacea possess clavicles. 

The scapula of the SIRENIA 1s formed on quite a different 
plan, being rather like that of the Seals in shape, narrow, 
and curved backwards. The anterior fossa is nearly as 
large as the posterior. The spine is moderately developed, 
and the slender acromion points downwards. ‘The coracoid 
forms a moderate-sized conical process. There are no 
clavicles. 

In the Uncutata the scapula is always high and rather 
narrow. ‘The prescapular and postscapular fossze are often 
subequal. The acromion and coracoid are never much 
developed. ‘The clavicle is always absent. 

The Pecora (see Fig. 77) have all a very large and very 
slowly and imperfectly ossified suprascapular region (ss) ; 


Sav.) UNGULATA. 233 


when this is removed, as is almost always the case with 
macerated bones, the upper border of the scapula is very 
straight. The acromion usually forms a distinct process, 
but is quite absent in the Giraffe, which has the longest and 
narrowest scapula of the group. 


Fic. 77.—Right scapula of Red Deer (Cervus elaphus), }. ss partially ossified 
suprascapular border ; Af postscapular fossa; af anterior or prescapular fossa ; 
@ acromion; ¢ coracoid; gc glenoid cavity. 


In the Horse the scapula is long and slender, the supra- 
scapular border is rounded, and slowly and imperfectly 
ossified. The spine is very slightly developed ; rather above 
the middle its edge is thickened and somewhat turned back- 
wards ; it gradually subsides at the lower extremity without 
forming any acromial process. The coracoid is a prominent 
rounded nodule. 

In the other Perissodactyles, and in the Pigs and Peccaris, 


234. THE SHOULDER GIRDLE, [CHAP. 


’ 


there is a strongly-marked retroverted triangular process 
on the middle of the edge of the spine, and no true 
acromion ; but in the Hippopotamus there is a small 
acromion and no distinct mid-spinous process. In this 
animal the coracoid is rather long and upturned. 

In the Tapir the coraco-scapular notch is remarkably 
deep. 

The Hyrax manifests its affinity with the Ungulata in the 
form of the scapula, which is generally triangular, with a 
small spine, most prominent and with a retroverted edge 
near the middle, and gradually subsiding at each extremity, 
so that there is no trace of an acromial process. 

The Elephant has a largely developed postscapular fossa 
and a narrow ant.rior fossa. The glenoid border is short, 
and forms a very prominent angle posteriorly with the 
unusually long suprascapular border. ‘The spine is promi- 
nent, and has a very strongly marked process projecting 
backwards from near the middle and a moderate-sized 
acromion. ‘The coracoid is small and rounded. 

The EDENTATA present some very interesting conditions 
of the shoulder girdle. 

In the Cape Anteater (Oxycteropus) the scapula is of 
the most normal form, with well-developed acromion and 
coracoid. The middle of the border of the spine is thick- 
ened and retroverted, and there is a well-marked meta- 
cromion. ‘The clavicle is strong, curved, and dilated at its 
sternal end. 

In the Pangolins (AZanzs) the scapula is broad, and rounded 
above, the anterior margin gently passing into the superior. 
The prescapular fossa is broader than the postscapular. The 
suprascapular region remains cartilaginous. The acromion 
is very small. ‘The coracoid is extremely rudimentary, but 
with a separate ossific nucleus. There are no clavicles. 


Xiv. | EDENTATA. 235 


In the Anteaters (/yrmecophaga) the scapula is also broad 
and rounded, so that there is no distinct angle between the 
anterior and superior margin. The anterior margin is pro. 
duced, to meet the large adze-shaped coracoid, over the 
coraco-scapular notch, converting it into a foramen. ‘The 
spine has a triangular process in the middle, and a long 
slender acromion, without distinct metacromion. ‘The post- 
scapular fossa is nearly equally divided by a second spine. 

It is generally stated that there are no clavicles in this 
genus, but ina Tamandua I found rudimentary, flat clavicles, 


7 Inch in greatest extent, embedded in muscles. 


Fic. 78.—Right scapula of Great Armadillo (Priodoxtes gigas), }. ff postscapula 
fossa; af prescapular fossa; gc glenoid cavity; csz coraco-scapular notch c cora- 
coid ; @ acromion ; / articular surface for humerus. 


The small climbing Cyclothurus didactylus has moderate, 


gently curved clavicles. 
In the Armadillos (Dasypodid@) the scapula is rather 
varied in form. The acromion is always very long and 


236 THE SHOULDER GHEDLE. [CHAP. 


curved ; in many cases it has a distinct articular facet on 
its inner surface for the upper end of the humerus. (See 
Fig. 78, 2.) There is a second spine on the postscapular 
fossa, and always a well-developed clavicle. 

In the Sloths (Lrvadypodide, Fig. 79) the prescapular 
region (af) is larger than the postscapular (f/f). The spine 
arises from little more than the middle third of the bone, 
vertically. In the young of both genera of this family the 
acromion is a long strip of cartilage connecting the spine 
with the end of the coracoid, while the coracoid border of 
the scapula and the coracoid bone join each other in front, 


Fic. 79 —Right scapula and clavicle of Two-toed Sloth (Cholwpus hoffmanni), §. 
af prescapular fossa; Af postscapular fossa; gc glenoid cavity; @ acromion; 
¢ coracoid ; csf coraco-scapular foramen; cd clavicle. 


converting the coraco-scapular notch into a small oval fora- 
men (¢sf). This condition remains in the Two-toed Sloth 
(Cholepus) and the extinct AZegatherium ; but in Bradypus 
the acromion gradually becomes reduced in size, losing its 


XIVe | MARSUPIALIA. 237 


connection with the coracoid, and finally remains a mere 
styliform, or slightly flattened process. 

The coracoid in both forms is unusually large, ossifies 
ectosteally according to Parker, and has an epiphysis on its 
free hook-like extremity. 

The clavicle (cZ) of Cholepus is well developed, attached 
externally to the loop of bone on the scapula, formed by the 
united extremities of the acromion (a) and coracoid (¢), 
and internally by the intervention of a long fibro-carti- 
laginous “omosternum” (degenerating into a mere ligament 
in the adult) to the presternum. In Avradypus the clavicle 
is very small, and separated by a long interval from the 
sternum. It originally articulates at its scapular end, as in 
Cholepus ; but in consequence of the atrophy of the acro- 
mion, it is left attached to the end of the coracoid, in which 
unusual situation it remains through adult life. 

In the MarsuPiA.ia the scapula is tolerably uniform in 
shape. The acromion is long, and the coracoid small, of a 
somewhat hooked form, and thick at the base. It ossifies 
by a separate endosteal nucleus. 

The clavicle is present in all known Marsupials except 
the Bandicoots (Peramelide). It has always a “ mesosca- 
pular segment” at its outer end, and a “ precoracoid seg- 
ment” at its sternal end; these are, however, not ossified. 
Most generally it is attached to the acromion by a rather 
strong ligament, but in the Wombat by a synovial articu- 
lation. It is usually connected to the presternum by omo- 
sternal cartilages of varying length, best developed in the 
Didelphide. 

The shoulder girdle of the MoNotrREMATA (see Fig. 80) 
differs widely, in many points, from that of any other 
Mammal, and far more resembles that of the Lizards. 

The scapula is rather long and narrow, and (especially in 


238 THE SHOULDER GIRDLE, [CHAP. 


the Ornithorhynchus) curved backward and pointed, sickle- 
like, at its upper end. Instead of three it presents but two 
distinct borders and two surfaces; but the more convex 
border (s), which is turned forwards and outwards in its 
natural position, has a small projection (a) near its lower 
end, which affords attachment to the clavicle, and is evidently 
the acromion ; and the whole border may be considered to 
represent the spine. Following the indications afforded by 
the attachment of the muscles, it appears probable that the 
whole inner surface represents the prescapular fossa of the 


Ss 


Fic. 80.—Side view of right shoulder girdle of a young Echidna (Echidna hystrix), 3. 
ss suprascapular epiphysis; ssf subscapular fossa; Af postscapular fossa; cé 
coracoid border; gé glenoid border; s spine; @ acromion; css coraco-scapular 
suture; gc glenoid cavity; ¢ coracoid; ec epicoracoid; cé clavicle; zc interclav.cle; 
ps presternum., 


ordinary Mammalian scapula, and that the anterior portion 
of the outer surface (ff) is the postscapular fossa, and the 
posterior portion of the same surface (ssf) the subscapular 
fossa, these two being divided below by a slight ridge (gé), 
which runs to the edge of the glenoid cavity, and from which 


XIV] MONOTREMATA. 239 


the long head of the triceps muscle takes origin. This 
ridge then answers to the posterior or glenoid border of the 
ordinary Mammal, and the hinder border of the Monotreme’s 
scapula (cb) would correspond to the anterior or coracoid 
border. If this is really the case, the scapula of the Mono- 
treme and that of the Cetacean offer the widest contrast, 
the supposed primitive trihedral rod being flattened in 
opposite directions. In the Cetacean scapula there are two 
nearly parallel surfaces, the postscapular and the subsca- 
pular fossze ; while the third, the prescapular fossa, is reduced 
to the smallest possible width—quite obsolete, in fact—in 
Platanista. In the Monotreme the last-named fossa is so 
expanded that the other two, instead of being parallel to 
each other on opposite sides of the bone, are brought almost 
into one plane, which is parallel and opposite to the sub- 
scapular fossa. 

The coracoid (¢) is a stout subcylindrical bone, expanded 
at its extremities, taking at its upper end a considerable 
share in the formation of the glenoid cavity, and becoming 
firmly ankylosed with the scapula. At its lower end it 
articulates to the side of the presternum, just in front of the 
first rib. 

Placed in front of the inner end of the coracoid is a 
broad, flat, shield-lhke plate of bone (epzcoracoid, ec), the 
rounded inner border of which passes beyond the median 
line, overlapping the corresponding bone of the opposite 
side. In the Echidna the left lies superficially to the 
right, while in the Ornithorhynchus this disposition is 
reversed. 

Upon the front end of the presternum, lying below its 
anterior continuation (f7vosteon, see p. 84) and also below 
the epicoracoids, is a large azygous ‘T-shaped bone (cc, see 
also Fig. 43, p. 85), which has no homologue in any other 


240 THE SHOULDER GIRDLE. [CHAP. XIV. 


Mammal, called zzterclavicle. Its lower end is broad, and 
rests on the expanded straight upper margin of the pre- 
sternum ; it contracts somewhat above, before dividing intoa 
pair of nearly horizontal, slightly curved arms, which extend 
outwards towards, though not quite reaching, the acromion. 
This bone differs from the presternum, and the small proosteal 
plate behind its lower extremity, as well as the coracoids 
and epicoracoids, in being developed in membrane. 

The clavicles (@ ) are simple, elongated, slightly curved, 
thin, splint-like bones, resting upon the anterior surface of 
the arms of the interclavicle, pointed and not quite meeting 
internally, and dilated and articulating directly with the 
acromion at their outer end. 


CHAP TERN: 


THE ARM AND FORE-ARM. 


In the upper segment of the limb proper there is always 
one bone, the Humerus ; in the second segment, two bones 
placed side by side, the Radzus and the Una. 

The Aumerus (except in some of its extreme modifica- 
tions) 1s more or less elongated and cylindrical. It is 
described as having a shaft, and two extremities. The upper 
or proximal extremity has a smooth, convex, generally more 
or less rounded ead (Fig. 81, 2), the axis of which is 
directed upwards and backwards. This, in the living 
animal, is covered with a thin layer of cartilage, and 
articulates by a synovial joint with the glenoid cavity of the 
shoulder girdle. The head is marked off from the shaft 
very indistinctly by a constriction called the meck, imme- 
diately below which, upon the anterior surface of the bone, 
are two rough prominences (¢ and z’) for the attachment of 
muscles, called ¢uberoszties, separated from each other by a 
groove (dg) called the dccipital groove, as the tendon of the 
biceps muscle runs in it after arising from the margin of the 
glenoid fossa. The tuberosities are generally distinguished 


1 The terms of relative position here used are those which the bone 
assumes in the ordinary attitude of a quadruped while standing or 
walking. 


R 


242 THE ARM AND FORE-ARM. [CHAP. 


as great (¢) and smad/ (¢’) from their relative size in Man and 
most Mammals ; the former is also called evterna/, and the 
latter zzterna/, from their relative situation in the most usual 
position of the bone; vadaZ and wnar are also terms 
applied to them in relation to their situation, one on the 
side of the humerus with which the radius, and the other on 
the side with which the ulna, is connected below. 


Fic. 81.—Anterior surface of right humerus of Wombat (Phascolomys vombatus), 3. 
A head; ég bicipital groove; ¢ great or radial tuberosity; 2 small or ulnar 
tuberosity; @7 deltoid ridge; s7 supinator ridge; cf supra-condylar foramen ; 
ec external condyle ; zc internal condyle; av articular surface for radius; az arti- 
cular surface for ulna. 

The lower or distal extremity of the humerus is some- 
what flattened, and usually has a broad, semi-cylindrical 
articular surface, which is received into a corresponding» 
concavity on the upper end of the bones of the fore-arm. 
This is called the ¢rochlea (ar and au). On each side, and 
rather above this surface, 1s a prominence called the condyle, 
one of which is exferna/, or radial (ec), the other zzzernal, or 


ulnar (ic). ‘The latter 1s usually the most prominent. In 


xv.] GENERAL CHARACTERS. 243 


the middle of the lower end, between the condyles, and 
above the thickened articular border, the bone is very thin, 
having a hollow both in front and behind. The latter, 
which is the deepest, is called the auconeal fossa, as it 
receives a projecting part of the anconeal process, or ole- 
cranon, of the ulna, when the fore-arm is fully extended. 
It often happens that these two fossz are so deep that they 
meet, and there is in consequence a vacuity in the bone 
called the supratrochlear or intercondylar foramen. ‘There is 
usually a prominent ridge running upwards for some distance 
on the shaft from the external condyle, called the ectocondylar 
or supinator ridge (sr), which affords a wide surface of origin 
for the supinator muscles of the fore-arm. When much 
developed this ridge terminates above at the groove for the 
passage of the musculo-spinal nerve. When the edge of the 
bone above the inner condyle is much developed, it is some- 
times grooved, but more often obliquely perforated from 
above, downwards and forwards, by a supracondvlar foramen 
(f), through which the median nerve and brachial artery 
may pass.. Lastly, somewhere towards the anterior sur- 
face of the middle of the shaft, on the outer side, there is 
isually a roughened, elevated, longitudinal ridge (d), some- 
times developed into a tuberosity, for the insertion of the 
deltoid muscle, and hence called the deltoid ridge, The 
lower end of this ridge is separated from the upper end of 
the supinator ridge by a wide and shallow groove, wind- 
ing in a spiral manner downwards and forwards round the 
outer side of the shaft of the bone, and indicating the 
course of the musculo-spiral nerve. 

The whole of the shaft of the humerus is .developed 
ectosteally from a single centre of ossification, but at each 
extremity there is a large epiphysis: the upper one in- 
cludes the head and both tuberosities, and is usually formed 

2 


244 THE ARM AND FORE-ARM. [CHAP *” 


by the coalescence of two distinct endosteal nuclei; the 
lower one includes the whole inferior articular surface with 
the condyles, and is formed of three or four originally dis- 
tinct centres of ossification. The lower epiphysis unites to 
the shaft before the upper one. 

The skeleton of the second segment of the upper limb, the 
fore-arm or aztibrachium, consists of two bones called radius 
and wna, placed side by side, articulating with the humerus at 
their proximal, and with the carpus at their distal, extremity. 

In their primitive or unmodified condition, these bones 
may be considered as placed one on each border of the 
limb, the radius being preaxial, and the ulna postaxial. 
The radius articulates above with the preaxial (external) 
side of the humerus, the ulna with the postaxial (internal) 
side of the humerus. 

This position is best illustrated in the fore-limb of the 
Cetacea (see Fig. 99), where the two bones are fixed side by 
side and parallel to each other, the preaxial border being 
external, and the postaxial border internal, in their whole 
extent. | 

In the greater number of Mammals, the bones assume a 
very modified and adaptive position (as will be explained 
more fully in the chapter on the comparison of the fore and 
hind limbs), usually crossing each other in the fore-arm, the 
radius in front of the ulna, so that the preaxial bone 
(radius), though external (in the ordinary position of the 
limb) at the upper end, is internal at the lower end ; and 
the hand being mainly fixed to the radius, also has its pre- 


1 So termed (by Prof. Huxley) in relation to the central axis of the 
limb, when it is extended out from the body in its primitive embryonic 
position, the extensor surface of the arm and back of the hand being 
upwards or dorsal, and the flexor surface of the arm and palm of the 
hand being downwards or ventral. 


xv.] GENERAL CHARACTERS. 245 


axial border internal. In the large majority of Mammals, 
the bones are fixed in this position ; but in some few, as 
in Man, a free movement of crossing and uncrossing, or 
pronation and supination, as it is termed, is allowed between 
them, so that they can be placed in their primitive parallel 
condition, when the hand (which moves with the radius) is 
said to be swzfzne, or they may be crossed, when the hand is 
said to be prone. 

In most Mammals which walk on four limbs, and in which 
the hand is permanently prone, the ulna is much reduced in 
size, and the radius increased, especially at the upper end ; 
and the articular surface of the latter, instead of being con- 
fined to the external side of the trochlea of the humerus, 
extends all across its anterior surface, and the two bones, 
instead of being external and internal, are anterior and 
posterior (see Figs. 82, 83, and 84, p. 248.) 

The ulna is always characterised by a conspicuous, more 
or less compressed prolongation, extending upwards beyond 
the excavated humeral articular surface (sigmoid notch), and 
serving as the point of attachment to the extensor muscles 
of the fore-arm, called the olecranon or anconeal process. 

Each of the bones of the fore-arm has commonly a 
principal centre of ossification for the shaft, and an 
epiphysis at either end. 


Special Characters of the Bones of the Arm and Fore- 
arm in the different Groups. 


Order PrimatTEs.—In Man the humerus is long, slender, 
and straight, with a large globular head. Neither the tube- 
rosities, nor the deltoid and supinator ridges, are much 
developed. The internal condyle is prominent, but there 
is no supracondylar foramen as a normal condition. 


The, anconeal fossa is wide and deep, and sometimes, 


246 THE ARM AND FORE-ARM. [CHAP. 


though not usually, perforated. The lower articular surface 
is divided by a groove into a pulley-like internal portion 
(¢rochlea) for the ulna, and a smalle¥ rounded portion (capv- 
tellum), confined to the front side of the bone, for the radius. 

The whole bone is somewhat twisted on its longitudinal 
axis. Supposing it is so placed that a line drawn _hori- 
zontally through the axis of the head passes directly back- 
wards, another line drawn through the condyles would 
not cross this at a right angle, as in most of the inferior 
Mammals, but its outer end would be directed forwards. 

The radius has the head or proximal end expanded, disk- 
shaped, and cupped at its extremity, which is applied to 
the capitellum of the humerus (see Fig. 82). Below this 
expanded head the bone is comparatively slender, but 
increases in size as it approaches the lower end, which is 
wide from side to side; the surface next the ulna being 
hollowed to receive the lower end of that bone, while the 
Opposite side is produced into the radial styloid process. 
The inferior surface is hollowed for articulation with the 
carpus. The whole bone is slightly curved. Not far below 
the head is a rough prominence, into which the tendon of 
the biceps flexor muscle is inserted. 

The ulna has a large sigmoid excavation above for. 
articulation with the trochlea of the humerus ; the pointed 
elevated anterior edge of this is called the coronoid process. 
Vhe olecranon is scarcely produced upwards beyond the 
hinder edge of the articular surface. Below this, on the radial 
side, is a smaller excavation, in which the edge of the disk- 
like head of the radius plays, being held in its, place in the 
living state by a strong annular ligament, which encircles 
it. The ulna is straighter than the radius, and gradually 
diminishes in size to the lower end, where it terminates in a 
rounded surface, which articulates with the hollow in the 


XV. | PRIMATES. 247 


lower end of the radius ; and also, though not very directly, 
with the upper surface of the carpus. _ By the side of this is 
a small conical process, the wnar styloid process. 

The movement of these bones upon the humerus at the 
elbow-joint is simply that of a hinge, formed mainly by the 
articular surface of the ulna. In pronation and supination, 
which is more free and complete than in any other Mammal, 
the ulna is stationary, and the radius moves ; the upper end 
only on its own axis, being fixed to the side of the ulna by 
the annular ligament, but the lower end rotates round the 
lower end of the ulna, carrying the hand with it. 

The higher Apes have the axis of the humerus almost as 
much twisted on itself as in Man; and they also, almost 
alone among Mammals, resemble Man in not having the 
olecranon process of the ulna prolonged upwards beyond 
the sigmoid notch. Even in the Baboons these special 
anthropoid characters are lost. The humerus has no supra- 
condylar perforation in any of the Old World Szmzzna, nor in 
Ateles, Mycetes or Hapale among the American Monkeys ; 
but in the remaining genera of Cebzde, and in most of the 
Lemurs, such a perforation is found. In the Aye-Aye 
(Chzromys) the supinator ridge is remarkably developed. 
The radius and ulna are distinct in all ; in the higher forms 
(especially the Gorilla) greatly curved, leaving a large space 
between them in the middle of the fore-arm. The power 
of supination and pronation, which in the higher forms 
almost equals that enjoyed by Man, is much reduced in 
the inferior types of the order, although never entirely lost. 

In the Carnivora the head of the humerus has no 
longer that hemispherical form, so well marked in the higher 
Primates. The tuberosities are strong and rough, and 
project upwards beyond the level of the head. ‘The shaft 
is much curved forwards. ‘The deltoid ridge is strong, and 


248 THE ARM AND FORE-ARM. [cHaP. 


extends far down on the bone, especially in the Bears. 
The inner condyle is prominent. The anconeal fossa is 
deep. A supracondylar foramen exists in the Fé/z/@, and in 
most of the Viverride, Mustelide, and Procyonide, but not 
in the Canidae, Hyenide, or Urside. 


Fic. 82. Fic. 83. lig. 84. 


Anterior aspect of the bones forming the right elbow-joint of Man (Fig. 82); of the 
Dog (Fig. 83); of the Red Deer (Fig. 84); all4. humerus; ~ radius; z ulna. 


The radius differs from that of Man, inasmuch as its 
upper end is broad, flattened, and extends further across the 
front of the humeral articular surface, forming part of the 
hinge (see Fig. 83); and, although it is never ankylosed with 
the ulna, scarcely any appreciable amount of movement is 
allowed between them. The ulna has a large compressed 
olecranon, and a shaft gradually tapering to the lower 
extremity. 

In the Pexnipedia the bones of the. anterior limb are very 
short and stout. The humerus has a remarkably prominent 
deltoid ridge, and usually no supracondylar foramen, though 


xv.] INSECTIVORA. 249 


this is present in the Common Seal (Phoca vitulina). The 
upper end of the ulna, and conversely the lower end of the 
radius, are much expanded. 

In most of the INSEcrivora the bones of the arm gene- 
rally resemble those of the Carnivora. In the Hedgehog 
(EZrinaceus) there is no supracondylar foramen in the 
humerus, but a large supratrochlear perforation. In Cen- 
tetes, Rhynchocyon, and nearly all the other genera, there 
is a supracondylar foramen. 

The radius and ulna are generally completely developed 
and distinct; but in Galeopithecus, Macroscelides and Letro- 
dromus, they are fused together inferiorly. 

The Mole (Zadpa) and its allies have a humerus of ex- 
traordinary form, being very short, and extremely broad 
and flattened at both extremities, though contracted in the 
middle. In addition to the narrow oval head for articulation 
with the glenoid cavity of the scapula, there is a larger 
saddle-shaped surface, which articulates by a separate syn- 
ovial joint with the outer end of the coraco-clavicle. ‘The 
deltoid ridge is very prominent, joining the inner tuberosity 
above. From each condyle a slender bony process extends 
upwards. There is a supracondylar foramen. ‘The ulna has 
a greatly developed olecranon, with a narrow keel behind, 
and expanded laterally at the extremity. 

In the Cape Golden Mole (C%rysoch/oris) the humerus 
is much more slender generally than in the true Moles, but 
the inner condyle is extremely elongated. The olecranon 
is long, narrow, and incurved. The fore-arm has a third 
bone, extending from the palmar surface of the carpus 
almost to the elbow, where it has a free termination. ‘This 
appears to be an ossification in one of the flexor tendons. 

The CHiropTera have a long slender humerus, having a 
slight sigmoid curve. The ulnar tuberosity is large. ‘There 


250 THE ARM AND FORE-ARM. ~~ [CHAP. 


is no supracondylar perforation. The ulna is extremely 
reduced, only the upper third being present, and that anky- 
losed with the radius, which forms almost the whole of the 
lower articular surface of the elbow-joint. There is a 
detached sesamoid ossicle on the olecranon. . 

In the Ropent1a the humerus varies much in its charac- 
ters. It is long, slender, and straight, with a very slight 
deltoid ridge, a narrow and laterally compressed inferior 
end, and without prominent condyles in the Hares and 
Agutis. But in the Beaver the deltoid and supinator ridges, 
and the inner condyle, are strongly developed. All inter- 
mediate conditions occur in different genera. As a general 
rule there is a large supratrochlear perforation, but no 
supracondylar foramen. In the Coypu (JZyopfotamus) the 
deltoid ridge is an extremely salient, compressed, and 
everted tuberosity. 

In the fore-arm the two bones are nearly always dis- 
tinct, though closely applied to each other. The breadth 
of the upper end of the radius, and the amount of rota- 
tion permitted upon the ulna, vary much in different 
genera. 

In the great order UnGuLata the humerus is stout and 
rather short. The outer tuberosity is very large, and gene- 
rally sends a strong curved process inwards, overhanging the 
bicipital groove (not, however, in the Horse and Camel). 
The deltoid ridge is usually not strongly marked, and placed 
rather high on the bone ; but in the Rhinoceros it is a very 
salient ridge. The lower end is always particularly straight 
and flat on the inner side (see Fig. 84, p. 248), the condyle 
forming no prominence, and there is never a supracondylar 
foramen. The outer condyle and the ndge above it are 
rather more developed. 

The radius is large at both ends, and superiorly extends 


ie 


ST's.) 


xv] a al CHTA CEA. 251 


across the whole of the humeral trochlear surface (see Fig. 
84). The ulna is a complete and distinct bone in the Pig, 
Hippopotamus, Tapir, and Rhinoceros. In the Ruminants 
it is more or less rudimentary and fixed behind the radius. 
In the Camel the two bones become completely coalesced. 
In the Horse the olecranon and upper part of the shaft 
alone remain, firmly ankylosed to the radius. 

In the PRoBoscipEA the humerus is remarkable for the 
great development of the supinator ridge. The ulna and 


radius are quite distinct, and permanently crossed. The 


upper end of the latter is small, while the ulna not only 
contributes the principal part of the articular surface for the 
humerus, but has its lower end actually larger than that of 
the radius, a condition almost unique among Mammals. 

In Hyrax the humerus is straight, with a very prominent 
outer tuberosity, moderate deltoid ridge, rather compressed 
inferior extremity, large supratrochlear, but no supracon- 
dylar, perforation. The ulna and radius are complete and 
subequal, often ankylosing together in old animals. 

In the Cetracza, the bones of the arm and fore-arm are 
usually very short, broad, and simple in their characters 
(see Fig 99). ‘he humerus has a large globular head, which 
moves freely in the glenoid cavity of the scapula, the tubero- 
sities are fused into one, the bicipital groove being absent ; 
the lower end is broad and flattened, and its inferior surface 
is divided into two nearly equal flat surfaces placed side by 
side (one external, the other internal), and meeting at a very 
obtuse angle. The equally flat upper surfaces of the radius 
and ulna are applied to these and so united that scarcely 
any motion is permitted between them, and often in old 
animals ankylosis takes place at the joint. 

The ulna and radius are parallel to cach other without 
any indication of crossing : the former has a tolerably well- 


252 THE ARM AND FORE-ARM. [CHAP. 


developed olecranon process projecting directly outwards 
from the shaft of the bone ; the radius is extremely simple 
in form, wider below than above. 

In the Rorquals (Balenoptera and Megaptera) these 
bones are considerably elongated. 

In the SrrEntrA the bones of the fore-imb are formed on 
a different type, as there is a distinct, though small and 
simple, trochlear articulation at the elbow-joint. In the 
Dugong, the humerus is small in the middle of the shaft, 
and expanded at each end. ‘The tuberosities are very pro- 
minent, especially the outer one, and the bicipital groove is 
distinct. ‘The internal condyle is prominent, the anconeal 
fossa small, and there is no supracondylar perforation. In 
the humerus of the Manati the bicipital groove is obsolete, 
the two tuberosities coalescing, as in the Cetacea. In other 
respects 1t resembles that of the Dugong. 

The two bones of the fore-arm are, in both genera, about 
equally developed, and generally ankylose together at both 
extremities. 

Order Epenrata.—In the Sloths the humerus is long 
and straight, slender and cylindrical in the greater part, but 
flattened and laterally expanded at the lower end. The 
head is hemispherical, the tuberosities moderately developed, 
and subequal in size, the deltoid ridge very indistinct. In 
the Two-toed Sloths (Cholepus) the humerus is shorter and 
broader than in Bradypus, and has .a large supracondylar 
perforation, which is wanting in the latter genus. 

The radius and ulna somewhat recall those of the 
Primates in their form, and they are capable of a con- 
siderable amount of pronation and supination. ‘The 
olecranon process scarcely PECIEEES beyond the sigmoid 
articular surface. 

The humerus in all the remaining Edentates is stout and 


YV. | MARSUPIALTIA. 253 


broad, and remarkable for the great development of the 
points of muscular attachment, as the tuberosities, deltoid 
and supinator ridges, and internal condyle. ‘These all reach 
their maximum of development in the Armadillos, animals 
which make great use of their fore-limbs in scratching and 
burrowing. ‘The supracondylar foramen is present in all. 
The radius and ulna are also well developed and distinct 
in all, but with no great amount of motion permitted 
between them. ‘The olecranon is always long and strong. 
Order MarsupsaLta.—In the burrowing Wombat (PAasco- 


lomys) the humerus is stout, very broad at the lower end, 


and with strongly developed deltoid and supinator ridges 
(See Fig. 81, p. 242.) These characters prevail generally 
throughout the order, though im a less marked degree. The 
supracondylar foramen is almost always present, some of 
the Dasyures being exceptions. 

The radius and ulna are always distinct and well-developed 
bones. The upper end of the radius is small and rounded, 
and more or less rotation is permitted between the bones, 
even in the carnivorous forms. 

In both the genera of animals constituting the order 
MoNorkEMATA, the humerus is something like that of the 
Mole, short and extremely broad at both extremities, with 
greatly produced inner and outer condyles, though con- 
tracted at the middle of the shaft. 

The radius and ulna are stout, and rather flattened at the 
lower end, where they are of about equal size, and closely 
applied together. The upper end of the olecranon 1s 
widely expanded laterally. 


CHAP Tiss Devil. 
THE MANUS. 


THE terminal segment of the anterior limb is the hand or 
manus.: Its skeleton consists of three divisions: (1) The 
carpus, a group of small, more or less rounded or angular 
bones, with flattened surfaces applied to one another, and, 
though articulating by synovial joints, having scarcely any 
motion between them; (2) the metacarpus, a series of 
.clongated bones placed side by side, with their proximal 
ends articulating by almost immoveable joints with the 
carpus ; (3) the phalanges, or bones of the digits, usually 
three in number to each, articulating with one another by 
freely moveable hinge-joints, the frst being connected in 
like manner to the distal end of the corresponding meta- 
carpal bone. 

To understand thoroughly the arrangement of the bones 
of the carpus in Mammals, it is necessary to study their 


1 “On account of the ambiguity arising from the as yet unsettled con- 
notation of the terms ‘ hand’ and ‘foot,’ I think it better, in a scientific 
treatise, to disuse them altogether, and. . . to adopt for the anterior 
extremity (the carpus and all beyond it) the term manus, and for the 
homotypal posterior segment the term /es. The all but necessity for 
distinct Aomolegical terms for such parts is obvious.” —MIVART, On the 
Appendicular Skeleton of the Primates, Phil. Trans. 1867. 


CHAP. XVI. ] GENERAL CHARACTERS. 255 


condition in some of the lower vertebrates.' Fig. 85 
represents the manus in one of its most complete, and at 
the same time most generalized, forms, as seen in one of 
the Water Tortoises (Chelydra serpentina). 

The carpus consists of two principal rows of bones, an 
upper or proximal row, containing three bones, to which 
Gegenbaur has applied the terms vadzale (r), tntermedium (2), 
and uw/nare (wz), the first being on the radial or preaxial side 


Fic. 85.—Dorsal surface of the right manus of a Water Tortoise (Chelydra ser- 
pentina), after Gegenbaur. vu ulna; R radius; z ulnare; 7 intermedium; ~ radia‘e; 
¢ centrale; 1—5 the five bones of the distal row of the carpus; #z!—v75 the five 
metacarpals. 

of the limb. The lower, or distal, row contains five bones, 

called carpale 1, 2, 3, 4, and 5 respectively, commencing on 

the radial side. Between these two rows, in the middle of 

the carpus, is a single bone, the cevtra/e (c). 

In this very symmetrical carpus, it will be observed that 


the vadiale supports on its distal side two bones, carpale 1 


1 See Gegenbaur, ‘‘ Untersuchungen zur Vergleichenden Anatomie, ” 


1s Heft, Carpus und Tarsus. 1864. 


256 THE MANUS. [CHAP. 


and 2; the zvtermedium is in a line with the centrale and 
carpale 3, which together form a median,axis of the hand, 
while the w/vare has also two bones articulated with its 
distal end, viz. carpale 4. and 5. Each of the carpals of the 
distal row supports a metacarpal. 

In the carpus of the Mammalia, there are usually two 
additional bones developed in the tendons of the flexor 
muscles, one on each side of the carpus, which may be 
called the radial and ulnar sesamoid bones; the latter is 
most constant and generally largest, and is commonly known 
as the fusiform bone. The fourth and fifth carpals of the 
distal rows are always united into a single bone, and the 
centrale is often absent. As a general rule all the other 
bones are present and distinct, though it not unfrequently 
happens that one or more may have coalesced to form 
a single bone, or may be altogether suppressed. 

The table below shows the principal names in use for the 
various carpal bones. Those in the second column, being 
most generally employed by English anatomists, will be 
adopted in the following pages :— 


Radiale = Scaphoid = Waviculare. 

Intermediun = Lunar = Semilunare, Lunaium. 
Ulnare = Cuneiform = 7Zriguetrum, Pyramidale. 
Centrale = Central = Intermedium (Cuvier). 
Carpatle 1 = Trazezium = Afultangulum majus. 
Carpale 2 = Trapezoid = MMiultangulum minus. 
Carpale 3 = Magnum = Capitatum. 

oe = Unciform = Hamatum, Uncinatum. 


The metacarpal bones, with the digits which they sup- 
port, never exceed five in number, and are distinguished by 
numerals, counted from the radial towards the ulnar side. 
The digits are also sometimes named (I) follex, (11) index, 
(IIL) medus, (1V) annularis, and (V) minimus. One or more 


XVI. ] GENERAL CHARACTERS. 237 


may be in a very rudimentary condition, or altogether 
suppressed. If one is absent, it is most commonly the 
first. 

Excepting the Cetacea, no Mammals have more than three 
phalanges to each digit, but they may occasionally have 
fewer by suppression or ankylosis. ; 

The first or radial digit (also called fol/ex) is an exception 
to the usual rule, one of its parts being constantly absent, for 
while each of the other digits has commonly a metacarpal 
and three phalanges, it has only three bones altogether. 
Whether the missing one is the metacarpal or one of the 
phalanges, is a subject which has occasioned much dis- 
cussion, but has not yet been satisfactorily decided. In 
accordance with the most usual custom, the proximal bone 
of this digit will here be treated of as a metacarpal.! 

The terminal phalanges of the digits are often specially 
modified to support the nail, claw or hoof, and are called 
‘“‘ungual phalanges.” 

Very frequently a pair of small sesamoid bones are 
developed in connection with the tendons passing over the 
palmar surface of the articular heads of the metacarpals and 
phalanges, and occasionally (as in the Armadillos) a larger 
bone of similar nature is met with in the middle of the same 
surface of the carpus and metacarpus. More rarely similar 
bones occur on the dorsal surface of the phalangeal articu- 
lations.” . 

Each of the carpal bones ossifies from a single nucleus. 
The metacarpals and phalanges have each a main nucleus 
for the greater part of the bone, and usually an epiphysis at 


1 See Allen Thomson ‘‘ On the Ossification of the First Metacarpal 
Bone.” (Fourn. Anat. and Physiology, Vol. III. p. 131.) 

* These are almost always lost in prepared skeletons, but they occur 
constantly in the common dog. 


258 THE MANUS. [CHAP. 


one end only, this being the distal end of the metacarpals 
(except the first), and the proximal end of the first metacarpal 
and of all the phalanges. In many of the Cetacea epiphyses 
are found at both ends of the bones, and the same takes 
place regularly in the Elephant Seal (MJacrorhinus pro- 
boscidea), and occasionally in some other Mammals. 

In Man the carpus (see Fig 86) is short and broad. Its 
upper border, by which it articulates with the radius, forms a 
regular curve, with the convexity upwards. It has the three 
bones of the proximal row—the scaphoid (s), lunar (7), and 
cuneiform (c)—distinct ; also the usual four bones of the 


Fic. 86.—Bones of the right human carpus, %. s scaphoid ; 2 lunar; ¢ cuneiform ; 
¢m trapezium; ¢d trapezoid; #2 magnum; z unciform; / pisiform; r—v the 
metacarpals. 


distal row, but no central. There is a well-developed rounded 
ulnar sesamoid (the pisiform bone, /) which articulates by a 
smooth facet with the cuneiform, but no radial sesamoid. 
The trapezium (¢m) has a saddle-like articular surface for the 
moveable first metacarpal. The magnum (yz), as its name 
implies, is the largest bone—rather an exceptional condition 
among Mammals; it has a large rounded part or head 
projecting upwards and fitting into a concavity in the distal 
surface of the bones of the proximal row. The unciform. 
() has a strong hook-like process from its palmar surface 
curved towards the radial side. 


XVI. ] GENERAL CHARACTERS. 259 


The first metacarpal is shorter, though somewhat broader 
than any of the others. It is articulated in a different plane 
from them, its palmar surface facing towards the ulnar side 
of the hand, and it is capable of a considerable range of 
movement. The other four metacarpals are nearly equally 
developed, diminishing slightly from the radial to the ulnar 
side; their shafts are slender and rather compressed, 
especially towards the palmar aspect; but they enlarge at 
each extremity, particularly at the rounded distal end or 
head. ‘They are so articulated with the carpus as to allow 
of very little motion. The phalanges are of the normal 
number to each digit, all broad, convex on their dorsal, and 
flattened or slightly hollowed on their palmar, side. The 
proximal is the largest, and the ungual the smallest. The 
latter is flattened and slightly expanded or spatulate at its 
terminal portion. Those of the first digit or thumb are 
stouter than any of the others, those of the fifth digit (little 
finger) are the most slender. ‘The third digit is the longest, 
the second and fourth somewhat shorter and nearly equal, 
the fifth considerably shorter, and the first still more so. 
Sesamoid bones are only developed, behind the metacarpo- 
phalangeal joint of the pollex. 

In the other PriMares, the manus is generally longer and 
narrower than in Man, and as a general rule the first digit or 
thumb is less developed and less freely moveable. In the 
genera Zyoglodytes and Sizmia, as in Man, the proximal 
surface of the carpus articulates with the radius alone, in all 
others it articulates also with the ulna. The scaphoid and 
lunar bones are always distinct. An additional bone (os cev- 
trale, Gegenbaur, Fig. 87, ce) is present in all, except in the 
Gorilla and Chimpanzee, and some of the Lemurs. ‘This 
is considered by some anatomists to be a dismemberment 
of the scaphoid. The pisiform is present in all, and gene- 

S32 


260 THE MANTS. [CHAP. 


rally of a more elongated form, and more salient than in 
Man; and there is usually a small rounded radial sesamoid 
(rs) articulating moveably to the border of the scaphoid 
and trapezium, and connected with the tendon of the flexor 
carpi radialis. 

In the Potto (Perodicticus) there is an additional bone in 
the palmar side of the carpus, an ossification in the igament 
connecting the palmar processes of the trapezium and 
unciform bones, and forming with these processes a com- 
plete bony ring, through which the flexor tendons pass. 


Fic. 87.—Bones of the carpus of a Baboon (Cynocephalus anub:s), }. s scaphoid ; 
é lunar ; ¢ cuneiform; / pisiform ; ce central; 7s radial sesamoid ; ¢z trapezium ; 
td trapezoid ; #z magnum ; wz unciform; I—v the metacarpals. 


The metacarpals and phalanges are of the complete and 
normal number in all, with the following exceptions. In the 
African genus of Long-tailed Monkeys (Co/obus), and also in 
the American Spider Monkeys (Aée/es), the thumb is rudi- 
mentary, having usually but one very minute phalanx, in 
_addition to the metacarpal. In the Potto (Perodicticus) and 
some allied Zemuring, the second (or index) digit is very 
much shorter than the others, and has but two rudimentary 
phalanges. 

The phalanges are generally more curved than in Man, 


1 Mivart, ‘On the Appendicular Skeleton of the Primates ;” Phil. 
Trans. 1867. 


xv. | CARNIVORA. 261 


most notably so in the Orang. The hand of the Mada- 
gascar Aye-Aye (Chiromys) is remarkable for the extreme 
attenuation of the bones of the third digit. 

In the Carnivora, the scaphoid and lunar bones always 
coalesce into a single scapho-lunar bone (Fig. 88, s/), with 
which it is probable the centrale is united, as it never appears! 
as a distinct bone, except sometimes in very young animals. 


Fic. 88.—Bones of the carpus of a Bear (Ursus americanus), 3. sf scapho-lunar 
bone; ¢ cuneiform; Z pisiform ; # unciform ; #z magnum; ¢d trapezoid; Zz tra- 
pezium ; vs radial sesamoid ; i—v the metacarpals. 


The radial accessory ossicle or sesamoid (7s) is generally 
present. All have five digits, with the complete complement of 
phalanges, except the Hyzena, in which genus the pollex is 
represented only by arudimentary metacarpal. This digit is 
usually much reduced in size, and often, as in the Dog, does 
not reach the ground in walking. It is best developed in 
the bears and allied forms. |The first metacarpal is never 
more freely moveable than any of the others. As a general 
rule the middle digit is somewhat the longest, the second and 
fourth nearly equal to it, the fifth shorter, and the first the 
shortest.” 


1 See B. G. Wilder, ‘*On the Composition of the Carpus in Dogs.” 
Bull. Cornell University, Vol. I. p. 301, 1874. 

* The fissiped Carnivora have been divided into two groups, accord- 
ing to the position of the feet in walking—the Plantigrade, or those 
that place the whole of the palmar and plantar surface to the ground ; 


262 THE MANUS. [CHAP. 


As the toes are nearly always armed with large, strong, 
curved, and sharp claws (see Fig. 89), the ungual phalanges 
(p/3) are large, strongly compressed, and pointed, and they 
develop from their base a broad thin lamina of bone (6), 
which is reflected over the root (a2) of the horny claw, and 
holds it more firmly in its place. In those genera, as Fé/7s, 


Fic. 89.—The phalanges of the middle digit of the manus of the Lion (Fe/7s Zeo), 3. 
ph proximal phalanx; 4/2 middle phalanx; £43 ungual phalanx ; a@ the central 
portion forming the internal support to the horny claw ; 4 the bony lamina reflected 
around the base of the claw. 


in which the claws are retractile, the middle phalanx (ff?) 
is deeply hollowed on its ulnar side to receive the ungual 
phalanx when folded back upon it, in the quiescent state of 
the foot. 

In the Prxnipedia, the manus is broader and flatter 
than in the terrestrial Carnivora. The scaphoid and lunar 
coalesce. The ulnar side of the carpus is much reduced, 
the unciform being especially small, and consequently the 
fifth metacarpal articulates partly with the cuneiform of the 


and the Digitigrade, or those that walk only upon the phalanges, the 
metacarpals and metatarsals being vertical and in a line with the fore- 
arm or leg. This distinction, however, is quite an artificial one, and 
every intermediate condition exists between the extreme typical planti- 
grade gait of the bears and the true digitigrade action of the cats and 
dogs. In fact, the greater number of the Carnivora belong to neither 
of these groups, but may be called ‘‘subplantigrade,” often, when at 
rest, applying the whole of the sole to the ground, but keeping the heel 
raised to a greater or less extent when walking. 


XVI. ] INSECTIVORA. 263 


proximal row of the carpus. The pisiform is small. The 
first digit is nearly as long as the second ; the remainder 
gradually diminish in length to the fifth. The ungual pha- 
langes in the ordinary Seals are slender, pointed, slightly 
curved, and not muchcompressed. Inthe Ofarzzde they are 
prolonged beyond the part which bears the very small claw, 
and flattened and truncated at the ends, being continued 
onwards in the living animal as cartilaginous rays, which 
support lobed expansions of the skin. 


Mipf 


‘SS nerd 
NN = = A. 


iit 


F1G 90.—Bones of fore-arm and manus of Mole (Talfa europea), X 2. FR radius; 
U ulna; s scaphoid; ¢Zlunar; c cuneiform ; / pisiform ; 7 unciform ; 7z magnum ; 
td trapezoid; zz trapezium ; ce central ; vs radial sesamoid (falciform); 1—v the 


digits. 

Among the INsEcrivora, the scaphoid and lunar coalesce 
in Galeopithecus, Tupata, Centetes, Solenodon, Erinaceus, and 
Gymnura, but in most of the other forms these bones are 


264 THE MANUS. [CHAP. 


distinct. A distinct os centrale is found in all except in 
Galeopithecus, Potamogale, Chrysochloris, and Sorex. 

There are nearly always five digits, but AAyachocyon and 
Chrysochlorts have but four. ‘The whole hand is generally of 
moderate size, with pointed, conical, slightly curved, ungual 
phalanges. 

In common with every segment of the anterior extremity, 
the manus of the Mole (Za/éa) and its immediate allies is 
extremely modified to suit its fossorial habits (see Fig go). 
It is extremely broad and strong, its breadth being increased 
by the great development of the radial sesamoid (7s), which, 
being sickle-shaped, has received the special name of os 
falciforme. The ungual phalanges are very large, and cleft 
at their extremities. 

In the Cutroprera, the hand is especially modified in a 
totally different manner, constituting the organ of flight. 

In the carpus the scaphoid and lunar are united, and in 
some genera (as P/eropus) the cuneiform is joined with them, 
so that the proximal row contains but a single bone. ‘There 
is no centrale. The pisiform is very small. 

The pollex is short, divaricated from the other digits, not 
enveloped as they are, in a cutaneous expansion, and armed 
with acurved claw. The other digits are extremely long and 
slender. 

In the Frugivorous Bats (Peropus) the second digit has a 
short ungual phalanx and claw, but in each of the other 
digits the middle phalanx is elongated, and gradually tapers 
to the termination, the ungual phalanx being absent. 

In the Insectivorous Bats, the pollex alone has a claw, 
and the elongation of the other digits is chiefly due to the 
metacarpals, the phalanges being small and very slender, 
and usually only two in number, except in the third digit, 
which generally has three. 


XVI. ] RODENTTA. 265 


In the RopeEntT1A, the scaphoid and lunar are very 
generally united (as in Castor, Dasyprocta, FLydrocherus, 
Capromys, Scturus, Arctomys, Mus, &c.), but notin all. An 
os centrale is present in many, as Lepus, Dasytrocta, Hydro- 
cherus, Capromys, and Castor, while in other genera it is 
absent. ‘There is very frequently an accessory ossicle on the 
radial side of the carpus, which is particularly large in the 
Beaver (Fig. gt). There are nearly always five digits, with 


Fic. 91.—Bones of the manus of the Beaver (Castor canadensis), 3. 


the normal number of phalanges, though sometimes (as in 
fLydrocherus) the pollex is rudimentary or suppressed. 

In the Cape Hyrax (Fig. 92, p. 266) there is an additional 
carpal bone (ce), which is probably the os centrale, though 
in form and situation it looks as if it were a dismemberment 
of the proximal part of the trapezoid (¢7). The scaphoid 


266 THE MANUS. [CHAP. 


and lunar are not united, and there are five digits, of which 
the first is extremely small, and has only one minute 
nodular phalanx. In another species, /7. dorsaéts, the pollex 


Fic. 92.—Bones of the manus of Cape Hyrax (/7yvax capensis), nat. size. 


it reduced to a short metacarpal; the fifth digit has but 
two phalanges, and the centrale is united with the trapezoid. 
The ungual phalanges of the three middle digits are small, 
and somewhat conical in form. 

In the Elephant the manus is short and broad, the carpal 
bones are massive and square, and articulate by very flat 
surfaces; they consist of scaphoid, lunar and cuneiform, a 
pisiform and the usual four bones of the distal row, all 
distinct, without the centrale. There are five digits, with 
short stout phalanges, the terminal ones being very small 
and of irregular form. 


XVI.] UNGULATA. 267 


Order UncuLara.—All the known animals of this order 
agree in the complete suppression of the pollex, in the 
absence of an os centrale, and in the complete separation of 
the scaphoid and lunar. The carpus is very compact, the 
bones being generally more or less square, and articulating 


Fic. 93 Fic 94. 


Fic. 93.—Bones of the manus of Tapir (Tafirus indicus), }. ; 

Fic. 94.—Bones of the manus of Rhinoceros (Rhinoceros suneatrensis), 

Fic. 95.—Bones of the manus of a Horse (Zguws cabailus), . 11 and tv rudimentary 
metacarpals. 


by flat surfaces with each other, and with the radius and 
ulnar above. They are eminently digitigrade, the limb 
being entirely supported on the ungual phalanges, which are 
large, and encased in a hoof. 

The digits are arranged according to one or the other of 


268 THE MANUS. [CHAP. 


two distinct types, each characteristic of, and giving name 
to, one of the sub-orders. 

1. The Pertssodactyla, or “‘ odd-toed ” Ungulates, have the 
middle or third digit the longest, and symmetrical in itself, 
the free border of the ungual phalanx being evenly rounded. 
The second and fourth toes may be subequally developed, as 
in the Rhinoceros (Fig. 94), or they may be represented 
only by mere splint-like rudiments of their metacarpals, as in 
_ the Horse (Fig. 95). All intermediate conditions are met 
with in various extinct forms, as Paleotherium, Anchitherium, 
and fipparion. In the Tapir (Fig. 93) there are four 
complete toes, in consequence of the fifth being developed, 
though it scarcely reaches the ground in walking. In other 
respects the foot resembles that of the Rhinoceros, the third 
toe being longest, and symmetrical in itself, and having on 
each side of it the nearly equal second and fourth. In the 
Rhinoceros there is a rudiment only of the fifth metacarpal. 

In the Horse (Fig. 95), the three bones of the first row of 
the carpus are subequal. The second row consists of a 
very broad and flat magnum (vz), supporting the great third 
metacarpal, having to its radial side the trapezoid (/¢), and 
to its ulnar side the unciform (z) which are both small, and 
articulate distally with the rudimentary second and fourth 
metacarpals. ‘The pisiform is large and prominent, flattened 
and curved; it articulates partly to the cuneiform, and 
partly to the lower end of the radius. The single digit 
consists of a moderate-sized proximal, a very short middle, 
and a wide, semilunar, ungual phalanx. There is a pair of 
large nedular sesamoids behind the metacarpo-phalangeal 
articulation, and a single, transversely extended, “ navicular” 
sesamoid behind the joint between the second and third 
phalanx. 

2. The Artiodactyla have the third and fourth digits almost 


XVI.] UNGULATA. 269 
equally developed, and their ungual phalanges flattened on 
their inner or contiguous surfaces, so that each is symmetri- 
cal in itself, but when the two are placed together they form a 
figure symmetrically disposed to a line drawn between them, 
Or, in other words, the axis or median line of the whole 


oe 


= 


y 


=S>= : 
SSS 


UE SIR 


Fic. 97. 
Fic. 96.—Bones of the manus of Pig (Sus scrofa), 3. 


Fic. 97.—Bones of the manus of Red Deer (Cervus elaphus), 1. 
Fic. 98.—Bones of the manus of Camel (Camzelus bactrianus), t. 


manus is a line drawn between the third and fourth digits, 
while in the Perissodactyles it is a line drawn down the 
centre of the third digit. 

In the Swzva, Pigs (Fig. 96), Peccaries, and Hippopotamus, 
the second and fifth toes are well developed, though always 


270 THE MANUS. [CHAP. 


considerably smaller than the third and fourth, all four 
metacarpal bones are distinct, and the manus is compa- 
ratively broad. The second row of carpal bones in the 
Pig consists of a small trapezoid, a moderate-sized magnum, 
anda large unciform. In the Hippopotamus there is also a 
trapezium. 

In the ruminating sections of the sub-order (Figs. 97 and 
98), the third and fourth metacarpals, though originally 
distinct, become more or less conjoined, generally so as to 
form what appears externally to be a single bone, though 
traces of their separate origin always remain ; the two distal 
articular surfaces are quite distinct, each supporting a digit. 
The lateral (second and fifth) metacarpals and digits are 
generally rudimentary, sometimes completely absent. Some- 
times not even the hoofs remain, as in the Giraffe, Prongbuck 
(Antilocapra), and some other Antelopes; sometimes the 
hoofs alone, as in the Sheep and Ox, supported, it may be, 
by irregular nodules of bone, rudiments of the ungual 
phalanges. In the Deer (Fig. 97), the three phalanges are 
complete, sometimes with the lower end of the metacarpal, 
tapering above, and not directly attached to other parts of 
the skeleton of the foot. In other species rudiments of the 
proximal ends only of the metacarpals are present. 

In the Zragudina these metacarpals are completely deve- 
loped, and articulate with the carpus. In /yomoschus, 
belonging to this section, the third and fourth metacarpals 
commonly remain distinct through life, so that the manus of 
this animal scarcely differs from that of one of the Szzna. 

Vhe Zylopoda or Camels, differ considerably from the 


1 The last-named condition occurs in most of the deer of the Old 
World, the former in all the American deer, with Alces, Rangifer, 
Hydropotes, and Capreolus. See Sir Victor Brooke, Proc. Zoological 
Society, 1874, p. 36. 


XVI. ] CETACEA. 275 


true Ruminants in the structure of the fore-foot (see Fig. 
98). In the carpus the trapezoid and magnum are distinct, 
as in the Swzva and Ferissodactyla, whereas these bones are 
confluent in the Pecora and Tragulina. There are no traces 
of any metacarpals or digits, except the third and fourth. 
The metacarpals of these are very long and, asin the Peora, 
confluent throughout the greater part of their length, though 
separated for a considerable distance at the lowerend. The 
distal articular surfaces, instead of being pulley-like, with 
deep ridges and grooves, are simple, rounded, and smooth. 
The proximal phalanges are expanded at their distal ends, 
and the wide and depressed middle phalanges are imbedded 
in a broad cutaneous pad, forming the sole of the foot, on 
which the animal rests in walking, instead of on the hoofs, 
as in other Ruminants. The ungual phalanges are very 
small and nodular, not flattened on their inner or opposed 
surfaces, and not completely encased in hoofs. ‘These 
characters are better marked in the true Camels than in the 
Llamas. 

In the animals constituting the order CETACEA, the manus 
has undergone a special modification, being converted into 
a simple, flattened, oval or falciform, usually pointed flipper 
or paddle, showing externally no signs of division into sepa- 
rate digits, nor any traces of nails or claws. The skeleton, 
however, consists, as in other Mammals, of a carpus, 
metacarpus, and either four, cr more commonly five, digits, 
the great peculiarity of which is, that the number of pha- 
langes is not limited to three, as in all other animals of 
the class, but may extend even to twelve or thirteen. 

In the Whalebone Whales, a large portion of the 
skeleton of the hand remains permanently cartilaginous, and 
the cartilages composing the various carpal bones and pha- 
langes are confluent or slightly separated from each other 


272 THE MANUS. [CHAP. 


by interposed tracts of fibrous tissue, without any synovial 
joints. Nodules of bone are deposited in the centre of 
some of these cartilaginous masses, and slowly reach the 
surface as the animal attains maturity : there are commonly 
not more than five such ossifications. The phalanges 
appear like cylindrical or slightly flattened bony masses, 
with roughly truncated ends, set in a continuous rod of 
cartilage. In this way a certain amount of flexibility and 
elasticity is secured in the flipper, but beyond this there 
is no actual motion between the various bones of which 
it is composed. 

The manus of the Right Whale (Galena mysticetus) 1s 
comparatively short and very broad, having all five digits 
present, and being also extended on the ulnar side by a 
flattened cartilage projecting from the edge of the carpus, 
probably representing the pisiform bone. In an adult speci- 
men there are only three distinct ossifications in the carpus. 
The numbers in the digits are respectively I. 1, II. 4, III. 5, 
_ IV. 4, and V. 3. In the Rorquals (Lalenoptera) the first digit 
is absent, and the manus Is of an extremely elongated and 
narrow form. ‘The carpus has five ossifications, and the 
number of phalanges varies somewhat in different species. 

In the Odontocetes, the ossification of the skeleton of 
the manus is usually more complete than in the Whalebone 
Whales, the carpal bones generally coming in close contact 
at their edges, and assuming a somewhat polygonal form. 
The phalanges are also better ossified, often having epi- 
physes at each extremity, and they are connected together 
by imperfect synovial joints. They are always very much 
flattened, and their extremities being truncated and their 
sides nearly parallel, they are either square or oblong 
in form. In size they gradually decrease to the end of 
the digit, the last often consisting of minute nodules or 


XVI. | CEITACEA: 


granules, so irregularly or im- 
perfectly ossified, and so easily 
lost in cleaning, that it is in 
many cases impossible, when 
describing the skeleton of one 
of these animals, to give the 
exact number of phalanges to 
each digit. 

The determination of the 
homologies of the carpal bones 
of the Cetacea with those of 
other Mammalia is beset with 
difficulties, and has conse- 
quently led to some differences 
of opinion among those anato- 
mists who have attempted it. 
Moreover every species ap- 
pears liable to certain indivi- 
dual variations, and sometimes 
the different sides of the same 
animal are not precisely alike, 
either in the arrangement, or 
even the number of the carpal 
ossifications. 

The pisiform is occasionally 
represented by a small ossifi- 
cation on the ulnar border of 
the carpus. Excluding the 
above, the carpus of the Odon- 
tocetes appears never to con- 
sist of more than six bones, 


i) 
ba | 
ioe) 


eg ae ae 


a 
{r —*), 
WE: 


Fic. 99.—Dorsal surface of bones of 
right anterior limb of Round-headed 
Dolphin (Globtocephalus melas), 5. 
The shaded portions of the digits are 
cartilaginous. 


three belonging to the proximal, and three to the distal 


row. 
ak 


274 THE MANUS. [CHAP. 


The three bones of the proximal row are constant, 
and may easily be identified as corresponding to the scap- 
hoid, lunar and cuneiform of human anatomy, ‘or the 
radiale, intermedium, and ulnare of Gegenbaur. The middle 
one is usually the largest and most thoroughly ossified. 

The three bones of the distal row are generally represented 
by distinct ossifications (corresponding apparently with the 
trapezoid, magnum, and unciform) in the genera //yferoodon, 
Beluga, and Monodon. 

In most cases (see Fig. 99) the bones of the distal row of 
the carpus are reduced to two, which appear to correspond 
best with the trapezoid and unciform, the magnum being 
either absent or amalgamated with the trapezoid." 

The trapezium appears never to be present as a distinct 
bone, although the first metacarpal so often assumes the 
characters and position of a carpal bone, that it may easily be 
taken for it. 

The cuneiform always directly supports the fifth meta- 
carpal, and frequently some part of the fourth. Moreover, 
in those species in which the ulnar side of the carpus is 
greatly reduced, as G/obiocephalus, the fifth metacarpal is 
even connected with the ulna. 

In the Cachalot (Physeter) many of the carpal bones; in 
addition to the usual central nucleus, have epiphysial ossifi- 
cations developed in the periphery of the cartilage, which 
ultimately unite with the central piece of bone. 

All the Cetacea with teeth have five digits, though the 
first is usually rudimentary, and in close contact with the 
metacarpal of the second. In some forms, as Physeter, 
Hyperoodon, Monodon, Beluga, L[nia, Platantsta, and Orca, 
the manus is short, broad, and rounded at its distal 


1 For the reasons for these determinations, see ‘‘ On the Osteology of 
the Sperm Whale ;” Trans. Zoological Society, vol. vi. p. 360. 


EVE] STRENTA. 275 


extremity ; the digits being nearly equally developed, spread- 
ing from each other, and without any excessive number of 
phalanges. In the Grampus (Orca) all the phalanges are 
broader than they are long.! In the Round-headed Dol- 
phins (G/obiocephalus, Fig. ag), on the other hand, the manus 
is extremely elongated, narrow, and pointed. This elongation 
is mainly due to the great development of the second, and, 
though to a less extent, of the third digit; the fourth and 
fifth being quite short, and having but few phalanges. The 
number of phalanges (including the metacarpals) in the 
different dipitsdre respectively I. 4, Il. 14, TLE. 6, 1V2 3, 
GaGL eV: T? 

In the common Dolphin (Dephinus) the manus has the 
same essential form, though in a less exaggerated degree, 
the numbers of the phalanges being I. 2, II. ro, IIJ. 7, 1V. 3, 
and V. 1. The digits are all in close contact. 

Order SrrENIA.—Though in external form, and in being 
enclosed in an undivided integument, the terminal segment 
of the fore limb of the animals constituting this order 
much resembles that of the Cetacea, its skeleton is totally 
different. 

The carpus is short and broad. In the genus JZanatus 
the seven most usual bones of this region are all distinct, 
though there is no pisiform. The trapezoid is very small, 
and placed almost on the dorsal surface of the trapezium. 
The cuneiform is large, and supports the greater part of the 
fifth metacarpal. In Halicore many of the bones of the 
carpus usually coalesce ; thus the first row may consist of 
two bones, a scapho-lunar and a cuneiform, and all the 
bones of the second row may unite together. 

In both genera the digits are five in number, with 

This genus is remarkable for the imperfect ossification of the carpal 
bones. 
i 2 


276 THE MANUS. [CHAP. 


moderately elongated and flattened phalanges, which are 
never increased in number beyond the limit usual in the 
Mammalia. 

Among the animals constituting the 
Order EpENTATA there is great diversity 


AY 2 ) in the structure of the fore-foot. They 
a IND agree, however, in wanting an os centrale, 
uX fle Ph e-ta and (with the exception of AZauzs) in the 
( 1\ presence of distinct scaphoid and lunar 
oda A bones. 
™ Lins In the existing Sloths the whole manus 
e ace is long, very narrow, habitually curved, and 
i) \ terminating in two or three pointed, curved 
pli iF claws, in close apposition with each other, 
i hi incapable, in fact, of being divaricated, so 
Wi that it is reduced to the condition of a 
A yi hook, by which the animal suspends itself 
Py Be to the boughs of the trees among which 
in it lives. , 
aie The carpus is small, and articulates by 


Fic. 1co.—Bones of the g smooth rounded surface with the lower 
right manus of the : 
Two-toed Sloth (Czo- end of the radius. In the Three-toed 
lepus didactyius). }. - é ; 
Sloths (genus 4vadypfus) it consists of 
distinct scaphoid, lunar, and cuneiform bones in the first 
row, but usually of only two bones in the second row, the 
unciform, and a connate magnum and trapezoid, the trape- 
zium being generally ankylosed to the rudimentary first 
metacarpal.! There is a small rounded pisiform, but no 
radial sesamoid. The first and fifth metacarpals are present 
in a rudimentary condition, but bear no phalanges. The 
three middle digits are nearly equally developed. The 
proximal phalanges are extremely short, and become soon 


1 See Journal of Anatomy and Physiology, vol. vii. p. 255. 


XVI] EDENTATA. Pg 


ankylosed to the ends of the metacarpals, so that in adult 
animals one of the usual bones of the digit appears to be 
entirely wanting. ‘The middle phalanges are long and com- 
pressed. The ungual phalanges are also long, much com- 
pressed, gently curved, and pointed. Bony lamine reflected 
from their bases encase and support the roots of the claws. 

In the Two-toed species (genus Cholepus, Fig. 100), the 
magnum and trapezoid are distinct. The functional digits 
are the second and third, and there are rudiments of the first 
and fourth metacarpals, though not of the fifth. The proximal 
phalanges (/') are extremely short, as in Bradypus, but do 
not ankylose with the metacarpals. The ungual phalanges 
are not so long as in Brady pus. 

In the Pangolins (A/anzs) the scaphoid and lunar are united, 
but all the other carpal bones are distinct. There are five 
digits with the complete number of phalanges, which, except 
in the pollex, are short and broad. ‘The distal ends of the 
ungual phalanges have deep median clefts. This phalanx in 
the third digit is immensely developed, and considerably so 
in the fourth. The first, second, and fifth digits are com- 
paratively small. 

In the Cape Anteater (Ovycteropus) the pollex is entirely 
suppressed, but all the other digits are well developed, and 
terminate in subequal, compressed, ungual phalanges of 
moderate size. The second and third digits are nearly 
equal, the fourth and fifth shorter. A sesamoid bone is 
developed on the dorsal side of the metacarpo-phalangeal 
articulations. 

In the true Anteaters (AZvrmecophaga) all the usual carpal 
bones are distinct. The unciform supports the fifth, fourth, 
and a considerable part of the third, metacarpals. ‘The first 
digit is very slender, the second also slender, with com- 
pressed phalanges of nearly equal length. The third digit 


278 THE MANUS. [CHAP. 


is immensely developed ; though its proximal phalanx is 
extremely short, its ungual phalanx is so long that the 
entire length of the digit exceeds that of the second. ‘The 
fourth has a long and rather slender metacarpal, and three 
phalanges gradually diminishing in size, the ungual phalanx 
being very small. The fifth has the metacarpal nearly as 
long, but not so stout as the fourth, and followed by two 
small phalanges, the last rudimentary and conical, and bear- 
ing no nail. 

The little Tree Anteater (Cyclothurus didactylus) has a 
remarkably modified manus. The third digit is greatly 
developed at the expense of all the others ; it has a stout, 
short metacarpal, and but two phalanges, of which the most 
distal is large, compressed, pointed, and much curved, 
bearing a very strong hook-like claw. The second digit 
has the same number of phalanges and bears a claw, but 
is very much more slender than the third. The fourth is 
represented only by a styliform metacarpal, and there are no 
traces of either the first or fifth digits of the typical manus. 
The pisiform is very large. 

In the Armadillos (Dasyfodide), the manus is stout and 
broad, with strongly developed ungual phalanges, adapted 
for digging and scratching. ‘The fifth metacarpal articulates 
with the cuneiform as well as the unciform. ‘There is always 
a very large palmar sesamoid. The digits are almost always 
five in number, but vary much in relative size and structure. 

In the six-banded Armadillos (genus Dasyfus), all the 
digits have the normal number of phalanges (see Fig. ror). » 
The first digit is rather short and especially slender; the 
second is the longest, and has all the phalanges, as well as 
the metacarpal, of nearly equal length ; the third has a long 
metacarpal, then two short broad phalanges, the first being 
especially short, and a long, curved, compressed, ungual 


XVI. | EDENTATA. 279 


phalanx. The fourth and fifth are shorter, but present 
the same general characters, and their metacarpals are also 
reduced in length. 
All the deviations from the normal type of manus ob- 
served in the common Armadillos, when greatly exaggerated 
produce the curiously modified condition seen in the Cabas- 
sou (Xenurus unicinctus). The first and second digits are 


Fic. 1o1.—Bones of the right manus of Fic. 1toz.—Bones of the manus of the 


the Hairy Armadillo (Dasyfus villo- Great Armadillo (Predontes gigas),4. 

Sus), %. @ an accessory carpal ossicle in front 
of the pisiform, which is not seen in 
the figure. 


still more slender and elongated, and retain the normal 
number of phalanges ; but in the other three the metacarpal 
is short and broad, the proximal phalanx is either sup- 
pressed or incorporated with the metacarpal, as in some of 
the Sloths, the middle phalanx is very short, but the ungual 


280 THE MANUS. [CHAP.=) 


phalanx is enormously developed, larger in the third than 
in the fourth and fifth digits. 

A still further modification of the same type is seen in 
the extraordinary manus of the great Armadillo (Prcodon- 
tes gigas), the largest existing member of the group (Fig. 
102). The metacarpals of the three outer toes are still 
further reduced in length, the ungual phalanx of the third 
is increased in size, while that of the fourth, and especially 
the fifth, are greatly diminished. 

In the genus Zo/ypeutes, the manus is formed on a some- 
what similar type; but in the Nine-banded Armadillos 
(genus Zazusta) it is altogether different, the second and 
third toes being subequal (the third the longest), with mode- 
rate, conical, and slightly compressed ungual phalanges : and 
the first and fourth also nearly equal and smaller, all with 
the normal number of phalanges. The fifth is absent, or 
(as in Z: hybrida) represented by three very rudimentary 
nodular bones. 

Order MarsupratiaA.—The carpus never has a distinct 
os centrale. It is commonly stated that there is a scapho- 
lunar bone ; but the lunar, though always small, is distinct 
in Didelphys, Perameles, Dasyurus, Thylacinus, Phalangista, 
and “ypsiprymnus (where it is very minute); and its ab- 
sence in AZacropus appears to be due rather to suppression 
than to coalescence with the scaphoid. In Phascolomys a 
small lunar is present in some individuals, and not in 
others. 

With the exception of the genus Cheropus, all known 
Marsupials possess the normal number of digits and pha- 
langes, and the manus is short and rather broad, with 
moderately developed, compressed, curved, ungual pha- 
langes. 


The little “‘ pig-footed ” insectivorous Marsupial Charopus 


XVI. ] MARSUPIALIA. 281 


castanotis, belonging to the family Peramelide, has a remark- 
ably modified manus (see Fig. 104) in which only two 
digits are functionally developed ; and as the metacarpals 
are very long, and closely pressed together (though not 
ankylosed), and the phalanges are short, and the nails rather 
hoof-like, the whole manus has much general resemblance 


Fic. 103 —Bones of manus of Bandicoot Fic. 104.—Bones of manus of Chwropus 
(Perameles), X 1%. castanotis, X 2. 
to that of the Artiodactyle Ungulates. It presents, how- 
ever, the essential difference that the functional digits are 
the second and third of the normal series, instead of the 
third and fourth. This is proved by comparing it with 
the less modified manus of a true Perameles (Fig. 103). 
The principal changes from the typical mammalian manus 
observed in Ferameles are the great reduction of the 


282 THE MANGS. [CHAP. XVI. 


first and fifth digits ; while the second, third, and fourth 
remain functional, with long ungual phalanges cleft me- 
sially at their extremities. The third is longer than the 
second, and this longer than the fourth. In Chwropus the 
second and third remain, and retain their relative size, 
though comparatively longer, more slender, and with smaller 
ungual phalanges. The fourth digit is rudimentary, but 
with the normal number of phalanges ; the first and fifth 
are entirely suppressed. The carpal bones have their 
normal] relations, but the trapezium is exceedingly reduced. 

Order MonoTREMATA.—In the Echidna the carpus is 
short and broad, and has a very complex articulation 
with the distal ends of the radius and ulna. ‘The first row 
consists of a scapho-lunar and a cuneiform. ‘There is no 
central. ‘The distal row has the usual four bones. The 
pisiform is large, and articulates with the ulna as wel! as the 
cuneiform, and there is a small radial sesamoid, articulating 
with the scapho-lunar. There are also two large sesamoids, 
sometimes united, in the palmar tendons. The digits are 
five in number, all with the normal number of phalanges, 
which are short and broad, except those that bear the 
long, slightly curved, broad nails, with which the animal 
scratches and burrows in the ground. ‘The pollex is more 
slender than the other digits ; it is of about the same length 
as the fifth, the second and fourth are nearly equal and 
longer, and the third slightly the longest. 

In the Ornithorhynchus the manus is comparatively more 
slender and elongated ; but the number and arrangement 
of the bones are the same as in the Echidna. 


CHAPTER XVLIE 


REE (PRLVIC. ‘61D iB. 


THE posterior limb consists of a pelvic girdle and three 
segments belonging to the limb proper, viz. the thigh, the 
leg and the foot, or Zes. 

The Petvic GiRDLE is present in some form in all Mam- 
mals, though in the Cetacea and the Sirenia it is in an 
exceedingly rudimentary condition. 

In all Mammals, except those belonging to the two 
orders just named, each lateral half of the pelvic girdle 
consists primitively, like the corresponding part of the an- 
terior limb, of a rod of cartilage crossing the long axis of 
the trunk, having an upper or dorsal, and a lower or ventral, 
end. The upper end diverges from that of the opposite 
side, but the lower end approaches, and, in most cases, 
meets it, forming a symphysis, without the intervention of 
any bone corresponding to the sternum. 

The pelvic girdle differs from the shoulder girdle in being 
articulated to the vertebral column, at a point near to, but 
not at, the upper end of the rod. 

Like the shoulder girdle, it bears on its outer side, near 
the middle, a cup-shaped articular cavity (acetabulum or 
cotyloid cavity, Fig. 105, a, p. 284), into which the proximal 
extremity of the first bone of the limb proper is recejved. 


284 LHE PEEVIC- GIRDLE, [CHAP. 


Like the shoulder girdle it is divided, by its mode of 
ossification, into an upper (dovsa/) and a lower (ventra/) 
segment, and the point of union between these is near the 
middle of the articular cavity. 

Unlike the shoulder girdle of most Mammals, the lower 
segment is always largely developed, and ossifies from two 


U a“ 
SS “ill i) 


‘Ny 
i? 
/ Hy 


| 


Fic. tos. —Externa! surface of right innominate bone of a young Lamb (Ov/s avves), 
%. /Zilium (gluteal surface) ; sz supra-iliac border ; a4 acetabular border; 2d ischial 
border; 7s ischium ; sf spine; zz tuberosity of ischium; ? pubis; s symphysis ; 
tf thyroid or obturator foramen; @ acetabulum. 


separate centres, which form an anterior and a posterior 
bar, in contact above and below, but leaving a space 
between them in the middle, filled only by membrane, and 
called the thyroid or obturator foramen (thf). 

The upper segment is named the z/wm (/7), the anterior 
bar of the lower segment the pudzs (P), and the posterior 
bar the zsch7um ([s). In the process of growth these three 


XVII. ] GENERAL CHARACTERS. 285 


osseous pieces always coalesce into a single bone, called the 
os tnnominatum. 

Vhis is further completed by the addition of epiphyses ; 
one for the upper extremity of the ilium (corresponding to 
the supra-scapular epiphysis of the shoulder), others for the 
most prominent parts of the lower or free borders of the 
pubis and ischium (symphysis pubis and tuber ischii), and 
also certain epiphysial ossifications developed in the car- 
tilage, at the place of junction of the three main elements. 

There is never any secondary osseous bar in the pelvic 
girdle corresponding to the clavicle of the upper extremity. 

The ilium of Mammals is essentially an elongated, three- 
sided, or prismatic bone, though the relative size and posi- 
tion of the various surfaces and angles may differ greatly 
in different species. In the most characteristic form, one 
of the surfaces is internal, or directed towards the ver- 
tebral column, articulating by a flat irregular surface with the 
lateral “ pleuropophysial” ossifications of the sacral verte- 
bree. This may be called the sacra/ surface (see Figs, 106 and 
HOP. 207, 20d Fig. 108, ss, p. 295.) “Another is directed 
mainly forwards, and may be called anterior or z/zac (zs), as 
it gives origin to the iliacus muscle. The third is posterior 
or gluteal ( gs), as 1t gives origin to the gluteal muscles. 

Of the borders one is external or acetabular (ab), as it 
ends below at the margin of the acetabulum ; another is 
antero-internal or fwdic ( fb), and the third is postero-internal 
or ¢schial (7b), so called because they end below by joining 
the pubis and the ischium respectively. 

The innominate bone is always placed more or less 
obliquely to the vertebral column, the upper or iliac end 
inclining forwards, and the lower or ischio-pubic end turning 
backwards, contrary to the usual direction of the scapular arch. 
In order to give still greater stability and fixity to the pelvic 


286 LUTE PE Te GL, [CHAP. 


girdle, and to incorporate it more completely for mechanical 
purposes with the vertebral column, there is, in addition to 
the articulation between the ilium and true sacral vertebre, 
a very strong double ligamentous union between the ischium 
and the side of the anterior caudal or pseudo-sacral vertebre, 
constituting the greater and lesser sacro-sciatic ligaments, 
which are replaced in some Mammals (as most of the Eden- 
tata) by a complete bony union.! 

‘The two innominate bones, together with the sacrum, 
constitute the pe/zzs, a complete circle of bone, or rather a 
short tube. This has two outlets: an anterior (sometimes 
called zw/et or brim) bounded by the inferior surface of the 
first sacral vertebra above, by the pubic borders of the 
ilia laterally, and by the anterior borders of the converging 
pubic bones, meeting at the symphysis below; and a 
posterior outlet, bounded by the posterior part of the 
sacrum above, by the great sacro-sciatic ligaments laterally, 
and by the converging posterior borders of the ischia below. 
In consequence of the oblique position of the innominate 
bones, the plane of the anterior outlet (in the horizontal 
position of the body) looks downwards and _ forwards ; 
that of the posterior outlet upwards and backwards ; but 
these two planes are not exactly parallel, the long axis of 
the cavity being usually more or less curved. 


Modifications of the Pelvic Girdle tn the different Groups 
of Mammatia. 


Order Prrmates.—The pelvis of Man is very consider- 
ably modified from the usual form met with in Mammals. 


1 Practically, though not morphologically, the pelvis is a part of the 
trunk or axial skeleton. The functions of the hind limb in propelling 
and raising the body necessitate that it should be: so. 


<8 
» a 
P 


‘ 


XVII.] MAN. 287 


The innominate bone (Fig 106) is remarkably broad in 
proportion to its length. The ilium is flattened and ex- 
panded, and has a greatly extended, almost semicircular, 
supra-iliac border (sz). The sacral surface (ss) is small, and 
scarcely rises above the vertebral attachment. The iliac 


Fic. 106.—Ventral surface of right inno- Fic. 107.—Ventral surface of right inno- 
minate bone of Man, 3. minate bone of Dog, 3. 


ss supra-iliac border or crest of the ilium; ss sacral surface; zs iliac surtace; aé 


acetabular border: 44 pubic border; 26 ischial border of ilium; @ acetabulum ; 
thf thyroid foramen; #2 tuberosity of ischium; s symphysis of pubis. 


surface (zs) is very broad and hollowed. ‘The gluteal surface 
is likewise much expanded, and, though presenting several 
curves, is, in the main, convex. ‘The acetabular border (ad) 
is very short, and has a strong, rounded, rough prominence 
for the attachment of the tendon of the vectws (extensor) 


288 LAE PL EELVLC GIRDLE: [CHAP. 


muscle of the leg. The pubic border (0) is slightly 
marked, constituting the Zinea arcuata interna, or linea ilio- 
fectinea of human anatomy. The ischial border (zd) is 
short and deeply hollowed. The acetabulum (a) is large, 
circular, with very prominent borders, incomplete only for a 
small space on the infero-internal aspect. 

The pubis and ischium are short, and widely divergent 
from each other, so that the thyroid foramen (¢#/) is elon- 
gated in the direction across the main axis of the bones. 
The symphysis (s) is rather short, and formed by the 
pubis alone. Each of the apposed surfaces of bone is 
capped by a plate of fibro-cartilage ; these are held to- 
gether by strong ligamentous fibres, while between them 
there is usually a more or less perfect synovial cavity. 
Ankylosis at this spot, so common in the lower Mammalia, 
very rarely takes place in Man. 

The posterior and inferior border of the ischium is thick- 
ened and rounded, and distinguished as the ¢uber zschii (tz). 
Above this, on the hinder border of the same bone, is a 
smooth, hollowed surface, called the lesser sciatic notch, 
surmounted by an angular prominence called the s/zne; 
above the spine the edge of the ischium passes into the 
great concavity of the posterior or ischial border of the 
ilium, and which is called the great sciatic, or, more pro- 
perly, ilio-ischiatic notch. The strong ligaments (sacro- 
sciatic) which pass from the side of the pseudo-sacral and 
caudal vertebree, the one to the tuber and the other to the 
spine of the ischium, convert these notches in the living 
body into foramina. 

The anterior or superior (in the vertical position) outlet of 
the pelvis is subcircular, usually rather broader from side to 
side than from the vertebral to the pubic border. Its plane 
is not far from a right angle with the axis of the vertebral 


XVII. ] PRIMATES. 289 


column. The posterior outlet is also very wide. In con- 
sequence of the great curve of the sacrum, and the short- 
ness of the symphysis, the axis of the whole pelvis 1s 
strongly curved. 

In all the Svmdina the innominate bone, especially the 
iliac portion, is more elongated than in Man ; the anterior 
outlet of the pelvis is longer from above downwards, nar- 
rower, and more oblique ; the tuberosities of the ischia .are 
more everted, and the spine and sciatic notches less marked. 

In the highest forms, such as the Gorilla and Chimpanzee, 
the upper part of the ilium is expanded, flattened, and everted, 
the iliac surface being even wider than in Man, though much 
flatter ; but in the Baboons and Monkeys, the whole ilium is 
long and narrow, the sacral surface rises considerably above 
the sacral articulation, the iliac surface is narrow, the gluteal 
surface is very hollow, and the borders all approximate to 
straight and parallel lines. In the Old World monkeys 
the tuberosities of the ischia are greatly everted, and ter- 
minate in broad, triangular, flattened, rough surfaces, to 
which the ischial cutaneous callosities are attached. 

In the true Lemurs the pelvis is very wide ; the ilia are 
long, narrow, and have a sigmoid curve, while the pubes 
approach each other at the symphysis at a very open angle, 
giving an elegant lyre shape to the anterior outline of the 
pelvis. On the other hand, in the genus Zov7s of the same 
eroup (and to a less extent in Zarséus, Perodicticus, and 
others) the cavity of the pelvis is remarkably narrow from 
side to side; the ilia are straight slender rods, from the 
lower end of which the large, flattened, and compressed 
pubes project forward at a right angle, forming a prominent 
keel at the symphysis. 

In the Carnivora the pelvis is generally elongated and 
narrow, the ilium and ischium being in a straight line, and 

U 


290 TE PRL PLIC GIRL. [CHAP. 


of nearly equal Jength. In most species the ilia are straight, 
flattened, and not everted above (see Fig. 107, p. 287) the iliac 
surface (zs) is very narrow, and confined to the lower part of 
the bone, as the acetabular and pubic borders meet in front 
above ; the gluteal surface looks directly outwards and is 
concave ; the sacral surface (ss) forms a broad flat plane 
above the attachment to the sacrum, the crest being formed 
by the united edges of the sacral and gluteal surfaces, 
instead of the iliac and gluteal surfaces, as in Man. The 
symphysis is long; it includes part of both pubis and is- 
chium, and commonly becomes completely osseous in 
adult animals. The thyroid foramen (¢2/) is oval, with its 
long axis parallel to that of the whole bone. The ischia 
are wide and divergent posteriorly. 

In the Hyzena the pelvis is shorter and wider than in most 
other Carnivora, both the upper ends of the ilia and lower 
ends of the ischia being considerably everted. 

In the Bears the ilia are short and everted above. 

In the Seals the pelvis is small, and of a different form 
from that of the terrestrial Carnivora. The ilia are exceed- 
ingly short, and with much everted upper borders ; the 
pubes and ischia are very long and slender, enclosing a long 
and narrow obturator foramen, and meeting at a symphysis 
of very small extent, in which the bones of the two sides 
are very slightly connected, and capable of being widely 
separated during parturition. 

The pelvis: of the INSECTIVORA varies considerably in 
form. In LRhyuchocyon, Macroscetides, and Tupata, the 
symphysis is long, as in the Carnivora, and becomes 
ankylosed ; in “yrnaceus it is short, though the bones of 
the two sides are in contact ; but in many other genera 
the pubic bones are widely separated in the middle line 
below. 


mL | INSECTIVORA. 291 


The Mole has an exceedingly long, narrow, and straight 
pelvis, the innominate bones lying almost parallel with the 
vertebral column. . Both iltum and upper end of the 
ischium are firmly ankylosed with the sacrum, leaving a 
small sacro-sciatic foramen between them. Though the 
pubic bones do not quite meet in the middle line below, 
the brim of the pelvis is extremely contracted, and the 
pelvic viscera pass below and external to the cavity instead 
of through it. The pubes and ischia are very long and 
straight, and inclose a large, but narrow, oval thyroid 
foramen. 

In the CHTROPTERA, the pelvis is small and narrow; the 
ilia are rod-like, the pubes and ischia are not in a line with 
them, but project forwards. ‘The symphysis is often not 
closed. There is usually a strongly developed ‘ pectineal ” 
process, near the acetabular end of the anterior border of 
the pubis, and which in some genera (e. g. Phyllorhina, 
Tricenops, Asellia), is prolonged so far as to unite with a pro- 
cess from the superior extremity of the ilium, inclosing an 
oval foramen ( preacetabular), as large as, or larger than, the 
thyroid foramen. 

In many of the RopenmTia, as the Beaver, the ilia are 
markedly trihedral, with sides of nearly equal extent ; but 
in the Hares, the outer (acetabular) border is almost obso- 
lete, the gluteal and iliac surfaces are confluent, and both 
face outwards, and the internal surface is largely deve- 
loped above the sacra! attachment. 

The pubes and ischia are always largely developed, flat, 
and diverging posteriorly, the obturator foramen is of con- 
siderable size, and the symphysis is long, and_ usually 
becomes osseous ; in the Guinea Pig (Cavia), however, it 
remains ligamentous, and the bones are widely separated 
during parturition. 

y 2 


292 DHE PELVIC (GIROLE, [ CHAP. 


Order UNcuLata.—In the Fecora the pelvis generally is 
elongated. The ilium is expanded and everted at the 
. upper extremity ; but between the sacral attachment and the 
acetabulum it is much contracted, and its borders rounded, 
so that the divisions of its surfaces are no longer distinct. 
There is usually a deep oval depression above the ace- 
tabulum, just within the attachment of the rectus muscle. 
The anterior outlet forms a regular oval with the long 
diameter between the sacrum and symphysis. ‘The latter 
is very long, including a considerable portion of the ischia. 
The margins of the bones are completed by large epiphyses 
in this region, but ultimately coalesce across the middle line. 
The ischia are much developed ; the tuberosities are large, 
and have on the middle of their outer side a well-marked 
conical process, directed outwards, and very characteristic 
of this group of animals. 

In the Giraffe the pelvis 1s shorter than in most of the 
other Pecora ; the upper ends of the ilia are more expanded, 
the thyroid foramen is nearly circular, and the supra-ace- 
tabular fossa 1s almost obsolete. 

These characters are still more strongly marked in the 
Camels ; while, on the other hand, in the Pigs the pelvis is 
elongated, and much resembles that of the Pecora, but the 
supra-acetabular fossa is wanting. 

In the Perdssodactyla, the ilia are widely expanded above, 
but much contracted on approaching the acetabulum. The 
ischia are less elongated than in the Pecora, and the thy- 
roid foramen is more circular. 

The Elephant has a very peculiar pelvis, the form of the 
ilium, and the arrangement of its surfaces, somewhat recalling 
those of the human pelvis. |The supra-iliac border or crest 
is greatly extended and curves outwards and downwards. 
The sacral surface of the ilium is narrow, and scarcely rises 


XVII. ] STRENTIA. 293 


above the attachment to the sacrum. The iliac and gluteal 
surfaces are widely expanded, especially at the upper part, 
and, the pelvis being set nearly vertically to the vertebral 
column, they face almost directly forwards and backwards. 
_ The outer or acetabular border is short and deeply hollowed. 
The pubic and ischial portions are comparatively small, the 
atter being very little produced backwards beyond the 
symphysis. 

In the Srrenta, the pelvis is extremely rudimentary, being 
composed, in the Dugong, of two slender, elongated bones 
on each side, placed end to end, and commonly ankylosing 
together. The upper one, which represents the ilium, 1s 
connected by a ligament with the end of the transverse pro- 
cess of the sacral vertebra ; the lower one is the ischium, 
or ischium and pubis combined, and approaches, though it 
does not meet, its fellow of the opposite side. 

In the adult Manati, the innominate bone is represented 
by a single irregular triangular bone, connected by rather 
long ligaments with the vertebral column above, and with 
the opposite bone across the middle line. 

There is no trace of an acetabulum, or of any portion of 
the limb proper in any of the existing Sirenia ; but in the 
extinct Halithertum an acetabular depression and rudi- 
mentary femur have been discovered. 

In the Ceracea the pelvis is reduced to a pair. of elon- 
gated, slender bones (each of which ossifies from a single 
centre), placed on each side of, and rather below, the ver- 
tebral column, lying nearly parallel to its long axis (though 
they converge somewhat anteriorly), and opposite the spot 
where the chevron bones commence to be developed 
beneath the bodies of the vertebrae. These bones probably 
represent the ischia, and their principal function is_ to 
give attachment to the crura of the penis or clitoris, as 


294 LAE: PEIVIC GIRDLE, [CHAP. 


the case may be. Hence they are usually more largely 
developed in the male than in the female. 

In the Whalebone Whales they usually have a projecting 
angle placed about the middle, near which, in some species, 
a second small bone, which probably represents the femur, 
is attached by ligament (see Fig. 112, p. 305). Ina full- 
grown male Rorqual (4a/enoptera musculus), sixty-seven feet 
in length, each pelvic bone was sixteen inches long. In the 
Greenland Whale (4alena mysticetus,) they are rather shorter 
‘and stouter. As might be expected, from the rudimentary 
character of these bones, they vary considerably in size and 
form in different individuals of the same species, and often 
on the two sides of the same animal. 

In the Doiphins, they are generally smaller, and more 
simple than in the Whaiebone Whales, and usually quite 
straight, though sometimes arched, or presenting a sigmoid 
curve. 

Order Eprentata.—In the Sloths, the pelvis is very short 
and wide, with tolerably broad flattened ila, and slender 
pubes and ischia, inclosing a large oval thyroid foramen, 
the inferior boundary of which, and the extremely narrow 
ossified symphysis, are formed by the pubis alone. The 
spine of the ischium is produced backwards to unite with 
the transverse processes of some of the pseudosacral ver- 
tebrze, inclosing a sacro-sciatic foramen. ‘The sacro-iliac 
articulation 1s commonly ankylosed. 

In all the other Edentates the pelvis is more or less elon- 
gated, the ilia trihedral, the ischia largely developed, the 
pubes slender, the symphysis exceedingly short, but usually 
ossified, and the thyroid foramen large. In all, except Orye- 
teropus, the ischia unite with the vertebral column. This 
union is carried to its greatest extent in the Armadillos, in 
which animals the broad transverse processes of as many as 


XVII. ] MARSUPIALIA. 


295 


five pseudosacral vertebree may coalesce with each other and 
with the side of the ischium, converting the pelvis into a long 
bony tube, the more so as the ilia are also firmly and exten- 
sively united with the true sacrum. There is usually, especially 


in Orycteropus, a strongly developed 
““ pectineal ” tubercle. 

Order MarsupiaLiA.—In the Ame- 
rican Opossums (Daedée/phys), the ium 
is a very simple, straight, three-sided 
rod, thicker at its upper than at its 
acetabular end, each side being nearly 
equal in extent, hollowed, and sharply 
defined by prominent straight borders. 

In the Kangaroo (MJacropus, Fig. 
108), the three surfaces of the ilhum 
are also well marked and nearly equal ; 
but the whole bone is curved outwards 
at the upper end. 

In the Thylacine and Dasyures the 
ilia are compressed laterally, the ace- 
tabular and pubic borders meeting 
above in front, so that the iliac surface 
is (as in the Carnivora) very narrow, 
and disappears in the upper half of the 
bone, the “‘crest” being formed by the 
united edges of the sacral and gluteal 
surfaces ; whereas in the wide, depressed 
pelvis of the Wombat (Phascolomys), the 
flattening has taken place in the con- 
trary direction, and the iliac surface 


Fic. 108. — Ventral surface 


of innominate bone of 
Kangaroo (dMJacropus 
major), +. St supra- 
iliac border; ss sacral 
surface, 7s iliac sur- 
face ; ab acetabular bor- 
der ; gd pubic border of 
ilium ; fz pectineal tu- 
bercle; «@ acetabulum ; 
thf thyroid foramen ; 7z 
tuberosity of ischium ; 
s symphysis ; 7 “* mar- 
supial”’ bone. 


spreads out to form witb the gluteal surface behind, a wide, 


arching, supra-iliac border and crest. 


The ischia and pubes are always largely developed, and the 


296 THE PEEVIC GIRDLE, [CHAP. XVII. 


symphysis is long and generally ossified. In the Kangaroos 
the pectineal tubercle (7) of the pubis is strongly developed. 

Nearly all Marsupials have a pair of elongated, flattened, 
slightly curved bones (Fig. 108, 7), moveably articulated 
by one extremity to the anterior edge of the pubis, near the 
symphysis, and, passing forwards, diverging from each other, 
within the layers of the abdominal parietes. They are, in 
fact, ossifications in, or intimately connected with, the inner 
tendon or “ pillar” of the external oblique muscle, and there- 
fore come under the category of sesamoid bones. They 
vary in size and shape in different species.. In Dzdelphys 
they are nearly as long as the ilia, while in the Kangaroo 
they are scarcely half the length of that bone. Though 
largely developed in the Dasyures, in the allied genus Zhy- 
/acinus, they are represented only by smail, unossified fibro- 
cartilages. 

These bones are commonly called “ marsupial bones,” 
though they have no special function relating to the ventral 
pouch of the female, being nearly equally developed in both 
sexes, and also in those species in: which the marsupium is 
not present. 


In the Monorremata the pelvis is short and broad - 


~ 


The ila are short, distinctly trihedral and everted above. 
The ischia are large, and prolonged into a considerable 
backward-directed tuberosity. The symphysis is long, and 
formed about equally by pubes and ischium. ‘The thyroid 


foramen is round. ‘The acetabulum is perforated as in Birds. 


The pectineal tubercle is greatly developed. ‘There are large 
‘‘ marsupial” bones in both genera. 


~ 


GHAP TIER Xx Velie. 


WHEE GE VAN EEG: 


THE skeleton of the first segment of the limb proper 
consists of an elongated, more or less cylindrical bone, 
the femur, which is described as having a shaft and two 
extremities. 

The dorsal, or (in the ordinary position of the limb) 
antertor surface of the shaft is smooth and rounded 
from side to side, and generally arched somewhat for- 
wards from above downwards; the ventral or fosterior 
surface is more or less compressed, and has a rough longi- 
tudinal ridge, the “nea aspera. | 
» At the proximal extremity is a hemispherical, smooth, 
articular “head” (Fig. 109, 2, p. 298) which fits into the 
acetabulum of the innominate bone, and is generally more 
round and more distinctly separated from the rest of the 
bone by a constriction or “neck” (7) than is the corre- 
sponding part of the humerus. The axis of the head does 
not coincide with that of the shaft of the bone, but crosses 
it at an angle varying in different animals, being directed 
towards the preaxial! or (in the ordinary position of the 
limb) zzéernal side, and slightly also towards the anterior 
aspect. In nearly all Mammals there is a rounded depres- 


1 See note to p. 244. 


298 LHe PHIGH AND LEG: [CHaP. 


sion near the middle of the surface of the head into which 
the “iganientum teres of the hip-joint is inserted. Both |: 
ligament and depression are, however, . £ 


Qs 


wanting in the Orang Utan, Seals, Sea- = 
Otter, Elephant, Sloths, and the Mono- 
tremata. 

Immediately below the neck of the 
femur are two tuberosities, called ¢ro- 
chanters. One (ét) is a comparatively 
small, conical eminence, situated rather 
to the preaxial side, and called the 
lesser ‘trochanter. ‘The other (gf) 4s 
generally very prominent, projecting 
upwards, as high or higher than the top 
of the head, situated mainly on the 
postaxial border of the bone, but curv- 
ing inwards and backwards at its ex- 
tremity ; this is called the great tro- 

; chanter. ‘To the posterior side of its 
Fic. rog.—Right human ‘ 
femur, dorsal or ante- base there is usually a deep depres- 


riur aspect, }. ‘Lhe 


boundary lines of the Ss10n, the digital fossa. 
ious epiphyses are P 
See ca ences In some Mammals, as the Perisso- 


gt greater trochanter ; 


7+ leecer. ttochamer: a  aactyle Ungulates; somes Rodents*and 
See rea m-  Edentates, there is a compressed ridge 
for muscular attachments, on the post- 
axial side of the shaft, a short distance below the great 
trochanter, distinguished as the ¢hird trochanter. (See Fig. “am 
HLOs? ,p. 30%.) | 
The distal extremity of the femur is thickened, and has a 
large trochlear articular surface for the bones of the leg. 
This surface is narrow in front, and bounded by more or less 
prominent ridges ; posteriorly it is divided by a deep median 
notch (¢zéercondylar) into two prominent rounded eminences, 


— aa 


/ 


xvut.] GENERAL CHARACTERS. 299 


called condyles (Fig. 109, ec and zc). The slightly elevated 
roughed portions of bone above the articular condyles are 
termed the tuberosities. 

The femur has a main centre of ossification for the shaft, 
and epiphysial centres for the head, for each trochanter, and 
for the lower extremity. (See Fig. 109.) In most Mammals 
the great trochanter and head coalesce together before they 
join the shaft. The lower epiphysis is the last to become 
united. 

The skeleton of the second segment of the limb consists 
of two bones, the tdza and fbula,' of which the former 
is the larger in all Mammals. These bones always lhe in 
their primitive, unmodified positicn, parallel to each other, 
the tibia on the preaxial, and the fibula on the postaxial 
side, and are never either permanently crossed or capable 
of any considerable amount of rotation, as in the corre- 
sponding bones of the fore limb. In the ordinary walking 
position the tibia is internal, and the fibula external. 

The tibia has an expanded proximal end, with a flat- 
tened articular surface, divided into two slightly concave 
facets, by a rough median eminence, to which the intra- 
articular or crucza/ ligaments of the knee-joint are attached. 
The shaft is usually more or less trihedral, with one flat . 
surface directed backwards, and one border forwards. The 
upper end of this border is thickened into a rough tuberosity, 
into which the tendon of the great extensor muscles of the 
leg are inserted. The lower end is slightly expanded, and 
has a somewhat square articular surface to receive the proxi- 
mal bone of the tarsus, or astragalus. The inner (or pre- 
axial) side of the bone is prolonged beyond this surface, 
forming a process called évternal malleolus, which is applied 


1 Also occasionally called ferone, whence ‘ peroneal,’ 
structures in relation with it. 


applied to 


300 LHE PAIGE AND DRG. [CHAP. 


to the side of the astragalus, giving additional strength to 
the articulation, called “ankle-joint.” 

The fibula has a slender and generally compressed shaft, 
and is somewhat expanded at each extremity. Its upper 
end usually takes no part in the knee-joint, being con- 
nected, by a separate synovial joint, with the tibia just 
below that articulation. The lower end, however, forms 
the outer side of the ankle-joint, under the name of 
external malleolus. 

In many Mammals the fibula is in a more or less rudi- 
mentary condition, and it often ankyloses with the tibia at 
one or both extremities. 

As a general rule each of these bones has a principal 
centre of ossification for the shaft, and an epiphysis at either 
extremity. 

In the neighbourhood of the knee-joint, certain sesamoid 
bones are often found in connection with the tendons which 
pass over the various bony prominences. 

The largest and most constant is the fate/a, placed on 
the anterior surface of the joint, in the conjoined tendon 
of the four great extensor muscles of the leg, and having 
a smooth articular facet, which plays upon the narrow 
anterior part of the inferior articular surface of the femur, 
and forms part of the wall of the cavity of the knee-joint. 
This bone varies considerably in form, being in some cases 
broad, flattened, or lozenge-shaped, and in others, laterally 
compressed or oval. It is found in an ossified condition 
in all Mammals, with the exception of a few of the Mar- 
supialia. 

There are also very frequently smaller ossicles, one 
or two in number, situated behind the femoral condyles, 
called fabelle ; and occasionally there is a wedge-shaped 
bone within the joint, lying on the articular surface of the 


RVI; | PRIMATES. 301 


tibia, an ossification of the internal interarticular semilunar 
cartilage. 


Special Characters of the Bones of the Thigh and Leg in the 
various Groups. 

In Man, the femur (see Fig. 109, p. 298) is long and 
rather slender, the shaft is curved forwards, the head is 
large and globular, the neck elongated and narrow. 

In the Gonilla, the femur is much shorter and broader ; 
the head is smaller and less globular, the neck is shorter 
and set on the shaft more at a right angle. In the Chim- 
panzee the femur more resembles that of Man. In the 
Lemurs it is very slender and straight, the head is globular, 
and the neck very short. 

The tibia and fibula are distinct, and well developed in 
all the Primates, and are united with each other only at 
their extremities. Fabellz: are wanting in the highest forms, 
but generally present in the others. The patella is usually 
broad and flat, and more or less lozenge-shaped. 

In the terrestrial CaRNIvorA, the femur is straight, mode- 
rately slender, and with rather a smali head. ‘The fibula 1s 
slender, and in the Dogs curved towards the tibia, the lower 
half being closely applied to that bone ; but in the Bears, 
and many others, there is a considerable interval between 
the bones throughout, except at their articular extremities. 
Fabelle are generally present. 

In the Seals, the femur is exceedingly short, broad, and 
flattened, with a globular head and an extremely short neck. 
The fibula is almost as large as the tibia, especially at -the 
distal end. These bones are commonly ankylosed together 
at their proximal extremities. 

Among the Insectivora, the Hedgehog has a. strong 
ridge below the great trochanter of the femur, and several 


3202 LEO LEIGH AND) L5G. [CHAP. 


other forms have a similar rudiment of a third trochanter. 
As a general rule the fibula is slender, and in its lower half 
ankylosed with the tibia, but it is complete and distinct in 
the genera Galeopithecus, Tupaia, Centetes, Hriculus, and 
Solenodon. 

In the Curroprera, the femur is slender and straight, 
with trochanters of nearly equal size, and with a small 
globular head, set on a very short neck, with its axis 
pointing almost directly to the anterior or dorsal surfaces of 
the bone. The fibula varies in condition. In Freropus it is 
extremely slender, and the upper end is atrophied, but in 
many of the insectivorous Bats it is well developed. 

In the RopENTIA the femur varies much. In the Hares 
and Squirrels it is long and slender, with a third trochanter 
immediately below the great trochanter. In the Beaver it is 
broad and flat, and has a strong ridge about the middle of 
the outer side of the shaft. In many other forms neither of 
these accessory prominences exist, but the great trochanter 
is usually much developed. 

In some forms, as the Beaver, the fibula is distinct, 
strongly developed, and separated from the tibia, except at 
the extremities, by a wide interosseous space. In others, as 
the Hares, it is slender, and in its distal half united with the 
tibia. The patella is generally elongated, fabellz are usually 
developed, and there are often wedge-shaped ossifications 1n 
the semilunar cartilages of the knee-joint. 

In the UnGutLata, the femur is rather compressed, espe- 
cially at the lower end. ‘There is no distinct constriction 
of the neck, separating the head from the rest of the bone. 
The great trochanter is very large, and usually rises above 
the level of the head. The small trochanter is not very 
salient, and sometimes, as in the Rhinoceros (Fig. 110), is a 
mere rough ridge. The inner edge of the anterior part of the 


XVIII, } UNGULATA. 303 


inferior articular surface is very prominent. In all the 
Perissodactyles there is a strongly marked third trochanter 
(¢’), in the form of a compressed ridge curving forwards. 
This is entirely absent in all the known Artiodactyles. 


Fic. 110.—Anterior aspect of right femur of Rhinoceros (Ainoceros indicus), 3. 


A bead ; ¢ great trochanter; ¢ third trochanter. 


The fibula is subject to great variations among the 
different members of the order. In the Rhinoceros, Tapir, 
Pig, and Hippopotamus it is complete and distinct, though 
slender in proportion to the tibia. In the Horse a mere 
styliform rudiment of the upper end is present. | 

In all Pecora and Zlopfoda, a small distinct bone, having 
a very definite form, articulating with the lower end of the 
tibia, and forming the external malleolus, appears to 
represent the distal extremity of the fibula (see Fig. rrr). 
There is occasionally in addition a slender styliform rudi- 


304 THE. TG AND LG: [CHAP. 


ment of the proximal extremity, but the two are never united 
together by bone. 


Fic. r11.—Anterior aspect of lower end of the right tibia and fibula of Red Deer 
(Cervus elaphus), 3. ¢ tibia; _/ fibula. 


In the Zragudina, the fibula is long and slender, and com- 
plete, but its lower end is indistinguishably blended with 
the tibia. 

The patella is well ossified, and usually somewhat trian- 
gular, with the broad end upwards; but fabelle are not 
commonly developed in the Ungulata. 

In the Hyrax there is a slight ridge on the femur in the 
place of a third trechanter. The fibula is complete, thickest 
at its upper end, where it generally ankyloses with the tibia. 

The femur of the Elephant is long and very straight ; the 
axis of the head is more in a line with that of the shaft than 
usual. The great trochanter is not much developed, and 
the small trochanter is nearly obsolete. The fibula is com- 
plete, distinct, and siender, though considerably enlarged at 
the lower end. . 

In the CETACEA, certain small nodular bones or cartilages 
attached by fibrous tissue to the outer side of the pelvic 
bone in some of the Whalebone Whales, are commonly 
regarded as rudimentary and functionless representatives 


Sy. | GETACEA. 305 


of the skeleton of the hind limb. In the Greenland Whale 
(Fig. 112), there is a proximal, somewhat pear-shaped bone 
(/), about eight inches in length, and a smaller conical distal 
bone (¢), which may represent the femur and tibia respec- 
tively, as suggested by their discoverer, Professor Reinhardt. 


Fic 112.—Side view ot bones of posterior extremity of Greenland Right Whale 
(Balena mysticetus), 4, from Eschricht and Reinhardt. Zz ischium; / femur; 
# accessory ossicle, probably representing the tibia. 


In Megaptera longimana there is but one such bone, and in 
an adult Fin Whale (Lalenoptera musculus), sixty-seven feet 
leng, this was found to be only represented by an oval 
nodule of cartilage about the size of a walnut. Even this 
is wanting in some species of the group, as B. rostrata. 

No trace of any structure representing the skeleton of 
the hind limb, beyond the pelvis, has yet been detected in 
any of the Odontocetes. : 

In none of the existing SIRENIA are there any rudiments 
of the hind limb proper, but the extinct Haltherium had an 
ossified femur, articulated to a well-defined acetabulum in 
the pelvis. 

In the terrestrial and tossorial EpENTATA the femur is 
generally short and broad. ‘There is a third trochanter in 


1 See ‘‘ Recent Memoirs on the Cetacea ;” Ray Society, 1866, p. 134. 
x 


306 THE THIGH AND LEG: [CHAP. 


the Armadillos and Ovycteropus, and a sharp ridge along 
the whole external border in AZyrmecofphaga. ‘The fibula is 
as long as the tibia. In the Armadillos these bones are 
commonly ankylosed together at each extremity, but curve 
away from each other at the middle, leaving a wide inter- 
osseous space. In the Anteaters they are both nearly 
straight and parallel. 

In the Sloths the femur is long, slender, and flattened 
from before backwards. ‘There is no third trochanter ; the 
head is large and globular, and placed near the middle of 
the proximal end of the shaft, with the axis of which it 
more nearly coincides than in most Mammals. ‘The tibia 
and fibula are complete, and more nearly equal in size than 
in most Mammals. ‘They are both curved, so as to be 
separated considerably in the middle part of the leg. The 
lower end of the fibula has a conical prominence which 
turns inwards, and fits into a depression on the outer side 
of the articular surface of the astragalus, as a pivot into 
a socket. 

In none of the MarsupIALia is a third trochanter pre- 
sent on the femur. ‘The fibula is always well developed, 
and its upper extremity is often produced into a well-marked 
process, to the top of which a sesamoid bone is not un- 
frequently attached; but, on the other hand, the patella, 
except in the Peramelide, is unossified or quite rudimentary. 
In the climbing Australian Phalangers and Koalas, which 
have broad hind feet, with an opposable hallux, there is a 
greater freedom of movement between the fibula and tibia 
than in other Mammals, approaching in some degree to the 
rotation often permitted between the radius and ulna. 

In the Monotremata the femur (Fig. 113, 7/) is of very 
remarkable form, being short, flattened from before back- 
wards, narrow in the middle of the shaft, and very broad 


XVIII. J MONOTREMATA. 307 


at each end ; the trochanters are both well developed, and 
the head placed between them on a very short neck, and with 
its axis directed quite towards the anterior or dorsal aspect 
of the bone. The fibula (/’) is large and straight ; it has 
a broad flattened process, completed, by an epiphysis, pro- 


Fic. 113.—Anterior aspect of bones ot right leg ot Oruithorhynchus paradoxus, }. 
/femur ; ¢ tibia; /” fibula; Z patella. 


jecting from the upper extremity above the point of articu- 
lation with the tibia, much resembling the olecranon of the 
fore limb. The tibia (¢) is strongly curved in Ovnithorhynchus, 
but straight in Echidna. In both genera the patella () is 
well developed. 


CHAPTER XIX; 


THE HIND: FOOT OR PES. 


THE terminal segment of the hind limb is the foot or es. 
Its skeleton presents in many particulars a close resemblance 
to that of the manus, being divisible into three parts :—(1) a 
group of short, more or less rounded or square-shaped 
bones, constituting the ¢arsws , (2) a series of long bones 
placed side by side, forming the mefatarsus ; and (3) the 
phalanges of the digits or toes (see Fig. 114, p. 310). 

The metatarsal bones never exceed five in number, and 
the phalanges follow the same numerical rule as in the 
manus, never exceeding three in each digit. Moreover, the 
first digit (counting from the tibial side), or Za//ux, resem- 
bles the pollex of the hand in always having one segment 
less than the other digits. 

The bones of the tarsus in many of the lower Vertebrata 
closely resemble both in number and arrangement those of 
the carpus, as shown in Fig. 85, p..255. They have been 
described in their most generalized condition by Gegenbaur 
under the names expressed in the first column of the 
following table." The names in the second column are 
those by which they are most generally known in this 


1 “*Untersuchungen zur Vergleichenden Anatomie.” Carpus und 
Tarsus. 1864, 


CHAP, XIX.’ GENERAL CHARACTERS. 309 


country, and which will be used in the present work, while 
in the third column some synonyms, occasionally employed, 
are added. 


Tibiale 


L[ntermedium \ oe ao eae 
fibulare = Calcaneum = Os caleis. 
Centrale = Navicular = Scaphordeum. 
Tarsale 1 = Internal Cuneiform = LZxtocuneiforme. 
Tarsale 2 = Middle Cuneiform = Afesocunetforme. 
Tarsale 3 = External Cuneiform = L£ctocuneiforme. 
pee Rae ae grr 


Tarsales5  § 


The bones of the tarsus of Mammals present fewer diver- 
sities of number and arrangement than those of the carpus. 
The proximal row (see Fig. 114) always consists of two 
bones, the astragalus (a, which according to Gegenbaur’s 
view represents the coalesced scaphoid and lunar of the 
hand) and the calcaneum (c). The former is placed more 
to the dorsal side of the foot than the latter, and almost 
exclusively furnishes the tarsal part of the tibio-tarsal or 
ankle-joint. It has a rounded anterior or distal projection 
called the “head.” The calcaneum, placed more to the 
ventral or “plantar” side of the foot, is elongated back- 
wards to form a more or less prominent tuberosity, the tuber 
calcis, to which the tendon of the great extensor muscles of 
the foot is attached. The wavzcular bone (7) is interposed 
between the proximal and distal row on the inner, or tibial, 
side of the foot, but on the outer side the bones of the two 
rows come into contact. The distal row, when complete, 
consists of four bones, which, beginning on the inner side, 
are the three cuneiform bones, internal (c'), middle (c), and 
external (c*), articulated to the distal surface of the navicular, 
and the cuboid (cb) articulated with the calcaneum. Of these 
the middle cuneiform is usually the smallest in animals in 


310 THE FIND FOOT OR PES: [CHAP. 


which all five digits are developed ; but when the hallux is 
wanting, the internal cuneiform may be rudimentary or 
altogether absent. 


Fic. 114 —Bones of a right human foot, showing the epiphyses, 4. 7 tarsus; 7 
metatarsus ; PA phalanges; c calceaneum; a@ astragalus; c6é cuboid; 7 navicular ; 
ct internal cuneiform ; c* middle cuneiform ; c3 external cuneiform ; the digits are 
indicated by Roman numerals, counting from the tibial to the fibular side. 


The three cuneiform bones support the first, second, and 
third metatarsals respectively, the cuboid supports the fourth 
and fifth ; they thus exactly correspond with the four bones 
of the distal row of the carpus. 

In addition to these constant tarsal bones, there may 
be supplemental or sesamoid bones ; one situated near the 
middle of the tibial side of the tarsus, largely developed in 
many Carnivora and Rodents ; another, less frequent, on the 
fibular side; and a third often developed in the tendons 


mx. | GENIRAL CHARACTERS. 311 


of the plantar surface of the tarsus. There is also usually 
a pair of sesamoid bones opposite each metatarso-phalangeal 
articulation, on its plantar aspect. 

The development of the bones of the foot corresponds in 
the main with that of the bones of the manus. Each tarsal 
bone is ossified from a single centre, but the calcaneum has 
in addition an epiphysis for the most projecting part or 
tuberosity. The four outer metatarsals have each one 
centre from which the shaft and- proximal end is ossified, 
and a large epiphysis at the distal end; the first meta- 
tarsal (if it should be so called) and all the phalanges have 
an epiphysis only at the proximal extremity. This rule is 
almost universal, the most notable exception being found 
in the Seals, in which animals (see Fig.-116, p. 315) each 
of the metatarsals and all the bones of the toes, except 
the terminal phalanges, have epiphyses at both ends of 
the shaft. 


Order Primates.—In Man (see Fig. 114) the foot is 
broad, and in the ordinary standing position the whole 
length of the plantar surface (at least its outer edge) rests 
on the ground, the main axis of the foot being at a right 
angle with that of the leg. The inner or tibial side of the 
foot is arched before backwards, each extremity only rest- 
ing on the ground. 

The tarsus is longer than the metstarsus, and the latter is 
longer than the digits, but the forms and relations of the tarsal 
bones are quite characteristic of the general Mammalian 
type, and the five digits are present with the complete 
number of phalanges. ‘The hallux is much stouter than any 
of the others, though usually not quite so long as the second 
toe. Its metatarsal is articulated to a nearly flat surface on 
the internal cuneiform, directed distally, so that it is placed 


312 THE HIND FOOT OR PES. [CHAP. 


in the same plane as the other toes, and cannot be freely 
separated from, or opposed to, them. ‘There are no supple- 
mentary tarsal bones, and sesamoids are developed under 
the metatarso-phalangeal joint of the hallux only. The 
phalanges are much smaller, shorter, and more compressed 
than are those of the manus. The ungual phalanges are 
very small, depressed, and somewhat spatulate. 

The principal distinction of the foot of the Szmzzxa from 
that of Man is that it is more or less modified into a grasping 
organ. The tarsal and metatarsal bones and phalanges are 
the same in number and relative position, but the articular 
surface of the internal cuneiform for the hallux is saddle- 
shaped, and is directed obliquely towards the inner or 
tibial side of the foot. The consequence is that the hallux 
is not only somewhat separated from the other digits, but 
is also set in a different plane, so that when it is flexed it 
turns towards the sole of the foot, and becomes opposed to 
the others, much as the thumb does in the human hand. 
It is this peculiarity of the pes which has given rise to the 
term guadrumanous, or “ four-handed,” often applied to this 
group of animals. 

The hallux is usually relatively shorter than it is in Man. 
In the Orang (Szmza satyrus) it is particularly short, and 
often wants the terminal phalanx, while the metatarsals and 
the phalanges of the other digits are long and curved, the 
proportions of the three segments of the foot being exactly 
the reverse of those of Man, as the tarsal segment is 
shortest, and the phalangeal the longest. 

The form of the articular surface of the astragalus, and 
especially the free mobility of the navicular and cuboid 
bones on the astragalus and calcaneum, cause the foot of 
the Orang to be set very obliquely on the leg, so that when 
placed on a level surface the fibular border only rests on the 


— 


wrx. PRIMATES. 313 


ground, and the sole is directed inwards. This position suits 
well for grasping vertically-placed boughs of trees, but is ill 
adapted for standing or walking on the ground. A similar 
disposition is seen in a varying degree in most of the 
Monkeys, but in none so markedly as the Orang, in which 
animal all the peculiarities by which the simian is dis- 


j ah 


Fic. 115.—Right pes of Tarsius spectrum (nat. size). a@ astragalus ; ¢ calcaneum ; 
z navicular; cl internal cuneiform ; c2 middle cuneiform ; c3 external cuneiform ; 
cb cuboid ; 1 to v the digits. 


tinguished from the human foot, are most strikingly 
displayed. 

There are usually two sesamoid bones behind each 
metatarso-pnalangeal joint, and a single one behind the 
cuboid in the tendon of the peroneus longus muscle. 

The structure of the foot of the Zemurina resembles 
generally that of the Szmztna, and_is in fact one of the 


314 IGE HIND FOOT OR LES. [CHAP. 


principal bonds of union between these groups. The hallux 
is large and opposable, with a flattened ungual phalanx. 
The second digit in Zemur has a narrow, pointed, ungual 
phalanx, while that of the other digits is flat and spatulate, as 
in the Szmizna. In Chiromys all the ungual phalanges, except 
that of the hallux, are compressed, curved, and pointed. 

In Perodicticus there is a supplemental ossicle in the 
transverse ligament of the plantar surface of the tarsus, 
corresponding to that met with in the carpus (see p. 260). 

A remarkable elongation of the tarsal segment of the pes 
occurs in the Galagos ( O¢olicnus), owing to the modification 
of two bones, the calcaneum and the navicular; the distal 
portion of the former, and the whole of the latter, having the 
form of nearly cylindrical rods placed side by side, while 
the other. bones retain nearly their normal form and propor- 
tions. <A precisely similar modification is carried to a still 
greater extent in the genus Zarszus (see Fig. 115, p. 313). 

All the terrestrial CARNIvoRA have the normal number of 
tarsal bones, with very little deviation from their normal 
form and relations. 

The hallux is present and well developed, though shorter 
than the other toes in the Urscde, Procyonide, Mustelide, 
and most of the Veverrid@e. In the Canidae, Hyenide, and 
Felide, it is only represented by a rudimentary metatarsal. 
The other four metatarsals and digits are always well de- 
veloped and subequal. The ungual phalanges in the Fede 
present the same characters as those of the fore limb (see 
D: 202). 

In the Bears, the foot is flat, broad, and plantigrade. In 
the Dogs and Cats, it is longer and narrower, and the heel 
is raised from the ground in walking. 

In the Sea Otter (Zuhydra), the hind foot approximates 
to that of the Seals. It is very large and flattened, almost 


ie | CARNIVORA. 205 


fin-like, and much everted ; but the hallux is still shorter 
than any of the other digits, and the two outer toes are the 
longest. 

In the Seals the pes is completely modified for a special 
purpose. It has no longer any function as an organ of 
support or progression on land, and is habitually directed 
backwards, with the dorsal surface outwards, and the 


Fic. 116.—Dorsal surface of right pes of young Elephant Seal (M/acrorhinus pro- 
boscidea), 1, showing the epiphyses. The letters as before. 


5) 


plantar surface in contact with the corresponding part of 
the opposite limb. The calcaneum is very short, its tube- 
rosity being almost obsolete. The two lateral digits (first 
and fifth) are both longer and much stouter than the others ; 
the middle digit is the shortest. In the Elephant Seal 
(Macrorhinus proboscidea), all the phalanges (except the 


316 THE HIND FOOT. OR PES. [CHAP. 


terminal ones) have epiphyses at both ends of the shaft 
(see Hic. 146, p.315). 

In the Ofarizde, or Eared Seals, and the Walrus, which 
use the hind feet in walking, these modifications from the 
ordinary type are not so marked, the calcaneum having a 
greater backward projection, and all the digits being of 
nearly equal length. In both there is a large sesamoid on 
the tibial side of the tarsus. 

In the greater number of the animals of the order In- 
SECTIVORA the tarsus is quite normal, and there are five 
digits, all with curved, pointed, moderately developed 
ungual phalanges, the hallux being the shortest. In the 
Mole, the pes is narrow, having none of the modifications 
of structure observed in the manus, except that there is 
an unusually large slender sesamoid on the tibial side of 
the tarsus, corresponding to the falciform bone of the fore 
limb. In the Water Moles (JZyoga/e), the pes is remark- 
ably large and almost fin-like. 

In the African genera Petrodromus and Rhynchocyon, the 
hallux is only represented by a rudimentary metatarsal. 
The last-named animal has a remarkably elongated pes, 
produced partly by the length of the metatarsals, and partly 
by a peculiar elongation of all the bones of the distal row 
of the tarsus, the cuboid, and three cuneiform bones. Con- 
trary to what occurs in the Galagos, the navicular and cal- 
caneum are of normal proportions. 

Order CHIROPTERA.—The tarsus is very short; the tuber 
calcanei a slender curved process; the metatarsals are 
equal and rather short ; the phalanges elongated and sub- 
equal in length, the hallux being rather the shortest ; the un- 
gual phalanges are long, curved, compressed, and pointed. 

Order RopeNTIA.—The structure of the pes varies much in 
different members of this order. In the Beaver, as in most 


yd 


the singular condition of pes met with in 


RIK | RODENTTA. au7 


swimming quadrupeds, it is disproportionately large and 
flat. The five digits are well developed, but the third and 
fourth are considerably longer and stouter than the others. 
The head of the fifth metatarsal is articulated to the outer 
side of the fourth metatarsal, and not directly to the 
cuboid. The middle cuneiform is very small. There is a 
large sesamoid bone on the tibial side of the tarsus, articu- 
lating with the astragalus, navicular, and 
internal cuneiform. The tuberosity of 
the calcaneum is long and obliquely 
compressed. 

The functional digits in other Ro- 
dents may be five, as in the Rats, Por- 
cupines, and Squirrels ; or the hallux 
may be suppressed, as in the Hares; 
and occasionally the fifth digit is also 
wanting, reducing the number to three, 
as in the Capybara, Viscacha, and 
Agouti. The last-named animal has the 
three metatarsals elongated and closely 
pressed together, and all the digits with 
short subequal phalanges. A still further 
modification of the same type leads to 


the Jerboas (genus Dipus, see Fig. 117), iN ee Oe eee 
which at first sight much resembles that en as (Dipus 
of a bird. The three metatarsals are ‘ 
ankylosed together to form a single bone, which supports 
the three separate short digits, each with three phalanges. 
These alone are applied to the ground, the tarsus and long 
metatarsal segment being raised almost vertically. The 
hallux is wanting or rudimentary, but in some species there 
is a small fifth digit. 


318 THE HIND FOOT OR PES. [cHap. 


All the animals of the order UNGuLatTa are digitigrade, 
the heel being raised from the ground, and the metatarsal 
segment usually much elongated. ‘There is never any trace 
of a hallux. As in the corresponding segment of the fore 
limb, the pes is formed upon one or other of two distinct 
types, each characteristic of one of the sub-orders. 

In the Perissodactyla, the third digit is the largest, in the 
centre of the foot, and symmetrical in itself; the second 
and fourth are smaller, and nearly equal in length, but some- 
times quite rudimentary. A line drawn through the centre 
of the foot passes through the axis of the third digit, and 
the middle of the external cuneiform, navicular, and as- 
tragalus. The distal surface of the astragalus has a large 
articular surface for the navicular, and a very small one for 
the cuboid, which bone is of comparatively less importance 
than in the Artiodactyla, The calcaneum does not articu- 
late with the lower end of the fibula. 

The Rhinoceros (Fig. 118) and Tapir have all the usual 
bones of the tarsus well developed. The internal cuneiform 
has a curved process projecting backwards. The middle 
cuneiform (c?) is very small. The whole foot is compara- 
tively short and broad. The second and fourth toes are 
well developed, being nearly as long as the middle toe. The 
phalanges resemble those of the fore limb. In the Tapir 
the pes differs from the manus in wanting the fifth digit. 

In the Horse (Fig. 119), the middle toe is greatly 
enlarged, and the second and fourth reduced to slender 
styliform metatarsals, about three-fourths the length of the 
second, but supporting no phalanges. The navicular (7) 
and the external cuneiform (¢3) are very broad and flat. 
The cuboid (cé) is small, and the internal and middle 
cuneiform bones are small and united together. 

Various gradational stages between the complete tridac- 


= © as = 


Pee ee ee ee ee eee 


xIx.| UNGULATA. 319 


tyle foot of the Rhinoceros and the monodactyle foot of 
the Horse are met with in extinct species of the Perisso- 
dactyla. 


fa 
Ae it st (iy, 
NY DRT 
“Yi, i 
ie j Wy 


mill 
Fic. 118.—Dorsal surface of right tarsus Fic. 119 — Dorsal surface of right tarsus 
of Rhinoceros (AR/7xoceros sumatren- of Horse (Aguas cabadlus), 1. 


szs, }. 


In the Arvtiodacty/a the third and fourth digits are nearly 
equally developed, and their ungual phalanges are flattened 
on their contiguous sides, so that together they constitute a 
symmetrical form. ‘The second and fifth toes, when present, 
are also equal, but smaller than the others. A line drawn 
though the centre of the foot has on its tibial side the 
third digit and metatarsal, the external cuneiform, the 
navicular, and half the astragalus ; and on its fibular side 
the fourth digit and metatarsal, the cuboid and the ‘other 
half of the astragalus. The distal articular surface of the 


320 THE HIND FOOT On PES. | CHAP. 


astragalus is divided into two nearly equal facets, one for the 
navicular and one for the cuboid. ‘The calcaneum has an 
articular facet for the lower end of the fibula. 

In the Suzva (Fig. 120) all the tarsal bones are distinct. 
The four toes are well developed, and the metatarsals are 
usually distinct. The foot is relatively shortest and broadest 
in the Hippopotamus, the outer toes being nearly as long as 
the others, and the ungual phalanges very short, broad, 
and rounded in front. The Peccaries show a transition 


mit 


Nay hy Y : 
2 5 Spee \\\\ a hi 
LIL: jj — ml f Y VUZE 


Lien 


ml mie 
Fic. 120.—Dorsal surface of right tarsus Fic. 121.—Dorsal surface of right tarsus 
of Pig (Szs scrofa), 4. of Red Deer (Cervus elaphus), }. 


towards the ruminating sections of the order in the reduc- 
tion of the size of the outer toes and the confluence of the 
third and fourth metatarsals. On the hind foot the fifth 
digit is absent though the second is tolerably well developed. 


sane: | UNGULATA. 321 


In the Zy/ofoda the cuboid and navicular are distinct. 
There is no internal cuneiform. The second and fifth digits 
are entirely absent. The metatarsals of the third and 
fourth are united except at their lower extremity. The 
phalanges resemble those of the fore-foot. 

In the Zragudina the cuboid, navicular, and two outer 
cuneiforms are united to form a single bone. The third and 
fourth metatarsals are confluent. The second and fifth are 
complete, extending from the small digits up to the tarsus, 
but are very slender. 

In all the Pecora (Fig. 121) the cuboid (cd) and navicular 
(7) are united, as are the second and third cuneiform bones, 
and in some Deer (Cervudus and Pudi) these latter are further 
united with the cubo-navicular ; the first cuneiform is always 
distinct, though small.! The third and fourth metatarsals 
(m 111. and m Iv.) are united in the same manner as the 
metacarpals, and the phalanges of the digits are very similar 
to those of the manus. ‘The second and fifth metatarsals are 
always wanting ; the bones of the corresponding digits are 
absent in the Giraffe and most of the Oxen, Sheep, and 
Antelopes. In the Deer there are usually three small 
phalanges to each of these digits, not directly articulated 
with the rest of the skeleton. A large, oval sesamoid is 
commonly present in the piantar surface of the tarsus. 

The pes of the Hyrax closely resembles that of the 
Rhinoceros, but the ungual phalanx of the second digit is 
cleft almost to its base. 

In the PRogosciDEa the pes is short and broad, but 
smaller and more compressed than the manus, and in the 
more rudimentary condition of the two lateral digits shows 
a greater tendency to approach the Perissodactyle form. 

1 See Sir Victor Brooke, Proceedings of the Zoological Society, 1874, 
P. 34- 

Y 


322 THE HIND FOOT OR PES. [CHAP. 


The three middle toes have the usual number of bones, but 
the terminal phalanges are small and irregular in shape. 
The first and fifth toes have each one phalanx beyond the 
metatarsal. The astragalus is very flat, and has no articu- 
lation with the cuboid. ‘The internal cuneiform is produced 
distally, as is the corresponding bone of the manus. 

Order EpENTATA.—In the Sloths the pes much resembles 
the manus in its general characters, being long, very narrow, 
and curved, terminating in strong, compressed, pointed 
ungual phalanges, supporting hook-like claws. The tarsus 
is short ; the astragalus has a deep, cup-shaped cavity on its 
outer side, into which a conical projection of the lower end 
of the fibula is received. 

The appellation “‘Two-toed” applied to the genus C/o- 
lepus refers only to the anterior limb, for in the pes the 
three middle toes are functionally developed, and of nearly 
equal size in both the genera of the family. 

In Bradypus the tuber calcanet is long, compressed, and 
widened at the extremity. The tarsal bones have a great 
tendency to ankylosis. The first and fifth metatarsals are 
very rudimentary, and support no phalanges. ‘The proxi- 
_mal phalanges of the three middle digits are very short, and 
coalesce very early with the metatarsals, as in the corre- 
sponding part of the upper extremity. 

In Cholepus, the tuberosity of the calcaneum is very 
small. The tarsal bones remain distinct from one another. 
The proximal phalanges of the three middle digits are 
extremely short, but not ankylosed with the metatarsals. 
The first and fifth metatarsals are about three-fourths of the 
length of the others, flattened, and gradually diminishing in 
size to their free ends. | 

In nearly all the members of the Entomophagous section 
of the Edentata, the pes is much more normal in type, and 


' 


XIX. | MARSUPIALIA. 323 


adapted for plantigrade progression on the ground. It does 
not even present any modifications corresponding to those 
observed in the manus of the same animals. The normal 
number of tarsal bones, and the complete number of pha- 
langes, are always present in each digit. Of these the 
second and third are usually the longest, the fourth next, 
and the first and fifth shortest. 

The little prehensile-tailed Tree Anteater (Cycdothurus 
didactylus) has the pes modified into a climbing organ. 
The hallux is rudimentary, consisting of a metatarsal and 
one phalanx, concealed beneath the skin, but the four other 
toes are subequal and much curved, with long, pointed, 
compressed, ungual phalanges. The ¢uber calcanet is di- 
rected towards the plantar surface, and parallel with it, and 
extending to about double its length, is the greatly elongated 
sesamoid ossicle of the tibial side of the foot. These 
together support the prominent calcarine cushion to which 
the nails are opposed in climbing. 

In the MarsupraAiia, the hind foot is subject to great 
modifications, some of the genera presenting very striking 
deviations from the typical condition. 

The seven bones usually found in the Mammalian tarsus 
are always present and distinct from each other, but the 
astragalus is relatively smaller and more flattened than in 
Placental Mammals. In the climbing Marsupials espe- 
cially, the articular surface for the fibula, instead of being 
perpendicular to that for the lower end of the tibia, is 
almost in the same plane with it ; and in all, the “ head,” or 
portion of the bone which projects forwards to articulate 
with the navicular, is very slightly developed. 

In the American Opossums (Dide/phide), the foot is 
short and broad ; the hallux is stout, placed at right angles 
with, and opposable to, the other four digits ; it has a short, 

Y 2 


324 ITE FIND POOL OR PES. [CHAP. 


rounded terminal phalanx, which bears no nail. The other 
digits are subequal, and have compressed, pointed, curved, 
ungual phalanges. 

In the Dasyuride, the foot is comparatively narrow ; the 
second, third, fourth, and fifth toes are subequal; the hallux 
is either very small, and placed close to the others, or com- 
pletely suppressed, as in the Thylacine. 

In the Wombats (Phascolomyid@), the foot is short and 
‘broad ; the hallux is very short, with only one rounded 
phalanx, and divaricated from the other toes. These are 
nearly equal in length ; the fourth and fifth are stouter than 
the second and third, thus showing a slight tendency towards 
the condition met with in the next group. 

In all the remaining Marsupials a peculiar condition of 
the pes, called syndactylism, prevails. Whatever the con- 
dition of the other toes, or whatever the general form or 
function of the foot may be, the second and third meta- 
tarsals and digits are very slender, and enclosed nearly to 
their extremities in a common integument, so that they look 
externally like one small toe with two claws. 

In the Kangaroo (JZacropus) the whole foot (Fig. 122) is 
very long and narrow, and rests entirely on the ground in 
the ordinary position of the animal. The tarsal segment is 
short, the metatarsus very long. The cuboid is greatly 
developed, the navicular and the three cuneiform bones 
exceedingly small, in conformity with the condition of the 
digits they respectively support. There is a sesamoid on 
the plantar surface of the tarsus. The fourth metatarsal 
and digit are enormously developed, the fifth moderately 
so; the second and third are nearly as long as the fifth, but 
excessively attenuated. There is no rudiment of a hallux. 
The ungual phalanges are conical, pointed, slightly curved 
above, and flattened on the undez surface. ‘The whole foot 


mix MARSUPIALIA. 325 


is much compressed laterally, especially at its hinder part, 
so that the proximal ends of the second and third are 
thrown behind that of the great fourth metatarsal, and en- 
tirely concealed in a view of the dorsal surface of the foot. 

The ‘Tree-Kangaroos of New Guinea (Dendrolagus), 
which habitually live among the boughs of large trees, have 


Fea 
{hi MH 
Apa Be 
hy See wee” 
a | 
ts \ 
y i ie 
| ITT f 
| Vana 
Vv = 
\ 
¥ 
¥, IV 
Fic. 122.— Bones of right pes of Kan- Fic. 123.—Rones of right foot of Pha- 
garoo (JZacropus bennettiz), }. langer (Phalangista wulpina), #. 


the feet constructed on the same type, but shorter, and 
more laterally extended. 

In the leaf-eating, climbing Australian Opossums (Padan- 
gista, Fig. 123) and Koalas (Phascolarctos) the second and 
third toes are also very slender, but the fourth and fifth are 
more equal, especially in length, the foot is broad, and 
there is a strongly developed prehensile and opposable, 
though nailless, hallux. 


326 THE HIND FOOT OR: LES. [CHAP. 


The insect- and root-eating, ground-dwelling Bandicoots 
(Peramelide) differmg in many other respects from the 
Kangaroos, have their hind-foot constructed on exactly 
the same type as in AZacropus, even to the relative length - 
of the different digits, though there is often a rudiment of 
the metatarsal of the hallux. In one 
remarkable genus (Chwropus), already 
mentioned on account of the peculiar 
structure of the manus (see Fig. 104, 
p. 281), the same type is carried to a 
great extreme, the fourth toe (see Fig. 
124) remaining of a prodigious size 
and the fifth being reduced to even 
smaller dimensions than the second or 
third. 

MoNOTREMATA. —In both species 
the seven usual bones of the tarsus are 
complete and distinct,t and the five 
digits have the normal number of pha- 
langes. 

In the Ornithorhynchus the proximal | 
articular surface of the astragalus is 
Fic. 124. Benes of meht . Givided by -a deep groove into two 

pee ar cf distinct heads, one for the tibia, and 

the other for the fibula, the Jatter 
being the larger of the two; the inner side has a cup- 
shaped socket, into which fits an incurved conical process 
from the lower end of the tibia. The tuberosity of the cal- 
caneum is broad and bifid at the extremity, and directed 


' It has been stated that the cuboid in the Ornithorhynchus is divided 
into two bones, as in some reptiles, one supporting the fourth and the 
other the fifth metatarsal; but this is not the case in any specimen 
which I have examined. 


XIX.] ZONOTREMATA. 327 


not backwards, but towards the tibial side of the foot. In 
the male there is an additional, large, flat, curved ossicle, 
on the hinder and tibial side of the plantar aspect of the 
tarsus, articulated chiefly to the tibia, which supports the 
peculiar perforated horny spur characteristic of this sex, the 
function of which has not been discovered. There is also a 
small, rounded, supplementary ossicle, below the tibial edge 
of the tarsus, near the articulation between the astragalus and 
scaphoid. ‘The metatarsals increase in length from the first 
to the fifth. The phalanges are all rather long and slender. 
The four outer toes are nearly equal; the hallux is somewhat 
shorter. The ungual phalanges are compressed, slightly 
curved, and very sharp pointed. 

In the Echidna the astragalus is large, with an irregular, 
broad, rounded, proximal articular surface, not divided by 
a groove, and with a much less distinct fossa, for the in- 
ternal malleolus. The fwber calcaned is directed forwards, 
it is also bifid, and its external process is much longer than 
the other and curved towards the plantar surface of the 
foot. The spur of the male, and the ossicle which supports 
it, are much smaller than in the Ornithorhynchus. The 
metatarsals are shorter and broader ; they increase in length 
from the first to the fifth. The hallux is very short, and has 
a flattened, conical, ungual phalanx. The proximal and 
middle phalanges are all very short and broad. ‘The ungual 
phalanx of the second digit is extremely long and falcate, 
the others gradually diminish to the fifth. The ends of the 
toes are turned outwards and backwards in the ordinary 
position of the animal. 

The ungual phalanges of both extremities in the Mono- 
tremata have a deep median groove, near the base of the 
under surface, leading at its distal extremity into a foramen. 


CHAPTER XX. 


THE CORRESPONDENCE BETWEEN THE BONES OF THE ANTE- 
RIOR AND POSTERIOR EXTREMITY AND THE MODIFICA- 
‘LIONS OF THE POSITIONS OF THE LIMBS. 


Tuat a general correspondence exists in the plan of con- 
struction of the anterior and posterior extremity cannot fail 
to strike the most superficial observer, though to tollow out 
this correspondence into all its details has severely exercised 
the ingenuity of many an anatomist. 

It would be quite beside the character of the present 
work to give an historical account of the numerous and 
very various views which have been held upon this sub- 
ject,! but I propose to lay before the student in a con- 
censed form such portions of the general outcome of these 
researches as appear to be most satisfactorily established, 
premising, however, that all the statements hereinafter to 
be made have not yet met with universal assent.” 


1 For the bibliography of this question, see Mivart ‘‘ On some Points 
in the Anatomy of Echidna hystrix” (Linn. Soc. Trans. xxv. 1866) ; 
and Rolleston ‘‘ On the Homologies of certain Muscles connected with 
the Shoulder Joint” (/d¢d. xxvi. 1869). See also Humphry’s ‘‘ Ob- 
servations in Myology,” 1872. 

2 For an exposition of the very opposite hypothesis of ‘* Antero- 
posterior Symmetry,” see Jeffries Wyman ‘‘On Symmetry and Homo- 
logy in Limbs” (Proc. Boston Soc. Nat. Hist., June, 1867, p. 277); and 
the elaborate series of papers by Dr. Elliott Cones, published in the 
Medical Record (New York) for 1870. 


CHAP. XX. ] LHE CORRESPONDENCE, &c. 329 


In the first place, it is perfectly obvious that the fore and 
hind limbs have each a similar division into four main seg- 
ments; the shoulder girdle, the arm, the fore-arm, and the 
manus of the one representing respectively the pelvic girdle, 
the thigh, the leg, and the pes of the other. 

To proceed to further details, it is necessary to place the 
limbs (at least in imagination) in an exactly corresponding 
position—one, in fact, which is often impossible in the adult 
animal on account of the modifications of the articular sur- 
faces to suit the posture best adapted for the habits and 
mode of life of the individual, but which is the position of 
all limbs when they first appear as bud-like processes from 
the side of the body of the embryo. In this position the 
limbs are extended at right angles to the axis of the trunk 
and parallel to each other, as in Fig. 125, aand B. There 
is then to each lhmb a superior or dorsal surface (turned 
towards the observer in the figure), an inferior or ventral 
surface, and an anterior and a posterior edge. These last 
are called by Professor Huxley preaxzal and postaxial (in 
reference to the axis of the limb itself) to avoid the con- 
fusion with axterior and posterior in the modified positions 
they assume in Man and various animals. In the figures 
the preaxial side is left light, and the postaxial side is 
shaded. 

The dorsal surface of the anterior extremity includes the 
back of the hand and the extensor surface of the fore-arm 
and arm. ‘The dorsal surface of the posterior extremity 
includes the dorsum of the foot, front of the leg, and the 
extensor surface of the thigh. The preaxial border of the 
anterior extremity has in it the pollex, the radius, the 
condyle commonly called “ external,” and the greater tuber- 
osity. ‘The preaxial border of the posterior extremity in- 
cludes the hallux, the tibia, the condyle commonly called 


ios) 


Lo>) 


fo) THE CORRESPONDENCE BETWEEN THE Cure: 


Fic. 125.—Diagrammatic representation of the positions of the limbs of Mammalia. 


The preaxial border is left light, the postaxial border shaded, in all the figures. 
Limbs of the right side are represented in all cases. A dorsal aspect of the 
anterior extremity in its primitive unmodified position; gé glenoid border of the 
scapula ; s spine; cé coracoid border ; ssf subscapular fossa ; Af postscapular (in- 
fraspinal) fossa ; c coracoid ; # humerus; g¢ greater, radial, or preaxial wuberosity ; 
é¢ lesser, ulnar, or postaxial tuberosity; ec external (in the modified position), 
radial, or preaxial condyle; zc internal, ulnar, or postaxial condyle; 7 radius, 
z ulna; 1 pollex; v fifth digit. dorsal aspect of the posterior extremity in the 
same position; ad acetabular border of the ilium; Zé pubic border; 26 ischial 
border; gs gluteal surface: zs iliac surface; z ischium; # pubis ;_f femur; Z¢ lesser, 
tibial, or preaxial trochanter ; g¢ greater, fibular, or postaxial trochanter; zc in- 
ternal (in the modified position), tibial, or preaxial condyle ; ec external, fibular, 
or postaxial condyle; ¢ tibia; / fibula; 1 hallux; v fifth digit; c the anterior 
extremity, with the humerus in the same position, but the eibow- and wrist-joints 
bent; D the posterior extremity in the same position. 


“‘ internal,” and the lesser trochanter. All these parts, then, 
should be regarded as serially homologous. 


a 


exe ANTERIOR AMD. POSTERIOR EXTREMITY. 


(oS) 
iS) 
Ln | 


Fic. 126.—Diagrammatic representation of the positions of the limbs of Mammalia 
continued. the anterior extremity with the same flexures as in Cc, but with the 
whole limb rotated backwards. The preaxial side is external. ‘The letters as 
before. rF the posterior extremity, with the joints bent, and the whole limb rotated 
forwards, as in the ordinary position of quadruped Mammals. ‘The postaxial side 
is external. G the humerus in the same position as in E, but the fore-arm r tated, 
as in the ordinary position of quadruped Mammals. Whilst the preaxial side of 
the humerus remains external, the postaxial side of the manus is now external. 
H the anterior extremity of a Cetacean (Hyferoodor), dorsal surface. 1 the pos- 
terior extremity of a Seal, dorsal surface. 


Leaving for the present the shoulder and pelvic girdles 
out of consideration, we will next consider the adaptive 
changes which take place in the segments of the limb 
proper in various animals. These will be best understood 
by dividing them into stages (all of which are represented 
in the diagram), though it is not meant to imply that the 


332 THE CORRESPONDENCE BETWEEN THE [cHap. 


limbs actually go through so many distinct phases in the 
course of development, as all the various modifications from 
the primitive to the most adaptive positions may take place 
gradually and even simultaneously. 

In what may be considered the first stage of modification 
(Figs. c and D), each segment of the limb is simply bent 
upon the one above it. The proximal segments (humerus 
and femur) remain unchanged in position, the dorsal surface 
still looking upwards, and the ventral surface downwards ; 
the middle segment is bent downwards, so that its ventral 
surface faces inwards and its dorsal surface outwards ; and the 
joints between these segments (elbow and knee) form pro- 
minent angular projections. The third segment being bent 
to a greater or less degree in the opposite direction to the 
middle one, retains much of its primitive position, the dor- 
sal surface being directed upwards and the ends of the digits 
pointing outwards. The relations of the preaxial and postaxial 
borders of the limb are unchanged. No Mammal habitually 
carries its hmbs in this position, although the climbing Ga/eo- 
pithecus and the Sloths are not far from it. It is, however, 
very nearly the normal position of some Reptiles, especially 
the Tortoises, though it is ill adapted for anything but a 
very slow and clumsy mode of progression. 

The next change, and one which takes place at a very 
early period in embryonic life, and which is one of the most 
essential in giving the characteristic conformation of the 
extremities of the higher Vertebrates, is a rotation of the 
whole limb from the proximal end, though in opposite 
directions in each case. 

The anterior extremity (see Fig. E) is rotated from the 
shoulder, through nearly a quarter of a circle, backwards, so 
that the humerus, instead of being at a right angle to the axis 
of the trunk, is nearly para!lel with it, the elbow points back- 


Kx.|.. AVZZAIOR AND POSTERIOR EXTREMITY. s28 


wards, the preaxial side is outwards, and the postaxial side 
towards the middle line of the body, and as long as the 
radius and ulna retain their primitive paraliel position, the 
manus is placed with the ends of the digits directed back- 
wards, the preaxial side being external. 

The hind limb (see Fig. F) is, at the same time, rotated 
from the hip to the same extent forwards, so that the femur 
is also nearly parallel to the axis of the body, but with the 
knee projecting forwards ; the preaxial side is inwards and 
the postaxial side outwards ; the tibia and fibula are parallel, 
the former internal and the latter external ; the foot has the 
ends of the digits directed forwards, the hallux or preaxial 
digit is on the inner, and the fifth or most postaxial digit 
is on the outer, side. 

In this position the hind limb remains, subject only to 

minor modifications, in nearly all terrestrial Mammals; but 
the Walrus, and to a certain extent the Sea-Lions, alone 
carry the fore limb as described above without further 
modification. 
_ The next stage, affecting the fore limb alone, consists in 
the rotation of the lower end of the radius around the ulna, 
which brings the distal extremity of the manus round from 
the back to the front of the limb (see Fig. c). In most 
Mammals the limb is permanently fixed in this position, 
and the bones of the fore-arm become greatly modified in 
consequence, as described in Chapter XV. It will now be 
understood how, though the outer side of the humerus 
corresponds with the inner side of the femur, in ordinary 
quadruped progression, yet the outer side of the manus 
corresponds with the outer and not the inner side of 
the pes. 

To these general conditions there are certain modifications 
met with in some animals, and certain exceptions in others. 


334 LHE CORRESPONDENCE BETWEEN THE  |CuAE: 


The modifications with regard to the anterior extremity 
are that the humerus may be quite horizontal, or its distal 
end may incline upwards, or, as is much more frequently the 
case, it may incline somewhat downwards, so that the dorsal 
surface is posterior and the ventral surface anterior ; the fore- 
arm in the ordinary resting position may be quite vertical, 
or inclined with its upper end backwards; the whole of the 
manus may rest entirely on the ground, as in the so-called 
‘“‘nlantigrade” or rather ‘‘palmigrade” animals, or the 
proximal part, the tarsus and metatarsus, may be raised and 
placed more or less vertically, the limb resting either on all 
or only on the terminal phalanges, according to the com- 
pleteness of the ‘“digitigrade” mode of progression. 

Similar modifications occur in the hind limb. The 
femur is usually inclined with its distal end downwards, so 
that the dorsal or ‘“‘extensor” surface is anterior, and the - 
ventral or ‘ flexor” surface posterior. In the Elephants it 
is very nearly vertical. In most animals which occasionally 
assume the upright position, as the Kangaroos and some 
Rodents, the femur is ordinarily inclined upwards at its 
distal extremity, so that the knee is above the acetabulum, 
and the pelvis slung as it were between the two hind limbs. 
In Man, on the other hand, in standing or walking the 
femur is nearly vertical with the distal ends downwards, and 
the pelvis is supported on the top of the limbs. 

The positions of the limbs which are quite exceptiona 
are those of certain aquatic animals. 

In the Cetacea (Fig. H) none of the segments of the 
anterior limb undergo any deflection from the primitive 
straight condition, nor is there any rctation of the: bones of 
the forearm. The only changes which take place are a partial 
rotation backwards from the shoulder, and a slight turning 
downwards of the preaxial border. In the Sirenia and the 


xx.| . ANTERIOR AND POSTERIOR EXTREMITY. 335 


Seals, there 1s a slight bend at the elbow and the wrist, 
but little or no rotation of the fore-arm. 

In the hind limb of the Seal (Fig. 1) there is very little 
flexure at the joints, and the whole limb is turned backwards 
instead of forwards from the hip, and at the same time 
rotated on its axis, so that the preaxial border becomes 
turned downwards. ‘The skeleton of this limb, therefore, 
and that of the fore limb of the Cetacean, being retained 
normally in almost exactly similar positions, are well adapted 
for demonstrating the correspondence between the re- 
spective: bones of which they are composed (see Figs. 
H and 1). 

The necessity of the modifications in the direction of the 
axes of the heads of the humerus and femur spoken of pre- 
viously will easily be understood by a consideration of the 
relative positions that these bones are adapted to assume. 
Thus the axis of the head of the humerus in the majority of 
Mammals is inclined towards the postaxial side of the shaft 
of the bone, while that of the femur is inclined towards 
its preaxial side. 

Hitherto nothing has been said about the shoulder and 
pelvic girdle, because the correspondence of their parts is 
not so easily explained, nor so generally recognised, as that 
of the segments of the limb proper. The following view 
appears to be, of those yet suggested, the most probable. 

It has been already shown (Chapters XIV. and XVII.) 
that the lateral half of each girdle consists primarily of a 
bar or rod placed vertically, and divided into an upper and 
a lower segment, the point of attachment of the limb being 
_ close to the junction of these two segments. The upper 
segment in the fore limb is the scapula, in the hind limb the 
ilium ; the lower segment in the fore limb is the coracoid, 
in the hind limb the ischium and pubis. 


336 THE CORRESPONDENCE BETWEEN THE {[cuar. 


In every Mammal both scapula and illum may be re- 
solved into bars or rods of three-sided or prismatic form. 
The two extremities of each bar are placed, as regards the 


general position of the trunk, dorsally and ventrally. The 


dorsal or upper extremity is capped by the suprascapular 


epiphysis in the shoulder girdle, and by the corresponding 
supra-iliac epiphysis in the pelvic girdle. The ventral 
or inferior extremity enters into the formation of the 
glenoid or the acetabular articular cavity, as the casé 
may be, and joins the coracoid or the ischial element of 


the girdle. te 


three surfaces and three borders. In what may be, at least 
. . . . . . 4 . 
theoretically, considered their primary position, the surfaces 


of each bar are—(1) Inner or vertebral, turned towards the 
vertebral column; (2) Preaxial, corresponding to the preaxial | 
line of the limb (Fig. 125, A Af, B zs); (3) Postaxial, cor- » 
responding to the postaxial line of the limb (a ssf, B gs). ‘The. 
borders are—(1) External, in a line with the middle of the 
dorsal surface of the limb, and terminating below at the. 
upper margin of the glenoid or acetabular cavity (A gd, B ab); 


(2) antero-internal, terminating below in the acromion or 


in the pubis (a s, B £2); (3) postero-internal, terminating . 


below in the coracoid, or the ischium, as the case may be 
(A cb, B 20). : 

The correspondence between these parts of the scapula 
and ilium will be ‘better understood by placing, them in 
a tabular form, the middle column showing the names 
expressed in the generalized or ideal condition applicable 
to both in their primitive condition, and the column at each 
side giving the special terms applied to each part in its 
variously modified forms. 


- 
. 
‘ 
. 


r-* 


Se 


The bar, supposed to be in a nearly vertical position, has xo 


* 
a 


63 
¥ 


- 


eel ANTERIOR AND POSTERIOR. £LATREMITY. 337 
SURFACES: 
SCAPULA. IDEAL. PELVIS. 
i Prescapular fossa. I. Vertebral. Sacral surface. 
; ' Supraspinous fossa. Inner surface of ilium, 
. behind linea arcuata 
interna, including the 
an articular surface for 
’ the sacrum, and the 
.. portion of the bone 
bab above and below this. 
vee. 
| Postscapular fossa. 2. Preaxial. Iliac surface. 
| Infraspinous fossa. Internal iliac fossa. 
Subscapular fossa. 3. Postaxial. _ Gluteal surface. 
- alls : 7 ; 
? v 
BORDERS. 
SCAPULA. | IDEAL. PELVIS. 
1 iw os | » 
3 _| Glenoid border. | 1. External. Acetabular border. 
Be Posterior border in Anterior porder. 
i most animals. 
q Axillary border in 
&, Man. 
: : Spine. 2. Antero-internal. | Pub‘c border. — 
y! Linea arcuata interna, 
Coracoid border. 3. Postero-internal. | Ischial border. 
Anterior border in Posterior border. 
most animals. 
Superior border in 
Man. 


As the humerus in ordinary quadruped Mammals is 
* rotated backwards from its primitive position, and the femur 


L 


"a 


~ 


338 THE CORRESPONDENCE BETWEEN THE [cuap. 


is rotated forwards, so that the preaxial side of the first 
becomes external, and the really corresponding side of the 
other becomes internal, so it is with the scapula and ilium. 
Each has undergone a rotation on its own axis, through 
nearly a quarter of a circle, and in the opposite direction 
(see Fig. 126, E and F), so that the inner surface of the one 
comes to correspond with the outer surface of the other, 
the anterior border of the one with the posterior border of 
the other. The long axis of each is also differently inclined, 
the upper end of the’scapula leaning backwards, while that 
of the ilium is inclined forwards, which makes the resem- 
biance between them seem still more obscure. 

These views are considerably strengthened by a con- 
sideration of the disposition of the muscles connected with 
the various bones in question." 

The principal differences between the shoulder and pelvic 
girdle of the Mammalia are two :—(1) The rudimentary con- 
dition of the inferior or ventral section of the girdle (the 
coracoid) in the former, as compared with the vast deve- 
lopment of the corresponding part of the lower extremity ; 
(2) the free condition of the anterior as compared with the 
posterior girdle. It is neither attached to the vertebral 
column above, nor does it (except in the Monotremata) join 
the opposite part in the middle line below. ‘To compensate 
for this, a clavicle is superadded to the anterior girdle in 
many Mammals, for which there is no exact homologue in 
the lower extremity. 

It has been shown in Chapters XVI. and XIX. that 
the terminal segments of each limb present a remarkable 
general correspondence with certain constant differences. 

1 See ‘On the Correspondence between the Parts composing the 


Shoulder and the Pelvic Girdle of the Mammalia” (fournal of Anatomy 
and Physiology, vol. iv. p. 239, 1870). 


s 


xx.] ANTERIOR AND POSTERIOR EXTREMITY. 339 


J 


There can be no question but that the carpus and tarsus, 
the metacarpus and metatarsus, and the. various digits 
beginning at the pollex in the one, and the hallux in the 
other, are really homologous ; the circumstance of the con- 
stant absence of one of the bones of the preaxial digit in 
both fore and hind limbs is most significant. 

In the carpus and tarsus, the serial homology of the four 
bones of the distal row in their respective order is generally 
admitted, but with the other bones there is still some differ- 
ence of opinion. Gegenbaur has, however, given good 
reasons,! derived chiefly from the results of tracing both 
limbs back to their less modified condition in Reptiles and 
Amphibia, for considering the astragalus as equivalent to 
the scaphoid and lunar united, or the scapho-lunar bone of 
the Carnivora &c.; the calcaneum as representing the 
cuneiform, and not, as often supposed, the cuneiform and 
the pisiform (the latter being only a sesamoid); and the 
navicular of the foot as representing the os centrale, found 
only occasionally in the manus of Mammals. 


1 “* Untersuchungen zur Vergleichenden Anatomie,” 1**s Heft, Carpus 
und Tarsus, 1864. 


4 


od 


Ee. 


A. 


AcuT! (Dasyfrocta), 77, 160, 250, 265, 317. 


A lces (Elk), 174. 

Anchitherturnz, 268. 

Anoplotherium, 67, 2. 

Anteater (Wyrimecophaga), 41, 55, 56, 57; 
62, 83, 84, 94, 205, 206, 234, 277, 306. 

Antelope, 173. 321- 

Antilocapra (Prongbuck), 270. 

Ape, 18, 24, 25, 48, 66, 247; see also 
Szmzina. 

Arctomys (Marmot), 157, 160, 265. 

Armadillo (Dasypus), 7, 40, 56, 58, 62, 69, 
ae 94, 207, 235, 253, 257, 278, 279, 294, 

06. 


3 
Artiodactyla, 3, 24, 51, 92, 161, 169, 268, 
303, 318, 319. 


- Ateles (Spider Monkey), 47. 66, 247, 260. 


Aye-Aye (Chzvomys). 247, 261, 314. 


aB: 
BaBoon (Cynocephalus), 138, 139, 140, 260, 


209- 

Balena (Whale), 37, 38, 80, 81, 92, 93, 196, 
197, 198, 232, 272, 294. 305. 

Lalenopterea (Fin Whale), 38, 39, 52, 81, 
92, 93, 196, 198, 232, 252, 272, 294, 305- 

Bandicoot (Peramzeles), 42, 43, 59, 237, 280, 
281, 326. 

Bat, see CHIROPTERA. 

Bathyergus, 157. 

Bear (Ursus), 49, 62, 66, 144, 146, 248, 261, 
290, 301, 314. 

Beaver (Castor), 21, 62, 67, 157, 158, 160, 
229, 230, 250, 265, 201, 302, 317- 

Beluga, 40, 274. 

Bradypus, 41, 55, 85, 209, 236, 237, 252, 
276, 277, 322; see also Sloth. 


ee 
CACHALOT (Physeter), 49, 52, 53, 54, 795 
80, 93, 94, 193, 194, 195, 232, 274: 
Camel, 35, 41, OI, 174, 250) 251, 269, 270, 


292. 
Capybara (Hydrocherus), 33, 67 77) 156, 
158, 160, 265, 317. 


CARNIVORA, 3, 24, 31, 49, 62, 66, 75, 91, 
230, 248, 261, 289, 301, 310, 314. 

Castor (Beaver), 21, 62, 67, 144, 150, 1575 
158. 229, 230, 265, 291, 302- 

Canide@, 91, 231, 248, 314, 317- 

Canis (Dog), 15. 22, 31, 32, 49. 75, 99-127). 
144, 150, 223, 248, 261, 287, 301, 314. 

Capromys, 50, 265. 

Cat (Felis), 49, 63, 144, 147, 150, 262, 314. 

Cavia (Guinea-Pig), 67, 229, 291. 

Cebid@, 138-141, 245. 

Cebus, 1309. 

Centetes, 32, 50, 66, 152, 249, 263, 302. 

Centetid@, 152. 

Cercopithecus, 142. 

Cervide, 172. 

Cervus (Deer), 34, 78, 173, 233, 248, 269, 
270, 304, 320, 321. 

CETACEA, 3. 25, 37, 52, 54, 62, 68, 79. 92, 
181, 185, 231, 244, 251, 257, 271, 283, 293, 
304, 334, 335. - 

Cheetah, 150 

Chelydra, 255. 

Chinchilla, 160. 

Chimpanzee (7voglodytes), 31, 47, 48, 60, 
75, 91, 138, 139, 227, 260, 289, 301. 

Chirvomys (Aye-Aye), 247, 261, 314. 

CHIROPTERA, 3, 33, 50, 66, 77, 153, 229, 
249. 264, 291, 302, 316. 

Chlamydophorus, 69. 

Cheropus, 280, 281, 282, 325, 320. 

Cholepus, 10, 24, 41, 55, 85, 90, 210, 236, 
252, 276, 322. 

Chrysochloris, 50, 153, 227, 249, 264. 

Calogenys (Paca), 158, 160. 

Colobus, 260. 

Condylura, 227 

Coypu (Al yopotamus), 156, 229, 250. 

Crocodile, 60. 

Cyclothurus, 55, 56, 69, 84, 94, 207, 235, 
Bier, rte). 

Cynocephalus (Baboon), 138, 139, 140, 142, 
260, 289 

Cystophora, 49, 151. 


15 


Dasyprocta (Aguti), 77, 160, 265, 317. 

Dasypus (Armadillo), 7, 41, 56, 58, 62, 69, 
ap 94, 207, 235, 253, 257, 278, 279, 294, 
306. 


342 INDEX, 


Dasyure (Dasyurus), 215, 253, 280, 295, 
296, 324. 

Deer (Cervus), 34, 78, 172, 173, 233, 248) 
269, 270, 304, 320, 521. 

Delphinid@e, 40, 193. 

Delphinus (Dolphin), 40, 52, 79, 91, 231, 
275, 294. 

Dendrolagus, 323. 

Desniodus, 66 

DIDELPHIA, 4. 

Didelphys (Opossum), 42, 43, 59, 70 215, 
237, 280, 295, 296, 323. 

Dipus (Jerboa), 33, 160, 317. 

Dog (Cats), 15, 22, 31, 32, 49, 62, 75, 96, 
127, 144, 150, 223, 248, 261, 287, 301, 314. 

Dolphin (Deiphinus), 40, 52, 53, 79, 93> 
231, 275, 294. 

Dugong (Hadicore), 36, 51, 82, 204, 252, 
275, 293: 


E. 


Echidna, 20, 43, 59, 62, 70, 86, 95, 217, 
218, 238, 282, 307, 327. 

ECENTATA, 25, 33, 40, 55, 62, 69, 82, 94, 
204, 234, 252, 276, 286, 294, 298, 305, 


321. 
Elephant (Zefhas), 36, 51, 61, 67, 92, 127; 
180, I8t, 234, 266;8292, 298, 304, 327, 


334. 
Elephant Seal (Alacrorhinus), 258, 315, 


316. 

Elk (Alces), 174. 

Enhydris (Sea Otter), 298, 315. 

Eguus (Horse), 35. 51, 77: 79s 925 164, 233, 
250, 251, 207, 263, 393, 318, 319- 

Ericulus, 302. 

Erinaceus (Hedgehog), 50, 66, 76, 152, 
249, 263, 290, 301. 


F. 


Felid@, 32, 49, 91, (47, 149, 231, 248, 314. 

Felis (Cat), 49, 63, 147, 149, 262, 314. 

Fiber, 50. 

Fin Whale (Balenoptera), 38, 39, 52, 81, 
92, G3, 196, 198, 232, 252, 272, 294, 305. 

Fissipedia, 3. 


G. 


Galago, 48, 314. 

Galeopithecus, 32, 50, 15%, 229, 249, 563, 
264, 302, 332. 

Gibbon (Hylobates), 47, 48, 75, 138. 

Giraffe, 35, 78, 233, 270, 292, 321. 

Globicephalus, 40, 53, 185, 187, 190, 273, 


274. 

Glyptodon, 58. 

Gorilla (Tvoglodytes}, =1, 47, 48, 61, 75,91, 
138, 139, 140, 227, 247, 260, 289, 301. 


Grampus (Orca), 40, 274 275. 
Guinea Pig (Cazvia), 67, 229, 29% 
Gymnura, 66, 152, 263. 


ae 
FHlalicore (Dugong), 36, 51, 82, 204, 252, 


275, 293- 

Flalithertum, 293, 305- 

Hapale, 247. 

Hlapalida@, 141. 

Hare (Lepus),.14, 33, 50, 67, 77, 157, 161, 
220, 250, 205, 201, 302, 317- 

Hedgehog (Erinaceus), 50, 66, 76, 152, 
249, 263, 290, 301. 

flipparion, 268. 

Hippopotamus, 35, 79, 176, 234, 251, 269, 
803,0920: 

Horse (49225), 35, 5%; 77> 79, 92, 164. 165, 
223, 250, 251, 267, 268, 303, 318, 319. 

Hyzna, 49, 150, 261, 29v. 

Hyenide, 91, 248, 314. 

Hydrocherus (Capybara), 33, 67, 77, 156, 
158, 160, 265. 

Hylobates (Gibbon), 47, 75, 138. 

fyontoschus, 270. 

flyperoodon, 40, 52, 53: 92, 94, 193, 194, 
274, 331- 

Flypsiprymnus, 215, 280. 

HyYRACOIDEA 4, 177. 

Hyrax, 4, 10, 24, 51, 67; 92, 177, 234, 251, 
265, 266, 304, 32I. 

Hystrix (Porcupine), 67, 156, 157, 159, 
230, 317. 


16 


Inia, 40, 52, 274. 
INSECTIVORA, 3, 24, 32, 49, 66, 76, I50, 
227, 249, 203, 290, 301, 316. 


ii. 
JERBOA (Digus), 33, 160, 3176 


‘ Ke: 


KANGAROO (Macropus), 42, 59, 70, 215, 
216, 280, 295, 296, 324, 325, 334. 

Koala ( Phascolarctos), 42, 59, 7°, 94, 215, 
306, 325. 

Kogia, 94, 195+ 


L. 


Lagostomus (Viscacha), 157, 159, 317- 

Lagothrix, 30, 49, 142. 

Lemur, 48, 143, 247, 260, 289, 301, 314. 

Lemurina, 3, 31, 48, 62, 66, 91, 143, 144, 
I5I, 260, 313. 


> 


INDEX. 343 


Leopard, 63, 64, 150. 

Lepus, 33, 265; see also Hare and Rabbit. 
Lion, 150, 262. 

Diamar, 355174, 271- 

Loncheres, 50. 

Lophiomys, 150. 

Loris, 48, 289. 

Lynx, 66, 150 


M. 


Macrauchenia, 35. 

Macropus (Kangaroo), 42, 59, 68, 70, 215, 
216, 280, 295, 296, 324, 325, 334- 

Macrorhinus, 258, 315, 316. 

Macroscelides, 50, 151, 249, 290. 

Man, 18, 20, 25, 26, 44, 61, 65, 73, 89, 90, 
128-137, 226, 245, 243, 258, 286, 298, 301, 
310, 311, 334- 

Manati (Manxatus), 3, 21, 36, 51, 82, 92, 
199, 252, 275, 293- 

Manis (Pangolin!, 25, 41, 55, 58, 60, 69, 
83, 208, 234, 276, 277. 

Marmot (A7cfonzys), 156, 157, 160, 265. 

MARSUPIALIA, 4, 24, 25, 42, 59, 62, 70, 86, 
94, 212, 237, 253, 280, 295, 306, 323. 

Megaderiia, 155. 

Megaptera, 40, 93, 232, 252, 305- 

Megatheriunt, 56, 230. 

Meles, 49. 

Mellivora, 49 

Menopoma, 60. 

Mephitis, 49 

Mole ( 7adfa), 32, 50, 69, 76, 77, 152, 222, 
227, 249, 203, 264, 291, 316. 

MOoONODELPHIA, 2 

Monodon (Narwhal), 40, 274. 

MOoNOTREMATA, 5, 43, 59, 62, 70, 85, 86, 
88, 95, 216, 237, 253, 282, 296, 298, 306, 
326. 

ATormops, 155. 

Moschus, 67. 

Mus (Rat), 157, 158, 265, 317. 

Mustela (Weasel), 49, 147- 

Mustelide, 91, 146, 248, 314. 

Mycetes, 30, 31, 49, 75, 138, 139) 142, 143, 
24 

Made 32, 316. 

Myopotamus (Coypu), 156, 229, 250. 

Myrmecophaga (Anteater), 41, 55, 56, 57, 
62, 83, 84, 94, 205, 206, 234, .277, 306. 

Mystacoceti, 3, 37, 81, 195- 


N. 
NaARWHAL (Monodon), 40, 274. 
Nasua, 49. 
Nycticebus, 48. 

O. 


Odontoceti, 3, 40, 79, 93, 185, 231, 272, 
294, 305. 

Opossum (Didelphys), 43, 59, 7°, 215, 2375 
280, 295, 296, 323. 


Orang, (Sima), 31, 47, 48, 61, 75, 91, 
138, 139, 140, 259, 261, 298, 312. 

Orca (Grampus), 40, 274, 275. 

ORNITHODELPHIA, 5, 43- 

Ornithorhynchus, 14, 43, 44, 509, 62, 71, 
85, 86, 95, 219, 238, 239, 282, 307, 326. 

Orycteropus, 41, 55, 58, 62, 69, 83, 94, 
209, 224, 277, 294, 295, 306. 

Otaria (Sea Lion), 49, 151, 231, 316, 333. 

Otariide, 150, 262, 316. 

Ox Or, 2725 270,032r- 


P. 


Paca (Celogenys), 158, 160. 

Paleotherium, 268. 

Pangolin (A7anzs), 25, 41, 55, 58, 69, 83, 
208, 234, 276, 277. 

Paradoxurus, 60. 

Peccari, 232, 269, 320. 

Pecora, 4, 33, 174, 232; 291, 303, 321. 

Pedetes, 67. 159, 160. 

Perameles (Bandicoot), 42, 43, 59, 237, 
280, 281, 326. 

Perissodactyla, 3, 24, 51, 92, 162, 168, 
268, 292, 298, 303, 318. 

Perodicticus (Potto), 49, 260, 289, 314. 

Petrodromus, 249, 316. 

Phalangista, 42, 70, 280, 306, 325. 

Phascolarctos (Koala), 42, 59, 70, 94, 215, 
306, 325. 

Phascolonzys (Wombat), 42, 59, 62, 70, 95, 
210, 237, 242,253, 280, 295, 324: 

Phoca (Seal), 49, 66, 150, 231, 249, 263, 
290, 298, 301, 315, 331, 335. 

Phocena (Porpoise), 40, 65, 79, 93. | 

Physeter (Sperm Whale or Cachalot), 40, 
52, 53> 54, 79, 93, 94, 193, 194, 232, 274. 

Pig (Szs), 21, 35, 78, 79, 80, 174, 233, 
251, 269, 292, 303, 320 ; 

Pinnipedia, 3, 76, 91, 231, 248, 262. 

Pipistrellus, 229. 

Platanista, 37, 40. 193, 232, 239, 274. 

Pontoporia, 40, 193. 

Porcupine (A/ystvix), 67, 156, 157, 159, 
T60:) 2305 SE7e 

Porpoise (Phocena), 40, 65, 79, 93 

Potamogale, 32, 66, 229, 264. 

Potto (Perodicticus), 49, 260, 289, 314. 

PRIMATES, 3, 26, 46, 74, 90, 225, 245, 
259, 284, 301, 310, 3IT. 

Priodontes, 69, 84, 95, 235, 272, 280. 

PROBOSCIDEA, 4, 36, 79. 251, 321. 

Procyon, 49. 

Procyonide, 91, 146, 248, 314. 

Prongbuck (A xtilocapra), 270. 

Pseudorca, 40. 

Pteropits, 77, 153-155, 229, 264, 302. 

Puma, £50. 


R. 


RABBIT, 229, 230; see also Lepus. 
Rat (A7us), 157, 160, 265, 317.- 


344 


Rhinoceros, 35, 51, 79, 92, 166, 250, 251, 
267, 268, 302) 303, 318, 319. 

Rhynchocyon, 50, 66, 76, 151, 249, 264, 
290, 316. 

Rhytina, 36. 

RODENTIA, 4, 24, 23, 50, 62, 67, 77, 155, 
229, 250, 264, 291, 298, 302, 310, 317. 
Rorqual (Balenoptera), 38, 39, 52, 81, 92, 
93, 196, 198, 232, 252, 272, 294, 305. 

Ruminantia, 4, 77- 


Satga, 173. 

Sainitris, 138. 

Sauropsida, 44. 

Scalops, 227. 

Sciurus (Squirrel), 157-161, 265, 3 

Seal (Poca), 49, 66, 150, 231, ae 263, 
290, 298, 301, 315, 331, 335- 

Sea-Lion (Ofaria), 49, 151, 231, 316, 333- 

Sea-Otter [Exhydris), 298, 315. 

Semmnopithecus, 66. 

Sheep, 61, 169, 270, 284, 321. 

Shrew (Sorex), 32, 50, 76, 153, 228, 264. 

Simia (Orang), 31, 47, 48, 61, 74, 91, 138, 
139, 140. 259, 261, 298, 312. 

Sz1ina, 66, 90, 137 et seg., 143, 
289, 312. 

SIRENIA, 3, 18, 36, 51, 62, 68. 82, g2, 198, 
232, 252, 275, 283, 293, 305- 

Sloth; 4, 55) 56, Gx, 62, G9, 85, 90, 94. 
209, 224, 236, 252, 276, 204, 298, 306, 
Boo) 380. 232 See also Lradypus and 
Chole pus. 

Solenodon, 66, 262, 302. 

Sorex (Shrew), 32, 50, 

Svricid@, 50, 22%. 

Sperm-Whale (P/yseter), 40, 52 
80, 93, 94, 193, To4. 232, 274. 

Spider Monkey (A Ze/es), 47. 66, 247, 260. 

Squirrel (Sczz7-ws), 156, 157, 160, 205, 317. 

Suz2a, 3, 35, 269, 320. 

Sus (Pig), 21, 35, 78, 79, 174, 233, 251, 
269, 292, 303, 320. 


144, 247, 


70, (E53; 2205 204: 


53> 54, 


Ty. 


Talpa (Mole), 32, 50, 76, 77, 152, 222, 
227, 249, 264, 291, 316. 


LONDON : 


INDEX. 


Tapir (7apirus), 35, 5%, 77; 79) 925 167, 
234, 251, 267, 303,. 318. 

Tarsipes, 216. 

Tarsius, 144, 289, 313. 314. 

Tatusia, 280. 

Thylacine (7/ylacinus), 42, 70, 211, 212, 
214, 280, 295, 296. 

Tiger, 147, 149, 150. 

Tolypeutes, 280. 

Tragulina, 4, 35, 174, 270, 304, 32%. 

Trichecus (Walrus), 44, 316, 333- 

Troglodytes, 260; see also Gorilla and 
Chimpanzee. 

Tupaid, 50, 66, 151,263, 290; 230, 1303" 

Tylupoda, 4, 35, 174, 270, 321. 


U. 


UNGULATA, 3, 14; 19;, 335) 50, 62) 674 7s 
Ql, 162, 232, 250, 266, 291, 298, 302, 
304, 317- 

Ursid@, 91, 146, 231, 248, 314. 

Ursus (Bear), 49, 66, 144, 145, 248, 261, 
290, 301, 314. ; 


WV. 


Vesperugo, 33- 
ViscacHA (Lagostomus), 157, 160, 317- 
Viverra, 49. 


Viverrule, QI, 149, 248, 314. 


W. 


Watrus (T7r7ichecus), 49, 316, 333- 

Weasel (JZustela), 49, 147 

Whale (Balena), 37, 38. 79-81, 90, 195, 
196, 197, 198, 232, 271, 272, 294, 3045 


395- 
Wombat (Phascolomys), 42, 43, 59, 62, 
JO, 95) 216, 237, 242, 253, 280, 295, 324, 


Dan 


ACHUFUS, 279+ 


Ji 
Ziphius, 52, 94, 193. 


R. CLAY, SONS, AND TAYLOR, PRINTERS. 


Mee 


iii 


00738 0751