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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
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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.)
= :
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. )
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