SKELETON AND THE TEETH.








THE
PRINCIPAL FORMS
OF THE
SKE LETOETON
AND OF THE
T EET H
BY
PROFESSOR R. OWEN, F. R. S., &c.,
AUTHOR OF " ODONTOGRAPHY   " LECTURES ON COMPARATIVE ANATOMY;"' ARCHETYPE OF
THE SKELETON;" " ON THE NATURE OF LIMBS;" " EISTORY OF BRITISH
FOSSIL MAMMALIA?" ETC. ETC.
P I  I  A D E L P II I A:
BLANCHARD AND LEA.
1 8 5 4.




PI-IILA1)ELPHIA:
T. K. AND P. G. COILLINS, PRINTERS.




PREFACE.
THE' following work has just appeared in London as
a portion of a series entitled Orr's Circle of the Sciences.
Believing that a treatise of so much value was worthy of
an independent position and a permanent form, the publishers issue it separately. Written by the most distinguished osteologist of the age, as an introduction to his
favorite science, it cannot fail to possess great interest
and value to all students of Zoology, Comparative Anatomy, and Geology, of which departments of knowledge
Osteology may now be regarded as the foundation. As
indicative of the principles which have guided the author
in his labors, the following paragraphs are extracted from
the Preface to the Circle of the Sciences.
"In regard to the structure and conformation of that
great division of the Animal Kingdom called'the Vertebrate,' to which Man himself belongs, and which includes
the animals that most resemble Man, it has been deemed
sufficient for present purposes to restrict the Essay to the
fundamental structures or framework of the body, with
the appendages of a like enduring material called the
1*




vi                  PREFACE.
Teeth. The execution of this part of the'CIRcLE' has
been confided to that great philosophical anatomist who
has so distinguished himself in working out the true
principles of Osteology-principles which will doubtless
soon be applied to the nomenclature and description of
every branch of Anatomical Science. Avoiding the common practice of intrusting the special essays to literary
compilers and abridgers, it has been part of the design
of the work-hitherto with success-to engage, in the
important task of teaching, those master-spirits who have
in their day effected the greatest improvements, and made
the most decided advances, in their respective departments of science. The result has been, as is especially
shown in the Essay on the Principal Forms of the Skeleton,
an original exposition of the principles of Anatomical
Science, and of the most important results that have been
attained by its latest cultivator; such exposition being
succinct without any important omission, and as clear
and comprehensible as is consistent with the inevitable
use of technical terms.
"New and clearly defined ideas must be expressed by
their appropriate signs. The explanation of the sign
teaches the nature of the idea. Without learning and
understanding the technical terms of a science, that science cannot be comprehended. The terms seem'hard'
only while the ideas which they represent are not understood. We listen with pleasure and surprise to the glib
facility with which the working classes, admitted in




PREFACE.                   Vii
homely attire at half price to the Zoological Gardens on
Mondays, talk of the Elephant, the Rhinoceros, and the
Hippopotamus. These derivations from the Greek are
no harder to them than the Saxon monosyllabic names
of the bear, the seal, or the lion; and yet the four syllabled and five-syllabled names above cited are longer than
the average of the technical terms derived from the same
learned and pliable language: for example, Alisphenoid
is not really harder than rhinoceros, nor Neurapophysis
than hippopotamus; and when the mind becomes as
familiar with the things of which these are the verbal
signs, they fall naturally and easily into the circulating
medium for the currency of thought. To the intelligent
reader of every class, who may be blessed with the healthy
desire for the attainment of knowledge, let it then be
said: Be not dismayed with the array of'hard words'
which seems to bar your path in its acquisition. WVhere
such words are invented or adopted by the masters in
science, be assured that your acquisition and retention of
their meaning will be the safest'first steps' in the science
of your choice.
"Where plain and known words of Saxon or old English root could convey the meaning intended, the writers
have sedulously striven to use them instead of terms of
more exotic origin. But where the signification of a
thing, or group of things, would have demanded a roundabout explanation, or periphrase, as the alternative for
abandoning the single-worded and clearly defined tech



Viii                 PREFACE.
nical term, they have not hesitated to use such term,
appending, either in the same page or in the Glossarial
Index, its derivation and meaning.
"In reference to the terms of Anatomy, a method has
been adopted further to facilitate their reception and
easy recognition by reference to the part itself so signified in the wood-cuts; the same or corresponding part
bearing the same numerals in all the cuts; thus the scapula, or blade bone, is indicated by the No. 51 in the
fishes' skeleton, Fig. 9, and in all the succeeding skeletons up to those of the Ape and Man, Fig. 46."




CONTENTS.
ON THE PRINCIPAL FORMS OF THE SKELETON.
PAGE
Principles of Osteology... 13
Composition of Bones.                                          14
Primary Classification of Bones.                               16
The Dermoskeleton.17
Growth of Bones.21
Structure of Bones in Different Classes..  24
The Neuroskeleton.                                              26
The Vertebrm.27
Archetype of the Skeleton.                                    29
Skeleton of the Fish.35
The Sea-perch.38
The Occipital Vertebra.40
The Parietal Vertebra.                                         44
The Frontal Vertebra.                                          45
The Nasal Vertebra.47
Names of Bones.                                                49
Bones of the Head.50
Jaws of Fishes                                                  62
The Caudal Vertebra,.54
The Fin-rays.55
Adaptation of the Fish's Skull and Skeleton to Aquatic Life     67
Action of the Fins.........  63
Principal Forms of the Skeletons of Reptiles                    64
Batrachian Illustrations..                                66
Skeleton of the Frog.....                    68
Osteology of the Serpent Tribe...                   75
Skeleton of the Serpent...                       75
Structure of the Serpent's Skull....             76




X                     CONTENTS,
PAGE
Structure of the Skull of the Python..                79
The Maxillary Arch...                    81
Skull of the Boa-Constrictor...           81
The Mandibular Arch..                                 82
Skull of Poisonous Serpents....                      84
Vertebrae of the Rattlesnake....  85
Vertebrae of Serpents..                               86
Osteology of Lizards..                                91
Skeleton of the Crocodile...             95
Vertebrae and Skull of the Crocodile...         — 112
Limbs of the Crocodile..                            115
Osteology of Chelonian Reptiles...                  122
Carapace of the Turtle.                               ]124
Plastron of the Turtle..                            126
Vertebrse, Skull, and Limbs of the Tortoise and Turtle  129
The SIkeleton of Birds....                 134
Of the Swan...137
Of the Duck Tribe..                                  140
Pelvis and Leg of Birds.... 145
Structure of the Foot in Birds...                   147
Mechanism of Flight in Birds..                       150
Forms of the Skeleton in the Class Mammalia           151
Various Forms of Limbs in Mammals.                   153
Skeleton of the Whale.....   153
Of the Dugong......157
Of the Seal.....            158
Of the Walrus......                                 159
Skeletons of Hoofed Quadrupeds.                      162
Of the Horse......163
Of the Rhinoceros......    167
Of the Giraffe......                             170
Skeletons of Herbivorous Quadrupeds......  174
Of the Camel...                                    175
Of the Hippopotamus......      178
Osteological Characters of even-toed Hoofed Beasts...180
The Nature of Limbs.                                 183
The Protopterus.                                     ] 83
Law of Simplification of Feet..                      185
The Amphiuma and the Proteus..                       184
The Tarsal Bones of the Horse and the Ox..          185




CONTENTS.                              Xi
PAGE
The Tarsal Bones of the Rhinoceros, the Hippopotamus, and the
Elephant..........  187
Skeleton of the Sloth..... 188
Of the Ant-eater..... 193
Of the Mtole....194
Of the Bat....198
Skeletons of the Carnivorous Mammalia..                          200
Of the Lion....202
Of the Kangaroo.                                                  205
Conditions of Marsupial Structure...                 207
Skeletons of the Orang, and of Man....          210
Comparison of the Bony Structure of the Ape and Man.    211
Adaptation of the Human Skeleton to the erect Posture.  214
Modifications of the Human Skeleton, in relation to the Archetype  216
General and Special Terms in Osteology.221
The Facial Angle.222
Progressive Expansion of the Cranium.222
Crania of the Crocodile and the Albatross.222
Crania of the Dog and the Chimpanzee.223
Skulls of the Australian and the European.                       224
Concluding Remarks.225
ON THE PRINCIPAL FORAIS AND STRUCTURES OF
THE TEETH.
Intimate Relation of the Teeth to the Food and Habits of the Animal 229
Dental Tissues and Pulp Cavities.                                 231
Section of the Human Tooth.                                        232
Chemical and Structural Composition of Teeth                      234
Complex and Compound Teeth...                                  235
Section of.the Horse's Incisor....   2385
Transverse Section of Tooth of the Labyrinthodon                  236
Transverse Section of the Orycteropus..                         238
Grinders of an Elephant..... 239
Dental System of Fishes..... 240
Skull and Teeth of the Pike..                                  240
Jaws and Teeth of the Sting-ray..                           242
Teeth of the Wolf-fish......             245, 246
Tissue of Teeth in Fishes..... 247
Teeth of the Barracuda Fish....248




Xii                     CONTENTS.
PAGE
Dental System of Reptiles........    251
Teeth of the Iguanodon and the Megalosaurus               252
Skull and Teeth of the Dicynodon.....     254
Teeth of Crocodiles.....                               255
Teeth of Poisonous Snakes.                               256
The Dental System of Mammalia....           258
Form, Fixation, and Structure of Mammalian Teeth      25.. 9, 2561
Teeth of the Carnivora..                             264
Of the Lion.....                                          265
Of the Morse..... 266
Of the Porcupine..                                       267
Teeth of the Rodent Mammalia....                  69
Of the Horse......                         271
Of the Elephant..                                274
Of the Siberian Mammoth..... 275
Succession of the Elephant's Grinders..                 281
Development of the Elephant's Grinders..                 284
Teeth of the Megatherium..... 292
Of the extinct Anoplotherium.                 297
Of Ruminants....298
Of the Seal Tribe.........                      299
Of the Quadrumana..                                       301
Of the Orang and the Chimpanzee..                        301
Of Monkeys and Lemurs..... 307
Homologies of the Teeth..... 308
Deciduous and Permanent Teeth of the Hog                   310
Homologies of the Human Teeth..... 311
Notation and Symbols of Teeth.......                  813




LIST OF ILLUSTRATIONS.
FIG.                                                              PAGE
1. Dermo and Neuro Skeletons of the Sturgeon..                17
2. Portions of Dermo and Neuro Skeletons of the Armadillo            19
3. Typical Vertebra (Ideal)..                                      27
4. Parietal Segment, or Vertebra-Man..                             28
6. Thoracic Segment, or Vertebra-Raven..                            28
6. Typical Vertebra..                                               28
7. Archetype Vertebrate Skeleton....   29
8. Section of Vertebrae-Fish..                                     34
9. Skeleton of the Perch....                                      38
10. Sections of the Caudal Vertebra3 of Fishes...   54
11. Vertebrne of the Batrachians.......   65
12. Skeleton of the Frog........   70
13. Skeleton of the Cobra..... 74
14. Skull of Boa-Constrictor....S.  81
15. Skull of a Poisonous Snake..                                    84
16. Vertebra of the Rattlesnake.......   85
17. Section of Skull, Boa-Constrictor....         90
18. Skeleton, of the Crocodile.....         95
19. Atlas and Axis Vertebrua of the Crocodile....   96
20. Skeleton of the European Tortoise.....         123
21. Carapace of Turtle........ 124
22. Plastron of Turtle..                                           126
23. Segment of Carapace and Plastron.....       128
24. Skeleton of the Swan.....                                 137
25. Foreshortened View of the Skeleton of a Whale, showing its
Relative Size to Man.                                154
26. Skeleton of the Dugong..                              157
27. Skeleton of the Walrus.....   159
28. Skeleton of the Horse.....163
29. Skeleton of the Rhinoceros.....                           167
2




xiv               LIST OF ILLUSTRATIONS.
FIG.                                                              PAGE
30. Skeleton of the Giraffe.                                       1170
31. Skeleton of the HEippopotamus...... 178
32. Segment of the Skeleton of Protopterus.                  183
33. Segment of the Skeleton of Amphiuma..                          184
34. Segment of the Skeleton of Proteus..                          184
35. Tarsal Bones of the Horse..                                    185
36. Tarsal Bones of the Ox..... 185
37. Tarsal Bones of the Rhinoceros....          187
38. Tarsal Bones of the Hippopotamus..                            187
39. Tarsal Bones of the Elephant..... 187
40. Skeleton of the Sloth..... 190
41. Skeleton of the Mole.....       195
42. Skeleton of the Bat..... 199
43. Skeleton of the Lion..... 202
44. Skeleton of the Kangaroo..                                    205
45. Skeleton of Orang..                                          210
46. Skeleton of Man..                                              210
47. Facial Angle of Crocodile..                                 222
48. Facial Angle of Albatross..                                    222
49. Facial Angle of Dog..... 223
50. Facial Angle of Chimpanzee..                                   223
51. Facial Angle of Australian....... 224
52. Facial Angle of European.                                   224
53. Section of HIuman Incisor Tooth....    230
54. Structure of Human Tooth.....                             232
55. Section of Horse's Incisor..                                 235
56. Transverse Section of Tooth of Labyrinthodon.       236
57. Transverse Section of part of Tooth of Orycteropus              238
58. Longitudinal Section of part of Grinder of Elephant.    239
59. Skull of the Pike, showing the Teeth....     240
60. Jaws and Teeth of the Sting-Ray..                  242
61. Teeth of the Wolf-fish........ 246
62. Tooth of the Megalosaurus.....                            252
63. New-Formed and Worn Teeth of the Iguanodon.        252
64. Skull and Tusks of Dicynodon lacerticeps..             254
65. Tooth, with Germs of Successors, of the Garrhial.              255
66. Poison-Fang of Rattlesnake..                     257
67. Section of a Poison-Fang of Rattlesnake.                  257
68. Skull of a Rattlesnake.....    258
69. Jaws and Teeth of the Lion.....       263




LIST OF ILLUSTRATIONS.                        XV
FIG.                                                         PAGE
70. Skull and Teeth-of the Morse..                  266
71. Skull and Teeth of the Porcupine...... 267
72. Grinding Surfaces of the Upper and Lower Molars of Horse. 271
73. Section of Skull and Teeth of Elephant.    274
74. Molar Teeth of Elephant and Siberian Mammoth..    278
75. Deciduous and Permanent Teeth of the Hog...        310
76. Deciduous and Permanent Teeth, Human, set. 7..   312








THE
PRINCIPAL FORMS OF THE SKELETON.
PRINCIPLES OF OSTEOLOGY.
THE original substance of animals consists of a fluid
with granules and cells. In the course of development,
tubular tracts are formed, some of which become filled
with "neurine," or nervous matter; others with "myonine," or muscular matter; other portions are converted
into glandular substance; and a great proportion of the
rest of the primordial matter forms " cellular substance."
This substance, in many animals, becomes hardened, in
certain parts of the body, by earthy salts. When those
salts consist chiefly of phosphate of lime, the tissues called
"osteine," or bone, and " dentine," are constituted, between
which the chief distinction lies in the mode of arrangement of the earthy particles, in relation to the maintenance of a more or less free circulation of the nutrient
juices through such hardened or calcified tissues. In
bone, certain canals are left, of a caliber sufficient for the
passage of capillary bloodvessels through the tissue. Still
more minute tubes, sometimes expanding into cell-like
cavities, are established for the slower percolation of the
colorless fluid of the blood, called "plasma," or "liquor
sanguinis."  In true or hard dentine provision is made,
2




14             COMPOSITION  OF BONES.
by fine tubes, for the passage of plasma through its substance; but the red particles of the blood are excluded.
True osteine and dentine are peculiar to the highest
division or province of the Animal Kingdom, which province has been termed " Vertebrata," from the prevalent
disposition of the osseous matter in successive groups of
more or less confluent bones called "vertebrae."  (From
verto, I turn; these being the parts on which the body
bends or rotates.)
Before entering upon the disposition of the bony matter, a few words may be premised as to the composition
of that matter in the different classes of vertebrata. These
classes are four: Fishes, Reptiles, Birds, and Mammals,
which latter class includes the hair-clad beasts, commonly
called quadrupeds, with the naked whales and human
kind. Fishes have the smallest proportion, birds the
largest proportion, of the earthy matter in their bones.
The animal part in all is chiefly a gelatinous substance.
PROPORTIONS OF EARTHY OR INORGANIC, AND OF ANIMAL OR ORGANIC,
IATTER IN THE BONES OF THE VERTEBRATE ANIMALS.
FI SHES.
Salmon.        Carp.          Cod.
Organic... 60.62          40.40         34.30
Inorganic... 39.38          59.60         65.70
100.00        100.00         100.00
REPTILE S.
Frog.        Snake.         Lizard.
Organic... 35.50          31.04         46.67
Inorganic... 64.50          69.96         53.33
100.00        100.00        100.00
MAMMALS.
Porpoise.    Ox.    Lion.     Man.
Organic... 35.90     31.00    27.70    31.03
Inorganic... 64.10     69.00    72.30     68.97
100.00    100.00    100.00    100.00




PRTIMARY CLASSTFICATION  OF BONES.                 15
BIRD S.
Goose.       Turkey.        Hawk.
Organic..  32.91          30.49         26.72
Inorganic... 67.09         69.51         73.28
100.00        100.00        100.00
From the above table, it will be seen that the bones of
the fresh-water fishes have more animal matter, and are,
consequently, lighter than those of fishes from the denser
element of sea-water; and that the marine mammal called
porpoise differs little from the sea-fish in this respect.
The batrachian frog has more animal matter in its bones
than the ophidian or saurian reptiles, and thereby, as in
other respects, more resembles the fish. Serpents almost
equal birds in the great proportion of the osseous salts,
and hence the density and ivory-like whiteness of their
bones.
The chemical nature of the inorganic or hardening
particles, and of the organic basis of bone, is exemplified
in the subjoined table, including a species of each of the
four classes of vertebrata:CHEMICAL COMPOSITION OF BONES.
IIawk.   Man.  Tortoise.   Cod.
Phosphate of lime with trace
of fluate of lime..    64.39   59.63   52.66   57.29
Carbonate of lime....03    7.33   12.53    4.90
Phosphate of magnesia..    0.94    1.32    0.82    2.40
Sulphate, carbonate, and chlorate of soda                  0.92    0.69    0.90    1.10
Glutin and chondrin           25.73   29.70   31.75   32.31
Oil..0.99    1.33    1.34    2.00
100.00  100.00  100.00  100.00
Bony matter is very variously disposed in the bodies
of vertebrate animals. The sturgeon, the crocodile, and




16           COMPOSITION OF BONES.
the armadillo, are instances of its accumulation upon or
near the surface of the body; and hence the ball-proof
character of the skin of the largest of these mailed examples. The most constant position of bone is around the
central masses of the nervous and vascular systems, with
rays thence extending into the middle of the chief muscular masses, forming the bases of the limbs. Portions
of bone are also developed to protect and otherwise subserve the organs of the senses, and in some species are
found encasing mucus-ducts, and buried in the substance
of certain viscera; as, e. g., the heart in the bullock and
some other large quadrupeds. Strong membranes, called
"aponeurotic," and certain leaders or tendons, become
bony in some animals; as, e. g., the "tentorium" in the
cat, the temporal fascia in the turtle, the leaders of the
leg-muscles in the turkey, the nuchal ligament in the
mole, Fig. 41, u, and certain tendons of the abdominal
muscles of the kangaroo, which, so ossified, are called the
"marsupial bones," Fig. 44.
For a clear and intelligible view of the osseous system
in general, it has become requisite to make a primary
classification of its parts according to their prevalent
position, as in the cases above cited. The superficial or
skin-bones constitute the system of the "dermoskeleton"
(from the Greek dermna, skin, and skeleton); the deep-seated
bones, in relation to the nervous axis and locomotion,
form the "neuroskeleton" (Gr. neuron, nerve, and skeleton);
the bones connected with the sense-organs and viscera
form the "splanchnoskeleton (Gr. splagchnon, viscus, or
inward part, and skeleton); those developed in tendons,
ligaments, and aponeuroses, the "scleroskeleton" (Gr.
scleros, hard, and skeleton). These technical terms may
seem harsh, and sound strange, to those commencing the




THE DERMOSKELETON.                  17
study of the structure of animals, but the most complex
product of creation cannot be comprehended without
terms expressive of the results of the classification and
generalization of the manifold phenomena it offers to the
contemplative student.
In the arrangement of the parts of the dermo, splanchno,
and scleroskeleton, no common pattern is recognizable.
One can discern a definite end or purpose gained by the
positions those terms indicate of certain bony plates, cases,
or rods, and the special relation of such to the habits and
well-being of the creatures manifesting them; but the
diversity in the number, size, shape, and relative position
of such dermal bones and visceral bones seems interminable.
The head of the sturgeon, Fig. 1, is defended by a case
of superficial bony plates, d 3, d 7, d 11, &c.; and the body,
by five longitudinal rows of similar plates —one extendFig. 1.
di~ dl        I 3 \Q
57      I'    26'0
DERMO AND NEURO SKELETONS-STURGEON (Acipenser Sturio).
ing alone the mid-line of the back, ds, ds, one along each
side of the body, dp, dp, and two along the belly, cdh, dh,
between the fins called "pectoral," 57, and ventral. The
observations of the ichthyologist, or of those concerned
2*




18            THE DERMOSKELETON.
in the capture of the sturgeons for the sake of their airbladder, of wrhich the most valuable isinglass consists,
show us how well the external defensive armor of these
fishes is adapted to their mode of life. The sturgeons
may be called the scavengers of the great rivers which
they frequent. They habitually swim low, and grovel
along the bottom, turning up the mud and sand with their
pig-like snout, testing the disturbed matter with their
feelers, 6, and feeding in shoals, on the decomposing
animal and vegetable substances which are carried down
with the debris of the continents drained by those rapid
currents; thus, they are ever busied reconverting the
substances, which otherwise would tend to corrupt the
ocean, into their own living organized matter. These
fishes are, therefore, duly weighted by a ballast of dense
dermal, osseous plates-not scattered at random over
their surface, but regularly arranged, as every seaman
knows how ballast should be, in orderly series along the
middle and sides of the body. The protection against
the logs and stones hurried along their feeding-grounds,
which the sturgeons derive fiom their plate armor, renders needless the ossification of the immediate case of the
brain and spinal marrow, and, consequently, all the parts
of the neuroskeleton, ch, pI, n, ns, remain in the flexible,
elastic, gristly state; the weight of the dermoskeleton
requiring that the other systems of the skeleton should
be kept as light as might be compatible with its defensive
and sustaining functions. This view of the final purpose
of the dermal bony plates in the existing sturgeons affords
some insight into the habits and conditions of existence
of the similarly mailed extinct fishes which abounded in
the seas of the secondary periods of the geological history
of this planet. In most of these fishes, as in the stur



THE DERMOSKELETON.                    19
geons, the dermal bones are coated externally with a
much harder material, resembling enamel, and such fishes
have accordingly been termed "ganoid," from the Greek
word "' ganos," signifying brightness. The ganoid plates
in those extinct fishes are usually more close-set, overlapping each other, and being fastened together like tiles,
by a peg of one entering a socket in the next, and reciprocally. Only two genera of fishes are now known to
exhibit this beautiful arrangement of the dermal bones,
viz. the polyptertus of the Nile, and the lepidosteus of the
Ohio, and other great rivers of North America.
In the armadillo, the dermal bones, Fig. 2, oh, are small,
Fig. 2.
PORTIONS OF DERMO AND NEURO SKELETONS-ARMADILLO (Da8ypus8 tricilctusm).
polygonal, usually five or six-sided, smooth on their inner
surface, which rests on the soft subcutaneous layer of cellular tissue, variously sculptured on the outer and exposed side, but with a pattern constant in, and characteristic of, each species. They are united together at their
thick margins by rough or " sutural" surfaces, and resemble a tessellated pavement. The trunk is protected by a
large buckler of this bony armor; the head is defended




20            THE DERMIOSKELETON.
by a casque of the same; and the tail is encased in a sheath
of similar interlocked ossicles. To allow of the requisite
movements of the trunk in the small existing armadillos,
which, when attacked, roll themselves into a ball, from
three to nine transverse rows of the dermal bones, b b,
are interposed, having a yielding elastic junction with
each other, and with the anterior, o o, and posterior fixed,
and larger, parts of the trunk-armor; and by this modification the head and limbs can be withdrawn beneath the
armor, when its parts are pulled together by the strong
cutaneous muscles into a hemispheric form. In South
America, to which continent the armadillos are peculiar,
remains of gigantic quadrupeds, similarly defended, have
been discovered in the more recent tertiary deposits; but
in these colossal armadillos (Glyptodon) the trunk-armor
was in one immovable piece, covering the back and sides,
and was not divided by bands. Besides the defence which
such a modification of the integuments would afford
against the attacks of predatory animals, the armadillos
and glyptodens habitually frequenting the great forests
of South America may have been protected by the same
hard, arched covering from falling timber.
Such are some of the instances of the structure and
uses of the dermoskeleton in the vertebrate province.
The development of this system of the skeleton is not
dependent on the grade of organization, for we find it in
the highest and in the lowest classes; nor does a great
amount of osseous matter in the skin necessarily involve
a small amount or absence of the same matter in the
deeper-seated skeleton; for all the parts of this system of
bones, a, c, d, rn, ns, are as well developed and as well
ossified in the armadillos as in the quadrupeds which are
covered by hair. The different states of the neuroskele



GROWTHI  OF BONES.                21
ton, in the sturgeon and armadillo, are explicable only
with reference to the different media and other conditions
under which the two vertebrates were destined to exist.
In no species, and in no system of the skeleton, are
bones a primary formation of the animal: they are the
result of transmutations of pre-existing tissues, as substances composing animal bodies-e. g. nerve, muscle,
membrane, &c.-are called. The inorganic salts, defined
in the tabular view of the composition of bone, pre-exist
in the blood, in the albumen of the egg of the oviparous
vertebrates, and in the milk which nourishes the new-born
mammal.
The primitive basis, or "blastema," of bone is a subtransparent glairy matter, containing a multitude of
minute corpuscles. It progressively acquires increased
firmness-sometimes assumes a membranous or ligamentous state, sometimes a gristly state, before its conversion
into bone. Its assumption of the gristly state is attended
by the appearance in it of numerous minute nucleated
cells. As the gristle or " cartilage" hardens, these cells
increase in number and size, and are aggregated in rows at
the part where ossification is about to begin. These rows,
in the cartilaginous basis of long bones, are vertical to its
ends-in that of flat bones they are vertical to the peripheral edge. The nucleated cells are the instruments by
which the earthy particles are arranged in order; and in
bone, as in tooth, there may be discerned, in this predetermined arrangement, the same relation to the acquisition of strength and power of resistance, with the greatest
economy of the building material, as in the disposition of
the beams and columns of a work of human architecture.
Osteine, so formed, is arranged in thin plates, concen



22              GROWTH OF BONES.
trically around the vascular canals, around the entire circumference of the long bones, and in interrupted plates,
connecting together the walls of the vascular canals, so
as often to give rise to a reticular disposition of the bony
substance.
In fishes, the bones continue to grow throughout life;
and their periphery, whether in the flat bones of the head
which overlap each other, or the thicker bones that interlock, is cartilaginous or membranous, and the seat of progressive ossification. The long bones of most reptiles
retain a layer of ossifying cartilage beneath the terminal
articular cartilage; and growth continues at their extremities while life endures. Some of the long bones in
frogs, birds, and most of those in mammals, have their
ends distinct from the body or shaft of the growing bone,
these separately ossified ends being termed " epiphyses."
The seat of the active growth of the shaft is in a cartilaginous crust at the ends supporting the epiphyses; when
these coalesce with the shaft, growth in the direction of
the bones' aaxis comes to an end; but there is a slower
growth going on over the entire periphery of the bone,
which is covered by a membrane called the "periosteum."
In this membrane, the vascular system of a bone, except
the vessel supplying the marrow-cavity, undergoes the
amount of subdivision which reduces its capillaries to
dimensions suited for penetrating the pores leading to the
vascular canals.
Thus bone is a living and a vascular part, growing by
internal molecular addition and change, and having the
power of repairing fracture or other injury. The shells
and crusts of molluscous and crustaceous animals are unvascular; they grow by the addition of layers to their
circumference, may be cast off when too small for the




GROWTH OF BONES.                 23
growing body, and be reproduced of a more conformable
size. When fractured, the broken parts may be cemented
together by newly superadded shell-substance from without; but are not unitable by the action of the fractured
surfaces from within.
Extension of parts, however, is not the sole process
which takes place in the growth of bone; to adapt a bone
to its destined office, changes are wrought in it by the
removal of parts previously formed. In fishes, indeed,
we observe a simple unmodified increase. To whatever
extent the bone is ossified, that part remains, and, consequently, most of the bones of fishes are solid or spongy
in their interior, except where the ossification has been
restricted to the surface of the primary gristly mould.
The bones of the heavy and sluggish turtles and sloths,
of the seals, and of the whale-tribe, are solid. But in the
active land quadrupeds, the shaft of the long bones of the
limbs is hollow, the first-formed osseous substance being
absorbed as new bone is being deposited from without.
The strength and lightness of the limb-bones are thus
increased after the well-known principle of the hollow
column, which Galileo, by means of a straw picked up
from his prison floor, exemplified, in refutation of a charge
of Atheism brought against him by the Inquisition. The
bones of birds, especially those of powerful flight, are remarkable for their lightness. The osseous tissue itself is,
indeed, more compact than in other animals; but its quantity in any given bone is much less, the most admirable
economy being traceable throughout the skeleton of birds,
in the advantageous arrangement of the weighty material.
Thus, in the long bones, the cavities analogous to those
called "medullary" in beasts, are more capacious, and
their walls are much thinner. A large aperture called




24 STRUCTURE OF BONES IN DIFFERENT CLASSES.
the "pneumatic foramen," near one end of the bone, communicates with its interior, and an air-cell, or prolongation of the lung, is continued into and lines the cavity of
the bone, which is thus filled with rarefied air insteac of
marrow. The extremities of such air-bones present a
light open network, slender columns shooting across in
different directions from wall to wall, and these little
columns are likewise hollow.
The enormous beak of the hornbill, which seems at
first sight to constitute so grave an impediment to flight,
forms one enormous air-cell, with very thin bony walls;
and in this bird, in the swifts, and the humming-birds,
every bone of the skeleton, down to the last joints of the
toes, is permeated by hot air. The opposite extreme to
the above members of the feathered class is met with in
the terrestrial apteryx (wingless bird of New Zealand),
and in the aquatic penguin; in both of which, not any
bone of the skeleton receives air. Intermediate gradations in the extent to which the skeleton is permeated by
air occur in different birds, and in relative proportion to
their different kinds and power of flight.
In the mammalian class, the air-cells of bone are confined to the head, and are filled from the cavities of the
nose or ear, not from the lungs. Such cells are called
"frontal sinuses," "antrum," "sphenoidal" and "ethmoidal
sinuses" in man. The frontal sinuses extend backwards
over the top of the skull in the ruminant and some other
quadrupeds, and penetrate the cores of the horns in oxen,
sheep, and a few antelopes. The most remarkable development of air-cells in the mammalian class is presented
by the elephant; the intellectual physiognomy of this
huge quadruped being caused, as in the owl, not by the




THE NEUROSKELETON.                  25
actual capacity of the brain-case, but by the enormous
extent of the pneumatic cellular structure between the
outer and inner plates of the skull-walls.
In all these varied modifications of the osseous tissue,
the cavities therein, whether mere cancelli, or small medullary cavities as in the crocodile, or large medullary
cavities as in the ox, or pneumatic cavities and sinuses
as in the owl, are the result of secondary changes by
absorption, and not of the primitive constitution of the
bones. These are solid at their commencement in all
classes, and the vacuities are established by the removal
of osseous matter previously formed, whilst increase proceeds by fresh bone being added to the exterior surface.
The thinnest-walled and widest air-bone of the bird of
flight was first solid, next a marrow-bone, and finally
became the case of an air-cell. The solid bones of the
penguin, and the medullary femur of apteryx, exemplify
arrested stages of that course of development through
which the pneumatic wing-bone of the soaring eagle had
previously passed.
But these mechanical modifications do not exhaust all
the changes through which the parts of a skeleton, ultimately becoming bone, have passed; they have been previously of a fibrous or of a cartilaginous tissue, or both.
Entire skeletons, and parts of skeletons, of vertebrate
animals exhibit arrests of these early stages of development; and this quite irrespective of the grade of the
entire animal in the zoological scale. The capsule of the
eyeball, for example, in man, is a fibrous membrane; in
the turtle, it is gristle; in the tunny, and most other
fishes, it is bone. The skeletal framework of the little
lancelet-fish (Branchiostoma) does not go beyond the fibrous
3




26           SEGMENTAL COMPOSITION.
stage of tissue change.' In the sturgeon, skate, and shark,
it stops at the gristly stage, and hence these fishes are
called " cartilaginous."  In most fishes, and all air-breathing vertebrates, it proceeds to the bony stage, with the
subsequent modifications and developments above recited.
The main part of the skeleton-what may be termed the
skeleton proper —consists of the neuro-skeleton; and it
is in the construction of this system that the most interesting and beautiful evidences of unity of plan, as well as
of adaptation to end, have been discerned. The parts of
the neuroskeleton are arranged in a series of segments,
following and articulating with each other, in the direction of the axis of the body, from before backwards in
brutes, from above downwards in man.
Cach complete segment, called "vertebra," consists of
a series of osseous pieces, arranged according to one and
the same plan (Fig. 3), viz: so as to form a bony hoop, or
arch, above a central piece, for the protection of a segment of the nervous axis, and a bony hoop, or arch,
beneath the central piece, for the protection of a segment
of the vascular system. The upper hoop is called the
"'tneural arch," N. (Gr. neuron, nerve); the lower one, the
"hamal arch," II (Gr. haima, blood); their common centre
is termed the "centrum," c (Gr. kentron, centre).  The
neural arch is formed by a pair of bones, called "neurapophyses," n n (Gr. for nerve and apophysis, a projecting
part or process); and by a bone, sometimes cleft or bifid,
called the "neural spine," ns; it also sometimes includes a
pair of bones, called " diapophyses," d d (Gr. dia, across,
or transverse, and apophysis). The hkemal arch is formed
1 The doctrine or study of this kind of development-the development
of substance and texture, as contradistinguished from that of size and
shape-is now termed "Histology," from the Greek histos, net or tissue,
and logos, a doctrine or discourse.




TYPICAL SEGMENTS, ORl VERTEBRJE.           27
by a pair of bones called "pleurapophyses," pl (Gr.
pleuron, rib, and apophysis); by
a second pair, called "hmemapo-         Fig. 3.
physes," h (Gr. for blood, and
apophysis; and by a bone sometimes bifid, called the "hemal'~ 
spine," hs.  It also sometimes
includes parts, or bones, called
"parapophyses" (Gr. para, trans-    n
verse, and apophysis).  Bones,
moreover, are developed, which            y
diverge as rays, from one or more
parts of a vertebra.  
The parts of a vertebra which
are developed from independent
centres of ossification are called
"autogenous;" those parts that TYPICAL VERTEBRA.-(IDEAL.)
grow out from previously ossified
parts are called " exogenous;" the autogenous parts of a
vertebra are its elements," the exogenous parts its "processes."  No part, however, is absolutely autogenous
throughout the vertebrate series, and some that are exogenous in most are autogenous in a few instances. The
line cannot be strictly drawn; and, in classifying the parts
of a vertebra, as of other parts of animals, or of entire
animals, the systematist must be guided by general rules,
to which there will ever be some exceptions.
The elements, or autogenous parts, of a vertebra are
the centrum, c, the neurapophyses, n, the neural spine, ns,
the pleurapophyses, p, the hemapophyses, h, and the
hbumal spine, As. The exogenous parts are the diapophysis (Fig. 5), d, the parapophysis (ib.) p, the zygapophysis
(Fig. 6), z (Gr. zugos, junction, and apophysis), the ana



28      TYPICAL SEGMENTS, OR VERTEBRYE.
pophysis (Fig. 2), a (Gr. anria, backwards, and apophysis),
the metapophysis (ib.), m (Gr. meta, between, and apophysis), the hypapophysis (Fig. 5), y (Gr. hypo, below, and
apophysis), and the epapophysis (Fig. 4), e (Gr. epi, above,
and apophysis). Of the autogenous parts, the neural spine
is most commonly exogenous; of the exogenous parts, the
parapophyses, diapophyses, and hypapophyses are sometimes autogenous.
Vertebrae are subject to many and great modifications
-e. g., as to the number of the elements retained in their
composition, as to the form and proportion of the elements,
and even as to the relative position of the elements;
but the latter modification is never carried to such a
degree as to obscure the general pattern or type of the
segment.
Fig. 4.               Fig. 5.            Fig. 6.,$
Do~~~~~~~~~~~' Z
ns
PARIETAL SEGMENT, OR    THORACIC SEGMENT, OR  TYPICAL VERTEBRA.
VERITEBRA —MAN.       VERTEBRARAVEN.
Sometimes, as in the example (Fig. 4) of the third segment of the human skeleton, the neural arch, N, is much




29
expanded, the haemal
one, H, is contracted;
and, in the expanded    I 3
neural arch, the autogenous diapophyses, dd,
are wedged between the 
neurapophyses, n, and  
the  enormously  expanded neural spine,
ns.  More commonly,
as in the example from     *c
the raven's thorax (Fig. 
5), the haemal arch, H I,
is much expanded, the      B 
neural one, N, contract-    i,
ed; and in the expanded
haymal'arch, the para-   I   a
pophysis, p, here exogenous, is wedged between the centrum, C,.                       w
and the pleurapophysis,! A   G5 
pi.  Sometimes, again,   
as is exemplified in the
tail of the crocodile and.., -'":
of many other animals,
both neural and hkemal
arches are alike con-  
tracted; the pleurapo-  a,    ~.,,
physes, pl, being exeluded from the latter,
and standing out as continuations of the confluent diapophyses, d, and          1'
3*   a
I  "' Z




30       ARCHETYPE OF THE SKELETON.
parapophyses, p. Such vertebrae deviate but little from
the ideal type of the vertebra, under its less developed
condition, as in Fig. 6.  The segments are commonly
simplified and made smaller as they approach the end of
the vertebral column or axis, one element or process after
another is removed, until the vertebra is reduced to its
centrum, as in the subjoined diagram (Fig. 7) of the archetype vertebrate skeleton. In this scheme, which gives a
side view of the series of segments or vertebrae, the nature
of the principal modifications to which they are subject
are indicated, at the two extremes of the series.
As the four anterior divisions of the great trunk of the
nervous system are called, collectively, "'brain," so the
four corresponding segments of the osseous system are
called "skull."  The head, therefore, is not otherwise a
repetition of the trunk, than in so far as each segment of
the skull is a repetition or "homotype" of every other
segment of the body; each being subject to modifications
which may give it an individual character, without obliterating its typical features. So neither are the "arms"
and "legs" repeated in the head in any other sense than as
the cranial vertebrae may retain their "diverging appendages," 25, 37, 44, 53, a.  The fore-limbs are actually
such appendages, 53, of the occipital vertebra, 1, 3, 2, 51,
52, 59, which appendages undergo modifications closely
analogous to those of the appendages of the pelvic segment, or "hind limbs," 65.  And inasmuch as in one
class the pelvic appendages, with their supporting hbemal
arch, 63, hs, are detached from the rest of their segment,
and subject to changes of position (Fig. 9), 63, 69; so also
in other classes the appendages of the occipital segment
are liable to be detached, with their sustaining hoemal
arch, and to be transported to various distances from their




ARCHETYPE OF THE SKELETON.               31
proper centrum and neural arch, as in Fig. 21, Nos. 51,
53, 57.
The four anterior neurapophyses, 14, 10, 6, 2, give issue
to the nerves, the terminal modifications of which constitute the organs of special sense.
The first or foremost of these is the organ of smell, 19,
always situated immediately in advance of its proper segment, which becomes variously and extensively modified
to inclose and protect it.
The second is the organ of sight, 17, lodged in a cavity
or "orbit" between its own and the nasal segment, but
here indicated above that interspace.
The third is the organ of taste, the nerve of which
perforates the neurapophysis, 6, of its proper segment,
called " parietal vertebra," or passes by a notch between
this and the neurapophysis, 10, of the frontal vertebra,
to expand in the organ, which is always lodged below,
in the cavity called "mouth," and is supported by the
hbemal spine, 41, hs, of its own vertebra.
The fourth is the organ of hearing, 16, indicated above
the interspace between the neurapophysis of its own
(occipital) and that of the antecedent (parietal) vertebra,
in which it is always lodged; the surrounding vertebral
elements being modified to form the cavity for its reception, which is called " otocrane." The jaws are the modified hmemal arches of the first two segments.
The mouth opens at the interspace between these hoemal
arches; the position of the vent varies (in fishes), but
always opens behind the pelvic arch, S, 62, 63, p, when
this is ossified.
Outlines of the chief developments of the dermoskeleton
in different vertebrates, which are usually more or less
ossified, are added to the neuroskeletal archetype; as,




32         ARCHETYPE OF THE SKELETON.
e. g. the median horn supported by the nasal spine, 15, in
the rhinoceros; the pair of lateral horns developed from
the frontal spine, 11, in most ruminants; the median folds,
DI, DII, above the neural spines, one or more in number,
constituting the " dorsal" fin or fins in fishes and cetaceans,
and the dorsal hump or humps in the buffaloes and camels;
similar folds are sometimes developed at the end of the
tail, forming a "caudal" fin, C, and beneath the haemal
spines, constituting the " anal" fin or fins, A, of fishes.
The different elements of the primary segments are
distinguished by peculiar markings:The neurapophyses by diagonal lines, thus — ///
The diapophyses by vertical lines — 111
The parapophyses by horizontal lines -
The centrum by decussating horizontal and vertical lines -
The pleurapophyses by diagonal lines —  \
The appendages by dots-' 
The neural spines and hkemal spines are left blank.
In certain segments, the elements are also specified by
the initials of their names:ns is the neural spine.
n is the neurapophysis.
p1 is the pleui-apophysis.
c is the centrum.
h is the hemapophysis, also indicated by the Nos. 21, 29, 44,
52, 58, 68, 64.
hs is the hsemal spine.
a is the appendage.
The centrum is the most constant vertebral element as
to its existence, but not as to its ossification. There are
some living fishes-and formerly there were many, now




ARCHETYPE OF TIIE SKELETON.              33
extinct-in which, whilst the peripheral elements of the
vertebra become ossified, the central one remains unossified; and here a few words are requisite as to the development of vertebrae.
The central basis of the neuro-skeleton is laid down in
the embryo of every vertebrate animal, as a more or less
cylindrical fibrous sheath, filled with simple cells containing jelly.  This fibro-cellulo-gelatinous column is
called "notochord," Fig. 1, ch (Gr. notos, black; chorda,
cord; in Latin, "chorda dorsalis"). The centrums, or
"bodies of the vertebrae," as anthropotomists call them,
are developed in and from the notochord. The bases of
the other elements of the vertebra are laid down in fibrous
bands, diverging from the notochord, and giving the first
indication of the segmental character of the skeleton. At
this stage, the skeleton of the little fish called "lancelet"
(Amphioxus lanceolatus) is arrested. These fibrous bands
are next converted into cartilage, and the cartilage is in
definite pieces in each segment, recognizable as "neurapophyses" (Fig. 1), n; "pleurapophyses" (ib.), p1; "neural
spine" (ib), ns-the centrums still remaining in their
primitive state as the undivided notochord (ib), ch. At
this stage, the skeleton of the sturgeon is arrested. The
peripheral elements may be converted into bone, the central ones remaining as notochord, as in the protopterus,
the lepidosiren, and many fossil fishes. But, more commonly, the next stage is the subdivision of the notochord
into a series of separate centrums, corresponding with the
pairs of neurapophyses and pleurapophyses-ossification
of all the parts being more or less imperfect, as in the
sharks and rays, which have thence been called " cartilaginous fishes." When the parts of the vertebrae have
become more completely ossified, as in the fishes called




34         DEVELOPMENT OF VERTEBRiE.
"osseous," ossification is rarely so advanced as in the
higher vertebrata. In most of these
Fig. 8.     fishes, e. g., a deep cavity is left at each
end of the centrum (Fig. 8), cc, which
cavity continues to be occupied by the
C    liquefied gelatinous remains of the
primitive notochord; and the charac1'    ~    teristic of such element in a fish's
SECTION OF VERTEBRl  skeleton is, that it is "biconcave."  Of
-FISH.
the minor amount of the earthy matter in the ossified parts of the skeleton of fishes, mention
has been already made; and the consequent greater flexibility and elasticity of such bones may be readily tested
by whoever will bend one of the long spines in the skeleton of a cod or turbot, and contrast its flexibility with
that of the similarly-shaped long and slender bone (pubis,
or fibula, e. g.) which he may find in the Christmas turkey
that follows in the feast.
Two or more contiguous vertebra are frequently subjected to the same kind of modification, either by way of
excess or defect, and such groups of modified segments
have received special names; such, for example, as "skull"
(cranium), "neck" (cervix), "chest" (thorax), "pelvis," and
" tail" (cauda); and these terms are reciprocally applied,
when modified as adjectives, to the individual vertebrae
so grouped together, and which are called "cranial vertebrae," "cervical vertebrae," "dorsal" or "thoracic vertebrme," "sacral" or "pelvic vertebrae," and "caudal vertebroe."




SKELETON OF THE FISH.                35
SKELETON OF THE FISH.
In all fishes, the extent of ossification is less than in
the higher vertebrate classes. Only in the skull do we
find all the elements of the typical segment represented
by bone. In the trunk, e. g., the hbemapophyses and
hsemal spines never advance beyond the fibrous stage of
tissue development.
Four segments enter into the composition of the skull
of fishes, answering to the first four in the archetype (Fig.
7), and they combine to constitute the bony framework
of a head, larger in proportion to the trunk than in any
other class of animals. The skull (Fig. 9), 3, 52, br, forms
a cone, whose base is vertical, directed backwards, and
joined to the trunk without an intervening neck, and
whose sides are commonly three in number, one superior,
and two lateral and inferior. The cone is shorter or
longer, more or less compressed or squeezed from side to
side, more or less depressed or flattened from above downwards, with a sharper or blunter apex,lin different species
of fishes. The base of the skull is perforated by the hole,
called "foramen magnum," for the exit of the spinal marrow; the apex is more or less widely and deeply cleft
transversely by the aperture of the mouth; the eye-sockets
or "orbits," or, are lateral, large, and usually with a free
and wide intercommunication in the skeleton; the two
vertical fissures behind are called " gill-slits," or branchial
or opercular apertures, and there is a mechanism, like a
door, 34, 35, 36, for opening and closing them. The
mouth receives not only the food, but also the streams of
water for respiration (indicated by the arrow br), which
escape by the gill-slits. The head contains not only the




36           SKELETON OF THE FISH.
brain and organs of sense, but likewise the heart and
breathing organs. The inferior or "haemal" arches are
greatly developed accordingly, and their diverging appendages support membranes that can act upon the surrounding fluid, and are more or less employed in locomotion;
one pair of these appendages, P, 57, answers, in fact, to the
fore-limbs in higher animals, and their sustaining arch,
51, 52, in many fishes, also supports the homologues of
the hind-limbs, V, 69. Thus brain and sense-organs,jaws
and tongue, heart and gills, arms and legs, may all belong
to the head; and the disproportionate size of the skull, and
its firm attachment to the trunk, required by these functions, are precisely the conditions most favorable for facilitating the course of the fish through its native element.
It may well be conceived, then, that more bones enter
into the formation of the skull in fishes than in any other
animals; and the composition of this skull has been
rightly deemed the most difficult problem in comparative
anatomy.  "It is truly remarkable," writes the gifted
Oken, to whom we owe the first clue to its solution,
" what it costs to solve any one problem in philosophical
anatomy. Without knowing the what, the how, and the
why, one may stand, not for hours or days, but weeks,
before a fish's skull, and our contemplation will be little
more than a vacant stare at its complex stalactitic form."
To show what the bones are that enter into the composition of the skull of the fish; how, or according to what
law, they are there arranged; and why, or to what end,
they are modified, so as to deviate from that law or archetype, will next be our aim. These points, rightly understood, yield the key to the composition of the skull in all
vertebrata, and they cannot be omitted without detriment
to the main end of the most elementary essay on the




COMPOSITION OF THE SKULL OF THE FISH.  37
skeletons of animals. The comprehension of the description will be facilitated by reference to Figs. 7 and 9; and
still more if the reader have at hand the skull of any
large fish.
In the cod (Gadus morrhua)', e. g., it may be observed,
in the first place, that most of the bones are, more or less,
like large scales; have what, in anatomy, is called the
" squamous" character and mode of union, being flattened,
thinned off at the edge, and overlapping one another; and
one sees that, though the skull, as a whole, has less freedom of movement on the trunk, more of the component
bones enjoy independent movements. Before we proceed
to pull apart the bones, it may be well to remark that the
principal cavities, formed by their coadaptation, are the
"cranium," lodging the brain and the organs of hearing;
the "orbital," Fig. 9, or, and the "nasal," nl, chambers; the
buccal and branchial canals, br. Some of these cavities
are not well defined. The exterior of the skull is traversed by five longitudinal crests, intercepting four channels which lodge the beginnings of the great muscles of
the upper half of the trunk. The median crest is developed to an extreme height in some fishes, as, e. g., the
dolphin and light-horseman fish (Ephi ppus). The flatfishes (turbot, sole, &c.) are remarkable for the unsymmetrical character of the skull, in consequence of both
eyes being placed on one side of the head.
In the analysis of the cod's skull it is best to begin at
the back part; for the segments of the skeleton deviate
most from the archetype as they recede in position towards the two extremes of the body. After a little practice, one succeeds in detaching the bones which form the' The skull of this fish, conveniently prepared for this examination,
may be had of Mr. Flower, No. 22 Lambeth Terrace, Lambeth Road.
4




38          SKELETON OF THE PERCH.
I —
74                   km




OCCIPITAL SEGMENT, OR VERTEBRA.              39
back part or base of the conical skull, and which immediately precede and join those of the trunk; we thus obtain
a " segment" or "' vertebra" of the skull. If we next proceed to separate a little the bones composing this segment,
we find those that were most closely interlocked to be in
number and arrangement as follows: Two single and
symmetrical bones, and two pairs of unsymmetrical bones,
forming a circle; or, if the lower symmetrical bone, which
is the largest, be regarded as the base, the other five form
an arch supported by it, of which the upper symmetrical
bone is the keystone.'  This answers to the "neural"
arch of the typical vertebra: the base-bone is the "centrum," c; the pair of bones, which articulated with its
upper surface and protected the hind division of the brain,
form the "neurapophyses," n; the smaller pair of bones,
projecting outwards, like transverse processes, are the
"diapophyses," d; the symmetrical bone completing the
arch, and terminating above in a long crest or spine, is
the "neural spine," ns. It will be observed that the centrum is concave at that surface which articulates with the
centrum of the first vertebra of the trunk; the opposite
surface is also concave, but expanded and very irregular,
in order to effect a much firmer union with the centrum
of the next cranial segment in advance-great strength
and fixity being required in this part of the skeleton,
instead of the mobility and elasticity which is needed in
the vertebral column of the trunk. It may be also observed that the " neurapophyses" are perforated, like most
of those in the trunk, for the passage of nerves; that the
diapophyses give attachment to the bones which form the
great inferior or haemal arch; and that the neural spine
1 See my work "On the Archetype of the Skeleton," 8vo. 1848, p. 10,
Fig. 1.




40     OCCIPITAL SEGMENT, OR VERTEBRA.
retains much of the shape of the parts so called in the
trunk. Nevertheless, the elements of the neural arch of
this hindmost segment of the skull have undergone so
much development and modification of shape, that they
have received special names, and have been enumerated
as so many distinct and particular bones. The centrum,
No. 1, is called "basioccipital;" the neurapophyses, No.
2, "exoccipitals;" the neural spine, No. 3, " superoccipital;" the diapophyses, No. 4, "paroccipitals."  In the
human skeleton all those parts are blended together into
a mass, which is called the "occipital bone."
The entire segment, here disarticulated, in the cod-fish,
is called the " occipital vertebra," and in it we have next
to notice the widely expanded inferior or hbemal arch.
This consists of three pairs of bones. The first pair are
bifurcate, and have two points of attachment to the neural
arch, the lower prong, answering to what is called the
"head of the rib," abutting upon the neurapophysis; the
upper prong, answering to the "tubercle of the rib,"
articulating to the diapophysis. The second pair of bones
are long and slender, and represent the body of the rib.
The first and second piece together answer to the element
called " pleurapophysis; the third pair of bones are the
"hsemapophyses;" these support diverging appendages
consisting of many bones and rays. The special names
of the above elements of the hsemal arch of the occipital
vertebra are, from  above downwards, "suprascapula,"
No. 50; " scapula," No. 51; "coracoid," No. 52. The inverted arch, so formed, encompasses, supports, and protects the heart or centre of the hkemal system; it is called
the "scapular arch." There are animals-the gymnothorax and slow-worm, e. g.-in which this arch supports no
appendage; there are fishes-the protopterns, e. g. Fig. 32



OCCIPITAL SEGMENT, OR VERTEBRA.    41
in which it supports an appendage in the form of a single
many-jointed ray, retaining the archetypal character, Fig.
7, No. 53. In other fishes, the number of rays progressively increase, until, in those called "rays" par excellence,
they exceed a hundred in number, and are of great
length, forming the chief and most conspicuous parts of
the fish. The more common condition of the appendage
in question is that exhibited in the species figured, Cut 9.
So developed, it is called in ichthyology the "pectoral
fin:" otherwise and variously modified in higher animals,
the same part becomes a fore-leg, a wing, an arm, and
hand. Some of the special names, originally applied to
the parts of the scapular appendage in man, are retained
and applied to like parts in the pectoral fin of the fish.
Of the two flat bones connecting the fin with the coracoid,
the upper one is the " ulna," No. 54; the lower one the
"radius," No. 55; the row of short bones joined with
these are the "carpals," No. 56; the longer and more
slender many-jointed rays answer to the "parts called
"metacarpals" and " phalanges" in the human hand. In
the salmon there is a bone answering to the arm-bone or
humerus, which is articulated to the middle of the back
part of the coracoid by a transversely elongated extremity. It is also expanded at the distal end, where it
articulates by cartilage with the ulna and radius. The
ulna is a semicircular plate of bone perforated in the
centre, and, besides its articulation with the humerus, the
radius, and the ulnar carpals and metacarpal ray, it also
directly joins the broad coracoid. The radius, after expanding to unite with the humerus, the ulna, and the
radial carpals, sends a long and broad process downwards
and inwards, which is united by ligament with its fellow
and with the lower termination of the coracoid. A basis
4*




42     PARIETAL SEGMENT, OR VERTEBRA.
of adequate extent and firmness is thus insured for the
support of the pectoral fins. The carpal bones of these
fins are four in number, progressively increasing in length
from the ulnar to the radial side of the wrist. The metacarpo-phalangial rays are thirteen in number; the uppermost or ulnar one being the strongest, and articulating
directly with the ulna.
Proceeding to the next segment, in advance, in the codfish's skull, we find that the bone which articulated with
the centrum of the occipital segment is continued forward
beneath a great proportion of the skull. In quadrupeds,
however, the corresponding part of the base of the skull
is occupied by two bones; and if the single long bone in
the fish be sawn across at the part where the natural
suture exists in the beast, we have then little difficulty in
disarticulating and bringing away with it a series of bones
similar in number and arrangement to those of the occipital segment.
In the skeletons of most animals the centrums of two
or more segments become, in certain parts of the body,
confluent, or they may be connate; they form, in fact, one
bone, like that, e. g., which human anatomists call "sacrurn."  By the term "confluent" is meant the cohesion
or blending together of two bones which were originally
separate; by " connate," that the ossification of the common fibrous or cartilaginous bases of two bones proceeds
from one point or centre, and so converts such bases into
one bone: this is the case, e. g., in the radius and ulna of
the frog, and in its tibia and fibula. In both instances
they are to the eye a single bone; but the mind, transcending the senses, recognizes such single bone as being
essentially two. In like manner, it recognizes the "occipital bone" of man as essentially four bones; but these




PARIETAL SEGMENT, OR VERTEBRA.            43
have become "confluent," and were not "connate."  The
centrums of the two middle segments of the fish's skull
are connate, and the little violence above recommended is
requisite to detach the penultimate segment of the skull.
When detached, the bones of it are seen to be so arranged
as to form a neural and a heemal arch. In the neural arch
the centrum, neurapophyses, diapophyses, and neural spine
are distinct: moreover, the neural spine in the cod, and
many other fishes, is bifid, or split at the median line.'
The centrum is called "basisphenoid," No. 5; the neurapophysis, "alisphenoid," No. 6; the neural spine, "parietal," No. 7; and the diapophysis, "mastoid," No. 8.
The alisphenoids protect- the sides of the optic lobes, and
the rest of the penultimate segment of the brain; the
mastoids project outwards and backwards as strong transverse processes, and give attachment to the piers of the
great inverted hremal arch. Before noticing the structure
of this, I may remark that, in the recent cod-fish, the case,
partly gristly, partly bony, which contains the organ of
hearing, is wedged in between the last and penultimate
neural arches of the skull. The extent to which the earcase is ossified varies in different fishes, but the bone is
always developed in the outer wall of the case. In the
cod-fish it is unusually large, and is called "petrosal,"
No. 16; it forms no part of the segmented neuroskeleton.
In the organ which it contributes to inclose, there is a
body as hard as shell, like half a split almond; it is the
"otosteal," No. 16, or proper ear-bone.
The hemal arch consists of a pleurapophysis and a
hbemapophysis on each side, and a haemal spine; but all
these elements are subdivided; the pleurapophysis into
two parts, the upper one called "epitympanic," 28, a
"Archetype Vert. Skel.," p. 11, Fig. 2.




44     VARIETAL SEGMENT, OR VERTEBRA.
(common to this and the next arch in advance); the lower
one " stylohyal," No. 38. The hsemapophysis is a broader,
slightly arched bone; the upper division is called "epihyal," No. 39; the lower division, "ceratohyal," No. 40.
The henmal spine is subdivided into four stumpy bones,
called collectively "basihyal," No. 41; and which, in most
fishes, support a bone directed forwards, entering the substance of the tongue, called "glossohyal," No. 42; and
another bone directed backwards, called "urohyal," No. 43.
The ceratohyal part of the heemnapophysis supports, in
the cod, seven long and slender bent bones, called " branchiostegal rays," 44. The number of these rays differs
greatly in different fishes; the protopterus has but one
ray, the blenny has two rays, the carp three rays-a very
common number is seven; but the clops has thirty branchiostegal rays. They are of great length in the anglerfish (lophius), in which they serve to support a membrane,
developed to form a large receptacle on each side of the
head of this singular fish. Into these receptacles the
small fishes are transferred, which the angler attracts
within reach of its mouth, by the movable rod, line, and
bait attached to the top of its enormous head. In ordinary fishes, the branchiostegal rays support a membrane
which helps to close the gill-slit, and by its movements
contributes to the direction of the branchial currents. It
is an appendage, or rudimental limb, answering to the
pectoral'fin diverging from the hbemal arch, in the adjoining occipital segment.
The penultimate segment of the skull above described
is called the "parietal vertebra;" and the hbernal arch is
called the "hyoidean arch," in reference to its supporting
and subserving the movements of the tongue.
The next segment, or the second of the skull, counting




FRONTAL SEGMENT, OR VERTEBRA.            45
backward, can be detached from the foremost segment
without dividing any bone. It is then seen to consist,
like the third and fourth segments, of two arches and a
common centre; but the constituent bones have been
subject to more extreme modifications. The centrum,
called "presphenoid," No. 9, is produced far forwards,
slightly expanding; the neurapophyses, called "orbitosphenoids," No. 10, are small semioval plates, protecting
the sides of the cerebrum; the neural spine, or key-bone
of the arch, called "frontal," No. 11, is enormously expanded, but in the cod and most fishes is single; the
diapophyses, called "post-frontals," No. 12, project outwards from the hinder angles of the frontal, and give
attachment to the piers of the inverted hemal arch. The
first bone of this arch is common in fishes to it and to
that of the last-described vertebra, being the bone called
"epitympanic," No. 28 (Fig. 9); this modification is called
for by the necessity of consentaneous movements of the
two inverted arches, in connection with the deglutition
and course of the streams of water required for the branchial respiration. The hsemal arch of the present segment-enormously developed-is plainly divided primarily on each side into a pleurapophysis and hoemapophysis;
for these elements are joined together by a movable
articulation, whilst the bones into which they are subdivided are suturally interlocked together. The pleurapophysis is so subdivided into four pieces; the upper
one, articulating with the post-frontal and mastoid-the
diapophyses of the two middle segments of the skull-is
called "epitympanic," No. 28, a; the hindmost of the two
middle pieces is the "mesotympanic," No. 28, b; the foremost of the two middle pieces is the "pretympanic," No.
28, c; the lower piece is the hypotympanic, No. 28, d;




46      FRONTAL SEGMENT, OR VERTEBRA.
this presents a joint-surface, convex in one way, concave
in the other, called a "ginglymoid condyle," for the hsemapophysis, or lower division of the arch. In most airbreathing vertebrates —the serpent, Cut 16, e. g.-the
pleurapophysis resumes its normal simplicity, and is a
single bone, 28, which is called the "tympanic;" in the
eel-tribe it is in two pieces. The greater subdivision, in
more actively breathing fishes, of the tympanic pedicle,
gives it additional elasticity, and, by their overlapping,
interlocking junction, greater resistance against fracture;
and these qualities seem to have been required in consequence of the presence of a complex and largely-developed diverging appendage, which forms the framework
of the principal flap or door, called "operculum," that
opens and closes the branchial fissure on each side. The
appendage in question consists of four bones; the one
articulated to the tympanic pedicle is called "preopercular,"
No. 34; the other three are, counting downwards, the
"opercular," No. 35; the "subopercular," No. 36; the
"interopercular," No. 37. The hsemapophysis is subdivided into two, three, or more pieces, in different fishes,
suturally interlocked together; the most common division
is into two subequal parts, one presenting the concavoconvex joint to the pleurapophysis, and called "articular,"
No. 29; the other, bifurcated behind to receive the point
of 29, and joining its fellow at the opposite end to complete the ha3mal arch. It is very singularly modified by
supporting, and having more or less firmly attached to
it, a number of the hard bodies called " teeth," and hence
it has been termed the "dentary," No. 33. In the cod
there is a small separate bone, below the joint of the
articular, forming an angle there, and called the "angular
piece," No. 31.




NASAL SEGMENT, OR VERTEBRA.              47
In consequence of this extreme modification, in relation to the offices of seizing and acting upon the food,
the pair of hoemapophyses of the present segment of the
skull have received the name of "lower jaw," or "mandible" (mandibula). The entire segment is called the
"frontal vertebra."
The first segment, forming the anterior extremity of
the neuroskeleton, like most peripheral parts, is that
which has undergone the most extreme modifications.
The obvious arrangement, nevertheless, of its constituent
bones, when viewed from  behind, after its detachment
from the second segment, affords one of the most conclusive proofs of the principle of adherence to common type
which governs all the segments of the neuroskeleton,
whatever offices they may be modified to fulfil. The
neural arch plainly exists, but is now reduced to its essential elements —viz: the centrum, the neurapophyses, and
the neural spine. The centrum is expanded anteriorly,
where it usually supports some teeth on its under surface
in fishes; it is called the "vomer," No. 13. The neurapophyses are notched (in the cod) or perforated (in the
sword-fish), by the crura or prolongations of the brain,
which expand into its anterior divisions, called "olfactory
lobes;" the special name of such neurapophysis is " prefrontal," No. 14. The neural spine is usually single,
sometimes cleft along the middle; it is the " nasal," No. 15.
The hbemal airch is drawn forwards, so that its apex,
as well as its piers, are joined to the centrum (vomer) and
usually also to the neural spine (nasal), closing up anteriorly the neural canal. The pleurapophyses are simple,
short, sending backwards an expanded plate; they are
called " palatines," No. 20. The haemapophyses are simple, and their essential part, intervening between the




48 GENERAL AND SPECIAL NAMES OF BONES.
pleurapophysis and haumal spine, is short and thick; but
they send a long process backwards. This element. is
called "maxillary," No. 21. The hoemal spine, cleft at
the middle line, sends one process upwards, of varying
length in different fishes, and a second downwards and
backwards; and its under surface is beset with teeth in
most fishes; it is called "premaxillary," No. 22. Each
pleurapophysis supports a "diverging appendage," consisting commonly of two bones: the outer one, which fixes
the present haemal arch to the succeeding one, is called
"pterygoid," No. 24; the inner one is the "entopterygoid,"
No. 23. The entire segment is called the "nasal vertebra." The hnemal arch and its appendage form what is
termed the upper jaw (maxilla); the palatine and pterygoids forming the roof of the mouth, the maxillary and
premaxillary the proper upper jaw. On reviewing the
arrangement of the bones of the foregoing segments, one
cannot but be struck by the strength of the arches which
protect and encompass the brain, and by the beauty and
efficiency of that arrangement which provides such an
arch for each primary division of the brain; and a sentiment of admiration naturally arises on examining the
firm interlocking of the extended sutural surfaces, and
especially of those uniting the proper elements of the
arch with the buttresses wedged in between the piers and
keystone, and to which buttresses (diapophyses) the
larger hmamal arches are suspended.
In addition to the parts of the neuroskeleton, the bones
of the head include the ossified part of the ear-capsule,
"petrosal," 16, already mentioned; an ossified part of the
eye-capsule, commonly in two pieces, "sclerotals, No. 17;
and an ossified part of the capsule of the organ of smell,
"turbinal," No. 19. Another assemblage of splanchno



GENERAL AND SPECIAL NAMES OF BONES. 49
skeletal bones support the gills, and are in the form of
slender bony hoops, called " branchial arches." They are
articulated to and supported by the hyoidean arch.
Amongst the bones of the muco-dermal system, may be
noticed those that circumscribe the lower part of the orbit,
of which the anterior is pretty constant in the vertebrate
series, and is called "lachrymal," marked 20 in Cut 9.
In fishes, they are called " suborbitals," and are occasionally present in great numbers, as e. g., in the tunny. A
similar series of bones sometimes overarches the temporal
fossee, and are called "supertemporals."
At the outset of the study of Osteology, it is essential to
know well the numerous bones in the head of a fish, and
to fix in the memory their arrangement and names. The
latter, as we have seen, are of two kinds, as regards the
bones of the neuroskeleton; the one kind is "general,"
indicative of the relation of the skull-bones to the typical
segment, and which names they bear in common with the
same elements in the segments of the trunk; the other
kind is "special," and bestowed on account of the particular
development and shape of such elements, as they are modified in the head for particular functions. I would advise
any one earnestly desirous of comprehending this beautiful department of Comparative Anatomy, to obtain a
prepared and partially disarticulated skull of a cod-fish
from Mr. Flower,' in which every bone bears the initials
of its " general" name, and the numerals indicative of its
"special" name. A great proportion of the bones in the
head of a fish exist in a very similar state of connection
and arrangement in the heads of other vertebrata, up to
and including man himself. No method could be less
I Ante, p. 37.
5




50 CLASSIFICATION OF BONES OF THE HEAD.
conducive to a true and philosophical comprehension of
the vertebrate skeleton than the beginning its study in
man-the most modified of all vertebrate forms, and that
which recedes furthest from the common pattern.
Through an inevitable ignorance of that pattern, the
bones in anthropotomy are indicated only by special
names more or less relating to the particular forms these
bones happen to bear in man; such names, when applied
to the tallying bones in lower animals, losing that significance, and becoming arbitrary signs. Owing to the
frequent modification by confluence of the human bones,
collections of them, so united, have received a single
name, as e. g., "occipital," " temporal," &c.; whilst their
constituents, which are usually distinct vertebral elements,
have received no names, or are defined as processes, e. g.,
" condyloid process of the occipital bone," " styloid process
of the temporal bone," " petrous portion of the temporal
bone," &c. The classification, moreover, of the bones of
the head in Human Anatomy, viz: into those of the cranium and those of the face, is artificial or special, and
consequently defective. Many bones which essentially
belong to the skull are wholly omitted ini such classification.
In regard to the archetype of the vertebrate skeleton,
fishes, which were the first forms of vertebrate life introduced into this planet, deviate the least therefrom; and
according to the foregoing analysis of the bones of the
head, it follows that such bones are primarily divisible
into those ofThe Neuroskeleton;
The Splanchnoskeleton;
The Dermoskeleton.
The neuroskeletal bones are arranged in four segments,
called




CLASSIFICATION OF BONES OF THE HEAD. 51
The Occipital segment;
The Parietal segment;
The Frontal segment;
The Nasal segment.
Each segment consists of a " neural" and a " haemal" arch.
The neural arches areN   I. Epencephalic arch (bones Nos. 1, 2, 3, 4):
N II. Mesencephalic arch (5, 6, 7, 8);
N IIi. Prosencephalic arch (9, 10, 11, 12);
N Iv. Rhinencephalic arch (13, 14, 15).
The hoemal arches areH I. Scapular arch (50-52);
H II. Hyoidean arch (38-43);
H III. Mandibular arch (28-32);
H  Iv. Maxillary arch (20-22).
The diverging appendages of the hbemal arches are1. The Pectoral (54-57);
2. The Branchiostegal (44);
3. The Opercular (34-37);
4. The Pterygoid (23-24).
The bones or parts of the splanchnoskeleton which
are intercalated with or attached to the arches of the true
vertebral segments, areThe Petrosal (16) or ear-capsule, with the otolites, 16/";
The Sclerotal (17) or eye-capsule;
The Turbinal (19) or nose-capsule;
The Branchial arches;
The Teeth.
The bones of the dermoskeleton areThe Supratemporals;
The Superorbitals;
The Suborbitals;
The Labials.
Such appears to be the natural classification of the
parts which constitute the complex skull of osseous fishes.




52  MODIFICATIONS OF THE JAWS OF FTSHES.
The term " cranium" might well be applied to the four
neural arches collectively, but would exclude some bones
called "cranial," and include some called "facial," in Human Anatomy. In a side view of the naturally-connected
bones of the head of a fish, such as is shown in the figure
of the skeleton of the sea-perch, Cut 9, the upper part of
the head is formed by the neural spines called superoccipital, 3, frontal, 11, and nasal, 15; produced at the hinder
half into the median ridge. The right lateral ridge is
formed by the parietal, 7, and paroccipital, 4; the external
ridge by the post-frontal, 12, and the mastoid, 8. The
anterior termination of the series of centrums may be
partly seen through the widely-open orbits at 9 and 13,
indicating the presphenoid and vomer respectively. The
most conspicuous parts of the upper jaw are the premaxillary, 22, and the maxillary, 21, the latter being
edentulous, as in most fishes; the salmon and trout are
examples where No. 21 bears teeth.  The shape and
slight attachment of those bones relate to the necessity of
a movable mouth that can be protruded and retracted, in
a class of animals that derive no aid in the prehension of
their food from their limbs, which are reduced to fins.
The upper bent back part of the premaxillary is called
its "nasal branch," and is of unusual length in fishes with
protractile snouts, as, e. g., the dories (Zeus), certain wrasses
(Coricus), and especially the sly-bream (Sparus insidiator
of Pallas). In this fish, the nasal branch of the premnaxillary plays in a groove on the upper surface of the skull,
and reaches as far back as the occiput, when the mouth
is shut and retracted. The descending branch of the
premaxillary is attached by a ligament to the maxillary,
and, as this is similarly attached to the mandible, both
are protruded, when the long nasal branch of the pre



MODIFICATIONS OF THE JAWS OF FISHES. 53
maxillary is drawn forwards out of its epicranial groove.
This action is aided by the hypotympanic, which is of
great length, and has a movable articulation at both ends;
the lower end joining the mandible is pulled forward,
simultaneously with the protrusion of the premaxillary,
and co-operates therewith in the sudden projection of the
mouth, by which the sly-bream seizes, or shoots with a
suddenly-propelled drop of water, the small agile aquatic
insects that constitute its prey.
An opposite extreme of modification of the maxillary
and premaxillary bones, where unusual fixity and strength
are needed, is that presented by the "sword-fishes," in
which the premaxillaries constitute, by an unusual prolongation and density of tissue, the sword-shaped weapon
characteristic of the genera Xiphias and Istiophorus.
In Cut 9 the divisions 28 a, c, and d, of the tympanic
pedicle, and the two chief divisions, 29 and 33, of the
mandible, are shown, together with the four bones of the
opercular appendage; the preopercular, 34, being serrated
and spined, as in most perches.
Of the hyoidean arch may be seen the glossohyal, 42,
the ceratohyal, 40, with its branchiostegal rays, 44, and
the urohyal, 43. Of the scapular arch, the scapula, 51,
and the coracoid, 52, this supports not only the bones of
the "pectoral fin," P, viz: ulna, radius, with the small
carpal bones intervening between them and the metacarpophalanges, 57, but also the lower elements of the pelvic
arch, 63, and their diverging appendage, 69, called the
" ventral fin," V.
In the segments of the trunk the hbemapophyses, save
in the first vertebra, 58, and the pelvic vertebra, 63, are
not ossified; but they are represented by aponeurotic
fascia continued downwards from the ossified elements of
5*




54 MODIFICATIONS OF THE CAUDAL VERTEBRAE.
Fig. 10.           the segments; these elements
consist of the centrum, the neurapophyses, and neural spines,
the pleurapophyses, and the
parapophyses. In most fishes
the neural spines are connate,ail          with the neurapophyses, and
these become confluent with
the centrums in most of the
segments; the neurapophyses
are perforated directly by the
spinal nerves in many fishes,
as at nn (Fig. 8); they usually
Ipng   develop anterior zygapophyses,
Z (Fig. 9). The centrums are'biconcave in all fishes, save the
lepidosteus, in which they are
ill \\        convex in front, and concave
AS,          behind. The pleurapophyses,
opl (Fig. 9), form what are called
JV  "' false ribs," or free or "floating
h' s         ribs," in Anthropotomrny; they
articulate with the centrums in
the anterior trunk-vertebrae,
and then with the parapophyses, op, which are usually confluent with the centrum. The
parapophyses elongate, bend
v    down, and unite together at or
near to the end of the abdomen, and so form the contracted haemal canal, for the caudal
khs 4l          vessels, in the long and mus



STRUCTURE AND FORMULAF OF FIN-RAYS.  55
cular tail of the fish. The trunk-vertebra of a fish are
divisible into those which have free pleurapophyses, called
"abdominal vertebrae," and those without, and which
terminate below by narrow haernal arches and long
spines, called " caudal vertebrae." These haemal arches
are formed by different parts in different fishes; commonly by the bent-down and terminally confluent parapophyses (Fig. 10), I, p, cod; sometimes, as in the tunny
(ib.) III, by parapophyses, p, lengthened out by pleurapophyses, pi; sometimes, as in lepidosteus (ib.), II, by pleurapophyses, pl; but never, as in air-breathing vertebrates
(ib.), V, by ossified haeenapophyses, h, hs. These elements,
in the first vertebra of the trunk of a fish, are indeed
ossified, and form the long and slender bone called "'clavicle," 58 (Fig. 9), usually attached to the inner side of the
scapular arch. The hbemapophyses of, probably, the last
abdominal vertebra, called " ischia," No. 63, are detached
from the rest of their segment, and are either loosely
suspended in the flesh, beneath or near it, as in the fishes
called "abdominal;" or they are advanced, much elongated, and attached to the scapular arch, as in the fishes
called "thoracic" (Fig. 9); or they are more advanced,
shortened, and similarly attached, as in the fishes called
"jugular;" or they are wholly wanting, as in the fishes
called " apodal."  The fins called " ventral," V, supported
by the pelvic hbmapophyses, indicate by their position
the orders of fishes called " abdominal," "thoracic," and
"jugular," by Linnmeus.
The only proper fins in pairs are the "pectoral," P,
answering to the fore-limbs of quadrupeds, and the " ventral," V, answering to the hind-limbs. The rest of the
fins are single and median in position, and are due to
folds of the skin, in which certain dermal bones are




56  STRUCTURE AND FORMULAE OF FIN-RAYS.
developed for their support. These bones are of two
kinds; one, dagger-shaped, are plunged, so to speak, up
to the hilt, in the flesh between the neural spines, and
between the heemal spines; those along the upper surface
of the fish are called " interneural spines," in, Cut 9; those
on the under surface are the "interhmmal spines," ih.
The interneural spines support the " dermoneural spines,
dn, forming the rays of the dorsal fin or fins, D1, D2, and
the upper rays of the caudal fin. The interhkemal spines
support the dermohbemal spines, dh, which form the rays
of the anal fin, A, and the lower rays of the caudal fin,
dh, C.
Both dermoneural and dermohbemal spines may present
two structures; they may be simple, unjointed, firm, bony
spines; or they may be flexible, jointed, and branched
ravys. Those fishes which have one or more of the hard
spines at the beginning of the pectoral, ventral, dorsal,
and anal fins are called "acanthopterygian," or spinyfinned fishes (Gr. acanthos, spine; pterux, fin); those in
which the vertical fins are supported by soft spines are
called "malacopterygian," or soft-finned fishes (Gr. malakos, soft; and pterux). Ichthyologists avail themselves
of the number and kind of rays in the fins to characterize
the species of fishes, and adopt an abbreviated formula
and symbols to express these characters.
In regard to the sea-perch (Fig. 9), the fin-formula
would be as follows:D7,1+ 12: P12: V1 +5: A3+8: C18,
which signifies that D, the dorsal fin, has, in its first division, 7 rays, all spinous; in its second division, 1 spinous
+ (plus) 12 rays that are soft. P, the pectoral fin, has
12 rays, all soft. V, the ventral fin, has one spinous+5




ADAPTATION OF THE FISH'S SKULL, ETC.  57
soft rays. A, the anal fin, has 3 spinous+8 soft rays.
C, the caudal fin, has 18 rays.
When the piscine modification of the vertebrate skeleton is contemplated in relation to the life and movements
of a fish in its native element, every departure from the
archetype is seen to be in direct relation to the habits
and well-being of the species.
The large head has been compared to the embryonic
disproportion of that part in higher vertebrates; but the
head of a fish should be of the size and shape best fitted
to overcome the resistance of water, and to facilitate rapid
progression through that element; the head must, therefore, grow with the growth of the body. Accordingly,
the large skull-bones always show the radiating bony
filaments in their clear circumference, which is the seat
of growth; and hence the number of overlapping squamous sutures which least oppose the progressive extension of the bones. The cranial cavity expands with the
expansion of the skull, but the brain undergoes no corresponding increase; it lies at the bottom of its capacious
chamber, which is principally occupied by a loose cellular
tissue, situated, like the " arachnoid" membrane in man,
between the brain-tunics, called "pia mater" and " dura
mater," and having its cells filled by a light, oily fluid;
thus the head is rendered specifically lighter than if
growth only, and not the modelling absorption also, had
gone on. The loose connection of the hbemal arches and
their parts, including most of what are called " bones of
the face," seems like the retention of a condition observable in the partially-developed skull of the embryos of
higher animals; but this condition is subservient to the
peculiar and extensive movements of the jaws, and of the
bony supports of the breathing machinery. Not any of




58     ADAPTATION OF THE FISH'S SKULL
the limbs of fishes are prehensible; the mouth may be
propelled by them to the food, but the act of taking it
must be performed by the jaws; these can, accordingly,
be not only opened and shut, but can be protruded and
retracted. The division of the long tympanic pedicle into
several partly-overlapping pieces adds to its strength,
and by a slight elastic yielding diminishes the liability to
fracture. The tongue, to judge by its structure, seems to
serve little as an organ of taste, but the arch sustaining it
has much to effect in the way of swallowing; for this
action relates not merely to food; the mechanical part of
breathing is a modified, habitual, and frequent act of deglutition. The hyoid arch is the chief support of the branchial arches and gills; and the branchiostegal membranes,
stretched out upon.the diverging rays of the hyoid arch,
regulate the course and exit of the respiratory currents.
By the retraction of the hyoid arch the opercular doors
are forced open, and the branchial cavity is widened,
whilst all entry from behind is prevented by the branchiostegal flaps, which close the external gill-openings. The
water, therefore, enters by the gaping mouth, and rushes
through the sieve-like interspaces of the branchial arches
into the branchial cavity; the mouth then shuts, the
opercular doors close upon the branchial and hyoid
arches, which again swing forwards; and the branchiostegal membranes being withdrawn, the currents rush out
at the gill-openings. Thus the mechanical functions of
the hbemal arches of the thorax of the higher air-breathing classes are transferred to the haemal arches and appendages of the skull in fishes.
The persistent gills and gill-arches in fishes have been
compared with the same parts which are transitory in
frogs, and with some traces of branchial organization in




TO AQUATIC LIFE.                 59
the embryos of higher vertebrates; and fishes have been
called, in the language of the transmutation-of-species
hypothesis, " arrested gigantic tadpoles."  It will be
found, however, that so far from there having been any
stoppage of development, the branchial arches have been
adapted to the exigencies of the fish by advancing to a
grade of structure which they never reach in the frog.
This is shown by their firm ossification, and their numerous elastic joints; the sieve-like valves developed from
the side next the mouth have been pre-arranged, with the
utmost complexity and nicety of adjustment, to prevent
the entry of any particles of food, or other irritating matters, into the interspaces of the tender, vascular, and
sensitive gills. It is interesting, also, further to observe,
that the last pair of these arches, which, when the embryo-fish is as yet edentulous, usually support gills, are
reduced, when the supply of yolk-food is exhausted, and
the jaws get their prehensile organs, to the capacity of
the gullet, become thickened, in order to support teeth
for tearing in pieces, mincing, or crushing the food, and
are converted into an accessory pair of jaws, and this
pair the most important of the two, as it would seem; for
the carp-tribe-e. g., tench, barbel, roach-which have no
teeth on their proper jaws, have teeth on the pharyngeal
jaws. In no other vertebrate animals, save the osseous
fishes, is the mouth provided with maxillary instruments
at both the fore and hind apertures; and in no other part
of the piscine structure is the direct divergence from any
conceivable progressive scale of ascending organisms,
culminating in man, so plainly marked as in this.
The general form of the fish is admirably adapted to
the element in which it lives and moves. The viscera
are packed in a moderate compass, in a cavity brought




60   ADAPTATION OF THE FISH'S SKELETON.
forwards close to the head. The absence of any neck
gives the advantage of a more extensive and resisting
attachment of the head to the trunk, and a greater proportion of the trunk is left free for the allocation of the
muscular masses whichl move the tail. In the "caudal"
division of the vertebral column, the parapophyses cease
to extend outwards; they bend downwards, unite and
elongate in that direction, proportionally with the elongation of the spines above, whilst dermal and intercalated
spines shoot forth from the middle line above and below,
giving the vertically extended, compressed form to the
hinder half of the body, by the alternating lateral strokes
of which the fish is propelled forwards in the diagonal
between the direction of those forces. The advantage of
the biconcave form of vertebra, with intervening elastic
capsules of gelatinous fluid, in producing a combination
of the resilient with the muscular power, is as obvious as
it is beautiful to contemplate.
The fixation and coalescence of any of the vertebra in
this locomotive part of the fishes' body, analogous to the
part called "sacrum" and "pelvis" in land quadrupeds,
would be a great hindrance to the alternate and vigorous
inflections of that part, by which mainly the fish swims.
A "sacrum" is a consolidation of part of the vertebral
axis of the body, for the transference of more or less of
the weight of that body upon limbs organized for its support on dry land; such a modification would have been
not merely useless, but a hinderance to a fish. The pectoral fins are the prototypes of the fore-limbs of the higher
vertebrates. With their terminal segment, or "hand,"
alone projecting freely from the trunk, and swathed in a
common sheath of skin, they present an interesting analogy to the embryonal buds of the answerable members




TO AQUATIC LIFE.                  61
in man. But what would have been the result if both
arm and forearm had extended freely from the side of the
fish, and dangled as a long many-jointed appendage in
the water! This " higher development," as it is termed,
in relation to the prehensile or cursorial limb of the denizen of dry land, would have been a defect in the structure
of a creature destined to cleave the liquid element. In
the fish, therefore, the fore-limb is left as short as was
compatible with its required functions; the broad manyfingered hand alone projects, but can be applied prone
and flat, by flexion of the wrist, to the side of the trunk;
or it may be extended with its flat surfaces turned forwards
and backwards, so as to check and arrest, more or less
suddenly, the progress of the fish; its breadth can also
be diminished by closing up or stretching out the digital
rays. In the act of flexion, the pectoral fin slightly rotates, and gives an oblique stroke to the water.  The
requisite breadth of the modified hand is gained by the
addition of ten, twenty, or it may be a hundred fingers
over and above the number to which they are restricted
in the forefoot or hand of the higher classes of vertebrata.
The pike maintains a stationary position in a stream by
vibrations of the pectoral fins; the nature of the bottom of
the fish's habitat is ascertained by a tactile application of
the same fins. In the hard-faced gurnards, certain rays
of the pectorals are liberated from the web, and have a
special endowment of nerves, in order to act as feelers.
In the siluroid fishes, the, pectorals wield a formidable
weapon of offence. A tropical species of perch (Anabas)
uses a smaller analogous pectoral spine for climbing up
the mangrove stems in quest of insects.
Certain lophioid fishes, that live on sand-banks left dry
at low water, are enabled to hop after the retreating tide
6




62       ACTION OF THE FINS IN FISHES.
by a special prolongation of the carpal joint of the pectoral fin, which projects in these "frog fishes," as they
have been termed, like the limb of a land quadruped, and
presents two distinct segments clear of the trunk.
The sharks, whose form of body and strength of tail
enable them to swim near the surface of the ocean, are
further adapted for this sphere of activity, and compen.
sated, for the absence of an air-bladder, by the large proportional size of their pectoral fins, which take a greater
share in their active and varied evolutions than in ordinary fishes; more especially in producing that half turn
or roll of the body required to bring the mouth, which is
on the under part of the head, in contact with their prey.
The maximum of development of the many-fingered
hands is attained in the rays, and in those fishes-e. g.,
Exoccetus and Dactylopterus-called "flying fishes," in consequence of the pectorals being long enough, and their
webs broad enough to sustain them in the air, in their
long " flying leaps" out of the water.
With regard to the ventral fins-the rudiments of hindlimbs-these combine merely with the pectorals in raising
the fish, and in preventing, as outriggers, the rolling of'the body during progression. In the long-bodied and
small-headed abdominal fishes the ventrals are situated
near the vent, where they best subserve the office of accessory balancers; in the large-headed thoracic and jugular fishes they are transferred forwards, to aid the pectorals
in supporting and raising the head. If the pectoral and
ventral fins in one of these fishes be cut off, the head
sinks to the bottom; if the right pectoral fin only be cut
off, the fish leans to that side; if the ventral fin on the
same side be cut away, then it loses its equilibrium entirely; if the dorsal and anal fins be cut off; the fish reels




ACTION OF TIHE FINS IN FISHES.             63
to the right and left; when the caudal fin is cut off, the
fish loses the power of progressive motion; when the fish
dies, and the fins cease to play, the belly turns upwards.
Paley thus sums up the actions of the fins of fishes:
"The pectoral, and more particularly the ventral, fins
serve to raise and depress the fish; when the fish desires
to have a retrograde motion, a stroke forward with the
pectoral fin effectually produces it; if the fish desire to
turn either way, a single blow with the tail the opposite
way sends it round at once; if the tail strike both ways,
the motion produced by the double lash is progressive,
and enables the fish to dart forwards with an astonishing
velocity. The result is not only in some cases the most
rapid, but in all cases the most gentle, pliant, easy animal motion with which we are acquainted." " In their
mechanical use, the anal fin may be reckoned the keel;
the ventral fins, the outriggers; the pectoral fins, the
oars;" and we may now add "the caudal fin, the screwpropeller."   And if there be such similitude between
those parts of a boat and a fish, "observe," adds Paley,
"that it is not the resemblance of imitation, but the likeness which arises from applying similar mechanical means
to the same purposes."'
i"Nat. Theology," 8vo., 1805, p. 257.




64    BATRACHIAN ILLUSTRATIONS OF TIIE
PRINCIPAL FORMS OF THE SKELETON IN THE
CLASS REPTILIA.
The transition from fishes to reptiles is easy, and the
signs thereof very manifest in the skeleton.  In the
thorn-back and allied fishes the skull articulates with
the trunk by two condyles, and the part answering to the
basioccipital is a depressed plate. The Batrachia, or lowest order of reptiles-including the siren, proteus, frog,
toad-have a similar double articulation of the skull
with the trunk, the two condyles being developed from
the two exoccipitals. Haemapophyses are not present as
bones in the abdominal part of the trunk of Batrachia,
but they are so developed in the tail. This structure,
with the detachment of the scapular arch from the occiput, and the absence of dermoneural and dermohaemal
spines, serves to distinguish the most fish-like batrachian
from the protopterus and lepidosiren, which are the
most reptile-like of fishes.
In commencing the study of the skeletons of reptiles
in the most fish-like of the class, we find a much less
complex condition of the osseous framework of the body
than in the bony fishes; this will be immediately manifest by a comparison of the skeleton of the menopome
(which may be seen in the Museum, Royal College of
Surgeons, No. 583), as an example of the perennibranchiate batrachia, with the skeleton of the trout (No. 45)
or of the haddock (No. 176, in the same Museum).
The difference tends greatly to elucidate the true nature
of the complexities of the fish's skeleton, since it chiefly
consists in the simplification of that of the. batrachian, by
the non-development of the parts of the dermal skeleton
which characterize that of the fish. The suborbital, super



NATURE OF LIMBS.                  65
orbital, and supratemporal scale-bones are removed, together with the opercular bones, from the head; and the.
interneural and dermoneural spines, with the interhamal
and dermohaemal spines, are removed from the trunk.
The endoskeleton is also reduced to a very simple condition; the advance characteristic of the higher class being
appreciable only by a comparison of it with the skeleton
of the most batrachoid of fishes-e. g. the protopterus
(No. 380).
We then perceive that the bodies of the vertebrae, in
the true batrachian, are distinctly ossified, though preserving, in the perennibranchiate species, a deep, conical,
jelly-filled cavity both before and behind (Cut 11), C; they
Fig. 11.
$ ~,S      - 
SACRAL VERTEBRA AND CONTIGUOUS VERTEBRl-MENOPOME.
have also coalesced with the neural arches, as these have
with their spines, which are, however, scarcely prominent,
except in the tail. The transverse processes are developed
not only from the centrum but from the base of the neural
arch, and are formed by both parapophyses and diapophyses; and they coexist with distinct hwmapophyses in
the tail (ib.), H. With these, likewise, coexist cartilaginous pleurapophyses (ib.), p1, in the second, third, and
6*




66   BATRACHIIAN ILLUSTRATIONS OF LIMBS.
fourth caudal vertebrae; short ossified pleurapophyses
being developed from the ends of the diapophyses in the
first caudal to the vertebra dentata inclusive.
By this instructive condition of the skeleton of the menopome, we perceive at once that the hammapophyses (ib.),
H, are neither transverse processes, nor ribs bent down or
displaced, but are elements of vertebrae, as distinct as the
neurapophyses above. The neural arches are now articulated together by well-developed zygapophyses with synovial articulations, which are absent in the protopterus, as
in most fishes.
In the protopterus, as in the squatina and some other
cartilaginous fishes, the neural arch of the atlas rests
upon a backward production of the basioccipital; in the
batrachians it is confluent with its own proper centrum,
which developes two articular surfaces for the two occipital condyles. The hemal arch of the occipital segment, which is attached to its proper vertebra in the protopterus (Fig. 32), A, 51, 52, as in osseous fishes, is
detached and displaced backwards in the batrachians
(Fig. 33), 51, 52. In the completion of the hbemal arch
of the sacral vertebra in the menopome, by the enlargement of its transverse process (Fig. 11), D, and by its
pleurapophysis (ib.), pi, extended to join a hbemapophysis
(ib.), H, below, we have the key to the essential nature of
the pelvis in all air-breathing animals. The progressive
development of the appendages of the scapular and pelvic
arches, which are to become the four limbs of air-breathing vertebrates, should be traced from their condition in
the protopterus.  Here (Fig. 32) they are reduced to a
single ray, which is soft and many-jointed. In the Am.
phiuma didactyla (Fig, 33) the ray is ossified; its first joint
(ib.), 53, is long, its second (ib.), 54, 55, is bifid, and a car



METAMORPHOSES OF THE FROG'S SKELETON. 67
tilage at the end of this supports two short terminal rays.
This is the pattern of the subdivision of the appendage
both of the scapular and pelvic arches, in all the higher
vertebrates; hence, in consequence of the vast modifications of the several segments, the necessity for their
special names. In the fore-limb the first segment (Fig.
33), 53, is the "arm," and its bone, the "humerus," No.
53; the second segment is the forearm-its two bones
are the "radius," No. 55, and "ulna," No. 54; the third
segment is the "hand"-its rays are the "fingers;" and
its bones are subdivided into "carpals," No. 56, "metacarpals," and "phalanges," No. 57. In the hind-limb
(Fig. 34), the first segment is the " thigh," and its bone,
the "femur," No. 65; the second segment is the "leg,"
and, its two bones are the "tibia," No. 66, and "fibula,"
No. 67; the third segment is the " foot"-its rays are the
"toes;" its bones are subdivided into "tarsals," "metatarsals," and "phalanges."
In the siren, the pelvic arch and limbs are not developed; but they coexist with the scapular arch and
limbs in all other batrachia. In the proteus, the last segment of the fore-limb divides into three rays, that of the
hind-limb into two rays; in other words, it has three
fingers and two toes. The menobranchus has four fingers
and four toes. The axolotl has four fingers and five toes.
The menopome has five fingers and five toes.
The ultimate subdivisions of the radiated or diverging
appendages of the scapular and pelvic arches do not exceed five in any existing air-breathing animal, and their
further complexity is due to the specialization of each
digit, so as to combine in associated action, instead of
their indefinite multiplication, which causes the seeming
complexity of the same appendages in fishes.




68 METAMORPHOSES OF THE FROG'S SKELETON.
In all the fish-like batrachia, called, from a retention of
more or less of the branchial apparatus, "perennibranchia," the limbs are short, and the rays of the
terminal segments of each limb are, more or less, united
by a web; the body is long, and the tail long and compressed. But a great ascent in the scale of life is made
in the batrachian order: all the species when hatched
have the fish-like form, and gills for breathing water;
most of them exist for some time, under this form, in
water; and these undergo so strange a modification of
form and structure before arriving at maturity, that it has
been called a " metamorphosis."  They change their
aquatic for a terrestrial life; they breathe air instead of
water; and from being omniverous become carnivorous.
The tadpoles of our common toad and frog afford ready
and abundant instances for tracing these stages.  The
following is an outline of the main phenomena of the
change observable in regard to the osseous system:In the development of the skeleton of the common
frog, a fibrous and cartilaginous framework is originally
laid down conformably with the aquatic habits and life
of the larva. A large cartilaginous cranium with four
haemal arches, and one of these supporting the framework
of the branchial apparatus-a short series of fibro-cartilaginous vertebrae, minus the haemal arches, in the trunk,
and a series of fibrous septa diverging from the fibrous
capsule of the notochord, and defining and giving attachment to the muscular segments along the tail-constitute
the skeleton of the newly-hatched tadpole. As it grows,
ossification begins; but only in those parts of the skeleton which are to be retained in the future frog. Thus,
the centrums and neurapophyses of the head and trunk
are ossified, but not those of the tail. In the trunk, ossi



METAMORPHOSES OF THE FROG'S SKULL.  69
fication of the vertebral body proceeds centripetally by
layers, successively diminishing in extent, and conical
interspaces are left, consisting of the changed fibrous
capsule of the notochord with the inclosed gelatinous cells,
their liquefied contents forming the balls of fluid, between
the biconcave vertebrae, as in fishes.  But ossification
proceeds to fill up the hinder cavity of the centrum, and
to project into the front cavity of the succeeding vertebra,
with which it is finally connected by a synovial ball-andsocket joint. Thus, the firmer intervertebral articulations
are established, which adapt the vertebral column to the
support of a body which is to be suspended upon limbs,
and transported by them along the surface of the dry
ground. Whilst this change is proceeding, the tail is
undergoing rapid absorption, the retained fibro-cartilaginous condition of its vertebrae rendering them more ready
for removal. In the last fused rudiments of the caudal
vertebrae, ossification extends continuously, and the
peculiar style (Fig. 12), c, at the end of the vertebral
series in the frog and other tailless batrachians, is thus
established.
In the conversion of the biconcave into cup-and-ball
vertebrae in batrachian larvae, ossification commonly, but
not always, proceeds to obliterate the hinder cavity. In
the land salamanders, however, it extends from the front
cavity; so that in the adult vertebrae the ball is anterior,
and the cup posterior, as in certain salamandroid fishes
-e. g., lepidosleuis. In those batrachians that retain more
or less of the branchial apparatus, with the outward form
and natatory tail adapted to aquatic life, the vertebrae of
the tail are ossified like those of the trunk, but the biconcave structure and intervening gelatinous joints are retained throughout life.




70           SKELETON OF THE FROG.
The chief changes which take place in the conversion
of the cartilaginous skull of the larva to the ossified one
Fig. 12.
2
8    56 57
SKELETON OF THE FROG (Rana escuienta).
of the imago, or perfect frog, are seen in the shape and
relative position of the hbemal arches and their appendages-i. e., of the mnaxillary, mandibular, hyoid, and scapular arches. The maxillary arch expands in breadth,




SKELETON OF THE FROG.               71
the mouth widens, and the horny mandibles are shed.
As the mouth advances forwards, the tympanic pedicles
are elongated, and are placed more obliquely; their
proximal end retrograding from the post-frontal to the
mastoid region of the skull, and their distal end inclining
forwards with the attached lower jaw, Nos. 29, 33, on
which the denticles now begin to be developed. For the
still more extraordinary changes of the hyoid arch, No.
41, and its branchial appendages, No. 46, the student is
referred to Dzugk's Recherches sur l'Osteologie des Batraciens, 4to., 1835; and to the writer's Archetype of the Vertebrate Sk7eleton, pp. 70, 71.
The scapular arch, which was close to the occiput,
whilst protecting and supporting the branchial heartits primary function —begins, as the rudiments of the
fore-limbs bud out, to recede backwards, like the mandibular and branchial arches, but to a greater extent, the
attachment to the occipital segment being wholly 16st.
The scapular and coracoid portions of the arch become
first ossified; the suprascapular plate remains long cartilaginous, and always partly so; the sternum is developed
in proportion as the hyoid arch is reduced, and the branchial arches are removed; thus a strong fulcrum is completed for the articulation of the shoulder-joints. The
pelvic arch had previously been completed, and the iliac
bones and sides of the sacrum become coelongated: then
the ilia continue to extend backwards as the tail is being
absorbed, and the hind-limbs are lengthened out and
finished.
Thus metamorphosed, the skeleton of the frog presents the following structure (Fig. 12): The number of
vertebrae of the trunk, exclusive of the coxygeal style, c,
is nine; the first, or atlas, has no diapophyses, but these




72           SKELETON OF THE FROG.
are present and long on the rest, especially on the third,
d, and ninth, s, vertebrae; in the latter they are thick,
stand outwards, and support two other long, curved, riblike bones, 62, which expand at their distal ends, and
unite to two bony plates, 63, completing the haemal arch
of.the ninth segment of the trunk. The bones of the
hinder extremities are attached to the point of union of
the above costal and hbemal pieces, one of which answers
to the ilium, 62, and the other to the isehium, 63. The
superior development of this arch relates to the great
size and strength of the hinder extremities in the tailless
tribe.  The bodies of the vertebrae are articulated by
ball-and-socket joints, the cup being anterior, the ball
posterior, a modification which relates to the more terrestrial habits and locomotion of these higher-organized
batrachia. The caudal vertebrae are represented by a
single, elongated, cylindrical style, c, having an anchylosed neural canal. In the seven vertebrae, between the
atlas and the sacrum, two zygapopophyses, looking upwards, two zygapophyses, z, looking downwards, and a
short spine, are developed from each neural arch.
The suprascapula, 50, is very broad, and in great part
ossified; the scapula, 51, divides at its humeral end into
an acromial and coracoid process; the latter articulates
with the true coracoid bone, 52, the acromion with the
expanded extremity of the clavicle, 58: the glenoid
cavity is formed by both the scapula and the coracoid.
An episternal bone, 59, supporting a broad cartilage, is
articulated to the mesial union of the clavicles, from
which a bony bar is continued backwards between the
expanded and partially conjoined ends of the coracoids.
The sternum, 60, is articulated to the posterior part of




SKELETON OF THE FROG.                 73
the same extremities of the coracoids, and supports a
broad " xiphoid" cartilage.
The proximal end of the humerus, 53, is an epiphysis;
the distal end presents a hemispherical ball between a
small external ridge, and a large internal condyloid process. The antibrachial bones have coalesced, but an
anterior and posterior indentation at the distal half indicates the radius, 55, and ulna, 54; their distal articular
extremities are represented by a single epiphysis. The
ulnar portion of the bone develops a short and broad
olecranon, o. The bones of the carpal series now receive
definite names, and are as follows: (Fig. 12), s, scaphoid; 1, lunare; c and p, cuneopisiforme; t, trapezium;
tr, trapezoides; mr, magnum; i, unciforme-here two
distinct bones. The first digit, I, has one bone, a metacarpal; the second digit, II, has a metacarpal and two
phalanges; the third, III, the same; the fourth, IV, has
a metacarpal and three phalanges; and the fifth, V, the
same.
Both the proximal and the distal extremities of the
femur, 65, are in the condition of epiphyses. The tibia
and fibula are connate, 66: a longitudinal impression on
the front and back part of the expanded distal end indicates their division, but a single epiphysis, partially anchylosed, forms the proximal extremity, and a similar
one the distal extremity, of the connate bones; they are
perforated near their middle, from before backwards, by
a vascular canal. The tarsal bones are now distinguished
by names.
The astragalus, a, and calcaneum, cl, are much elongated;
the former is slightly bent, the latter straight; they have
coalesced at their proximal and also at their distal extremities with each other, and with the scaphoid, s, and
7




ob




cuboid,  b, bones. Three cuneiform bones, c, ci. remain
detached, and immediately support the three inner toes
and a cartilaginous appendage.  The first toe, i, and
second toe, ii, have each a metatarsal and two phalanges;
the third toe, iii, has a metatarsal and three phalanges;
the fourth toe, iv, has a metatarsal and four phalanges;
the fifth toe, v, a metatarsal and three phalanges. The
great length and strengh of the pelvic arch, and its appendages, the hind-limbs, give the frog the power of executing the long leaps for which it is proverbial.
All the batrachia present this structure in common with
fishes, viz., that the ribs of the trunk, when present; are
free, consist only of "pleurapophyses," and do not encompass the thoracic-abdominal cavity. The absence of
unyielding osseous girdles at this part seems to relate to
a peculiarity of their generation, viz: the almnost simultaneous ripening of the sperm-cells and ova, causing a
great and sudden distension of the abdomen at the breeding period.
OSTEOLOGY OF TIIE OPHIDIA, OR SERPENT
TRIBE.
There are certain tropical land batrachia-the Cecilime,
of the ear-chamber; in the basioccipital combining with




76  STRUCTURE OF TItE SKULL IN SERPENTS.
tween the elongated parietals and the sphenoid; in the
constant coalescence of the parietals with one another; in
the constant confluence of the orbitosphenoids with the
frontals, and in the meeting of the orbitosphenoids below
the prosencephalon, upon the upper surface of the presphenoid; in the presence of distinct postfrontals, and the
attachrnent thereto of the ectopterygoids, whereby they
form an anterior point of suspension of the lower jaw,
through the medium: of the pterygoid and tympanic
bones; lastly, in the connation of the prefrontals and lachrymals.
In studying the osteology of the head of the python,
as the type of the Ophidian Order, by the aid of the following description, the student may compare the disarticulated skull, No. 628, with that of the large skeleton,
No. 602, in the Museum, Royal College of Surgeons: the
bones are numbered as here referred to.
The basioccipital, 1, is subdepressed, broadest anteriorly, subhexagonal; smooth and concave at the middle
above, with a rough sutural tract on each side, and a
hypapophysis below, produced into a recurved point. The
hinder facet of the basioccipital is convex, forming the
lower half of the occipital condyle, which is supported on
a short peduncular prolongation. The basioccipital unites
above and laterally with the exoccipitals and alisphenoids, and in front with the basisphenoid, upon which it
rests obliquely, and it supports the medulla oblongata on
its upper smooth surface.
The exoccipitals, 2, 2, are very irregular subtriangular
bones; each is produced backwards into a peduncular
process, supporting a moiety of the upper half of the occipital condyle. The outer and fore part of the exoccipital expands into the irregular base of the triangle:
P  p                                    0




STRUCTURE OF THE SKULL IN SERPENTS. 77
it is perforated by a slit for the eighth pair of nerves; it
articulates below with the basioccipital; it is excavated
in front to lodge the petrosal cartilage, where it articulates
with the alisphenoid; it unites above with the superoccipital. The superoccipital, 3, is of a subrhomboidal form,
sends a spine from its upper and hinder surface, expands
laterally into oblong processes, is notched anteriorly, and
sends down two thin plates from its under surface, bounding on the mesial side the surface for the cerebellum, and
by the outer side forming the inner and upper parts of
the acoustic cavities. The superoccipital articulates below
with the exoccipitals and alisphenoids, and in front with
the parietal, by which it is overlapped in its whole extent.
The occipital vertebra is as if it were sheathed in the expanded posterior outlet of the parietal one (Fig. 17), the
centrum resting on the oblique surface of that in front,
and the anterior base of the neural spine entering a cavity
in and being overlapped by that of the preceding neural
spine: the analogy of this kind of " emboitement" of the
occipital in the parietal vertebra with the firm interlocking of the ordinary vertebrae of the trunk is very interesting: the end gained seems to be, chiefly, an extra
protection of the epencephalon —the most important segment to life of all the primary divisions of the cerebrospinal axis. The thickness of its immediately protecting
walls (formed by the basi, ex, and superoccipitals) is
equal to that of the same vertebral elements in the human
skull; but they are, moreover, composed of very firmn and
dense tissue throughout, having no diplod: the epencephalon also derives a further and equally thick bony covering
from the basisphenoid and the parietals, the latter being
overlapped by the mastoids, which form a third covering
to the cerebellum.
7*




78  STRUCTURE OF TEE SKULL OF THE PYTHON.
The basisphenoid, 5, and presphenoid, 9, form a single
bone, and the chief keel of the cranial superstructure.
The posterior articular surface looks obliquely upwards
and backwards, and supports that of the vertebral centrum
behind, as the posterior ball of the ordinary vertebrae
supports the oblique cup of the succeeding vertebrae;
here, however, all motion is abrogated between the two,
vertebrae, and the coadapted surfaces are: rough and:
sutural. The basisphenoid presents a smooth cerebral:
channel above- for the mesencephalon, in front of which a!
deep depression (sella) sinks abruptly into the expanded'
part of the bone, and there bifurcates, each fork forming
a short cul-de-sac in the substance of the bone.
The alisphenoids, 6, form: the anterior half of the fenestra ovalis, which is completed by the exoccipitals; and
in their two large perforations for the posterior divisions
of the fifth pair of nerves, as well as in their relative size:
and position, the alisphenoids agree with those of the frog.
Each alisphenoid is: a thick suboval piece, with a tubercular process on its under and lateral part; it rests upon
the basisphenoid and basioccipital, supports the posterior
part of the parietal and a portion of the mastoid, 8, and
unites anteriorly with the descending lateral plate of the
parietal bone.
-The parietal, 7, is a large and long, symmetrical, roofshaped bone, with a median longitudinal crest along its
upper surface, where the two originally distinct moieties
have coalesced. It is narrowest posteriorly, where it
overlaps the superoccipital, and is itself overlapped by
the mastoid: it is convex at its middle part on each side
of the sagittal spine, and is continued downwards and inwards, to rest immediately upon the basisphenoid. This
part of the parietal seems to be formed by an extension




STRUCTURE OF THE SKULL OF THE PYTIION. 79
of ossification along a membranous space, like that which
permanently remains so in the frog, between the alisphenoid and orbitosphenoid: the mesencephalon and the chief
part of the cerebral lobes are protected by this unusually
developed spine of the mesencephalic vertebra. The
optic foramina are conjugational ones, between the anterior border of the lateral plate- of the parietal and the
posterior border of the corresponding plate of the frontal.
Theifrontals, 11, rest by descending lateral plates, representing connate orbitosphenoids, 12, upon the attenuated, pointed prolongation of the basisphenoid: the upper
surface of each frontal is flat, subquadrate,- broader than
long in the boa, and the reverse in the python, where the
roof of the orbit is continued outwards by a detached superorbital bone: there is a distinct, oval, articular surface near
the anterior median angle of each frontal to which the
prefrontal is attached: the angle itself is slightly produced,
to form the articular process for the nasal bones. The
smooth orbitosphenoid plate of the frontal joins the outer
margin of the upper surface of the frontal at an acute
angle; the inner side of each frontal is deeply excavated
for the prolongation of the cerebral lobes, and the cavity
is converted into a canal by a median vertical plate of
bone at the inner and anterior end of the frontal. The
frontals join the parietals and postfrontals behind, and,
by the anchylosed orbital plates, the presphenoid below,
the prefrontals and nasals before, and the superorbitals at
their lateral margins. The orbitosphenoids have their
bases extended inwards, and meet below the prosencephalon and above the presphenoid, as the neurapophyses
of the atlas meet each other above the centrum. The
anterior third part of such inwardly-produced base is met
by a downward production of the mesial margin of the




80 STRUCTURE OF THE SKULL OF THE PYTHON.
frontal, forming a septum between the olfactory prolongations of the brain, but is not confluent with the frontal
bone: the outer portion of the orbitosphenoids ascends
obliquely outwards, and is confluent with the under part
of the frontal; it is smooth externally, and deeply notched
posteriorly for the optic foramen.
The post-frontal, 12, is a moderately long trihedral bone,
articulated by its expanded cranial end to the frontal and
parietal, and bent down to rest upon the outer and fore
angle of the ectopterygoid. It does not reach that bone
in the boa, nor in poisonous serpents. In both the boa
and python, it receives the anterior sharp angle of the
parietal in a notch.
The natural segment which terminates the cranium anteriorly, and is formed by the vomerine, prefrontal, and
nasal bones, is very distinct in the ophidians.
The vomer, 13, is divided, as in salamandroid fishes
and batrachians, but is edentulous: each half is a long,
narrow plate, smooth and convex below, concave above,
with the inner margin slightly raised; pointed anteriorly,
and with two processes, and an intervening notch above
the base of the pointed end. The prefrontals, 14, are
connate with the lachrymals, 73. The two bones which
intervene between the vomerine and nasal bones are the
turbinals, 19; they are bent longitudinally outwards in
the form of a semicylinder about the termination of the
olfactory nerves.
The spine of the nasal vertebra is divided symmetrically, as in the frog, forming the nasal bones, 15; they are
elongated, bent plates, with the shorter upper part arching
outwards and downwards, completing the olfactory canal
above, and with a longer median plate, forming a vertical
wall, applied closely to its fellow, except in front, where




SKULL OF THE BOA CONSTRICTOR.             81
the nasal process of the premaxillary is received in the
interspace of the nasals.
The acoustic capsule remains in great part cartilaginous;
there is no detached centre of ossification in it; to whatever extent this capsule is ossified, it is by a continuous
extension from the alisphenoid. The sclerotic capsule of
the eye is chiefly fibrous, with a thin inner layer of cartilage; the olfactory capsule is in a: great measure ossified,
as above described.
MAXILLAIRY ARCH.
The palatine, 20, or first piece of this arch, is a strong,
oblong bone, having the inner side of its obtuse anterior
end applied to the sides of the prefontals and turbinals,
and, near its posterior end, sending a short, thick process
upwards and inwards for ligamentous attachment to the
lachrymal, and a second similar process outwards as the
point of suspension of the maxillary bone. Between these
processes the palatine is perforated, and behind them it
terminates in a point. The
chief part of the maxillary, 21        Fig. 14.
(Fig. 14), is continued forwards                 21
from its point of suspension, 282
increasing in depth, and termi- 28
nating obtusely; a shorter process is also, as usual, continued    SKULL OF BOA CONSTRICTOR.
backwards, and terminates in
a point. The point of suspension of the maxillary forms
a short, narrow, palatine process. A space occupied by
elastic ligament intervenes between the maxillary and the
premaxillary, 22, which is single: and symmetrical, and




82      SKULL OF THE BOA CONSTRICTOR.
firmly wedged into the nasal interspace; the anterior expanded part of this small triangular bone supports two
teeth. Thus, the bony maxillary arch is interrupted by
two ligamentous intervals at the sides of the premaxillary
key-bone, in functional relation to the peculiar independent movements of the maxillary and palatine bones required by serpents during the act of engulfing their usually
large prey. Two bones extend backwards as appendages
to the maxillary arch: one is the " pterygoid," 24, from
the palatine; the other the ectopterygoid, 25, from the
maxillary. The pterygoid is continued from the posterior
extremity of the palatine to abut against the end of the
tympanic pedicle; the under part of the anterior half of
the pterygoid is beset with teeth. The ectopterygoid, 25,
overlaps the posterior end of the maxillary, and is articulated by its posterior-obliquely cut end to the outer
surface of the middle expanded part of the pterygoid.
MANDIBULAR ARCHI.
The tympanic bone, 28 (Figs. 14 and 15), is a strong
trihedral pedicle, articulated by an oblique upper surface
to the end of the mastoid, and expanded transversely
below to form the antero-posteriorly convex, transversely
concave, condyle for the lower jaw. This consists chiefly
of an articular and a dentary, with a small coronoid and
splenial, piece. The articular piece ends obtusely, immediately behind the Condyle; it is a little contracted in
front of it, and gradually expands to its middle part,
sends up two short processes, then suddenly contracts
and terminates in a point wedged into the posterior and
outer notch of the dentary piece. The articular is deeply




SKULL OF THE BOA CONSTRICTOR.           83
grooved above, and produced into a ridge below. The
coronoid is a short compressed plate; the splenial is a
longer, slender plate, applied to the inner side of the
articular and dentary, and closing the groove on the
inner side of the latter. The outer side of the dentary
offers a single perforation near its anterior end, which is
united to that of the opposite ramus by elastic ligament.
By the above-described mode of union of the extremities of the maxillary and mandibular bones, those on the
right side can be drawn apart from those on the left, and
the mouth can be opened not only vertically, as in other
vertebrate animals, but also transversely, as in insects.
Viewing the bones of the mouth that support teeth in
the great constricting serpents, they offer the appearance
of six jaws-four above and two below; the inner pair
of jaws above are formed by the palatine and pterygoid
bones, the outer pair by the maxillaries, the under pair
by the mandibles, or "rami," as they are termed, of the
lower jaw.
Each of these six jaws, moreover, besides the movements vertically and laterally, can be protruded and retracted, independently of the other: by these movements
the boa is enabled to retain and slowly engulf its prey,
which may be much larger than its own body. At the
first seizure, the head of the prey is held firmly by the
long and sharp recurved teeth of all the jaws, whilst the
body is crushed by the overlapping coils of the serpent;
the death-struggles having ceased, the constrictor slowly
uncoils, and the head of the prey is bedewed with an
abundant slimy mucus: one jaw is then unfixed, and its
teeth withdrawn by being pushed forward, when they
are again infixed, further back upon the prey; the next
jaw is then unfixed, protruded, and reattached; and so




81-      SKULL OF POISONOUS SERPENTS.
with the rest in succession-this movement of protraction being almost the only one of which they are susceptible whilst stretched apart to the utmost by the bulk
of the animal encompassed by
Fig. 15.       them; thus, by their successive
28       s          movements, it is slowly and:spirally introduced  into the
wide gullet.
The bones of the mouth, in
SKULL OF A POISONOUS SNAKE. the poisonous serpents, have
characters distinct from those
of the constricting serpents. These characters consist
chiefly in the modification of form and attachments of
the superior maxillary bone (Fig. 15), 21, which is movably articulated to the palatine, ectopterygoid, and lachrymal bones; but chiefly supported by the latter; which
presents the form of a short, strong, three-sided pedicle,
extending from the anterior external angle of the frontal
to the anterior and upper part of the maxillary. The
articular surface of the maxillary is slightly concave, of
an oval shape; the surface articulating with the ectopterygoid on the posterior and upper part of the maxillary
is smaller and convex. The maxillary bone is pushed
forward and rotated upon the lachrymal joint by the advance of the ectopterygoids, which are associated with
the movements of the tympanic pedicle of the lower jaw
by means of the true pterygoid bones. The premaxillary bone (Fig. 13), 22, is edentulous. A single, long,
perforated poison-fang is anchylosed to the right maxillary, and sometimes two similar fangs, as in the cobra
figured in Cut 13. The palatine bones have four or five,
and the pterygoids from eight to ten small, imperforate,
pointed, and recurved teeth. The frontal bones are




VERTEBRiE OF THE RATTLESNAKE.              85
broader than they are long; there are no superorbitals.
A strong ridge is developed from the under surface of
the basisphenoid, and a long and strong recurved hypapophysis from that of the basioccipital; these give insertion to the powerful " longi-colli" muscles, by which the
downward stroke of the head is performed in the infliction of the wound by the poison-fangs.
The characteristics of the trunk-vertebrse of the ophidian reptiles are as follows: The autogenous elements,
except the pleurapophyses (Fig. 16), pl, coalesce with
one another in the vertebrae of the trunk; and the pleurapophyses also become anchylosed to the diapophyses
in those of the tail. There is no trace of suture between
the neural arch (ib.), n, and centrum, c. The outer substance of the vertebra is compact, with a smooth or
polished surface.  The vertebrae are
"procoelian;" that is, they are articu-    Fig. 16.
lated together by ball-and-socket joints,    nt
the socket being on the fore part of the
centrum, where it forms a deep cup    n- 
with its rim sharply defined; the cavity
looking not directly forwards, but a   --       p
little downwards, from the greater prominence of the upper border; the well-  VERTEBRA OF THE
turned prominent ball terminates the RATTESAE (Crotaback part of the centrum rather more
obliquely, its aspect being backwards and upwards.
The hypapophysis, hy, is developed in different proportions from different vertebrae, but throughout the greater
part of the trunk presents a considerable size in the
cobra and crotalus (Figs. 13 and 16), hy; it is shorter in
the python and boa. A vascular canal perforates the
under surface of the centrum, and there are sometimes
8




86           VERTEBRIE OF SERPENTS.
two or even three smaller foramina. In the python, a
large, vertically oblong, but short diapophysis extends
from the fore part of the side of the centrum obliquely
backwards: it is covered by the articular surface for the
rib, convex lengthwise, and convex vertically at its
upper half, but slightly concave at its lower half. In
the rattlesnake, the diapophysis develops a small, circumscribed, articular tubercle, d, for the free vertebral
rib or pleurapophysis, pl; a parapophysis, p, extends
downwards and forwards below the level of the centrum;
the anterior zygapophysis, z, se6ms to be supported by a
similar process from the upper end of the diapophysis.
The base of the neural arch swells outward from its confluence with the centrum, and develops from each angle
a transversely-elongated zygapophysis; that from the
anterior angle looking upwards, that from the posterior
angle downwards, both surfaces being flat, and almost
horizontal, as in the batrachians. The neural canal is
narrow; the neural spine, ns, is of moderate height,
about equal to its antero-posterior extent; it is compressed and truncate.  A  wedge-shaped process (the
"zygosphene"), zs, is developed from the fore part of the
base of the spine; the lower apex of the wedge being, as
it were, cut off, and its sloping sides presenting two
smooth, flat, articular surfaces. This wedge is received
into a cavity (the "zygantrurn") excavated in the posterior expansion of the neural arch, and having two
smooth articular surfaces to which the zygosphenal surfaces are adapted.
Thus the vertebrae of serpents articulate with each
other by eight joints in addition to those of the cup and
ball on the centrum; and interlock by parts reciprocally
receiving and entering one another, like the joints called




VERTEBRAE OF SERPENTS.              87
tenon-and-mortise in carpentry. In the caudal vertebrae,
the hypapophysis is double, the transition being effected
by its progressive bifurcation in the posterior abdominal
vertebrae. The diapophyses become much longer in the
caudal vertebra, and support in the anterior ones short
ribs which usually become anchylosed to their extremities.
The pleurapophyses or vertebral ribs in serpents have
an oblong articular surface, concave above and almost flat
below in the python, with a tubercle developed from the
upper part, and a rough surface excavated on the fore
part of the expanded head for the insertion of the precostal ligament. They have a large medullary cavity,
with dense but thin walls, and a fine cancellous structure
at their articular ends. Their lower end supports a short
cartilaginous haemapophysis, which is attached to the
broad and stiff abdominal scute. These scutes, alternately
raised and depressed by muscles attached to the ribs and
integument, aid in the gliding movements of serpents;
and the ribs, like the legs in the centipede, subserve locomotion; but they have also accessory functions in relation
to breathing and constriction. The anterior ribs in the
cobra (Fig. 13), pl, are unusually long, and are slightly
bent; they can be folded back one upon another, and can
be drawn forward, or erected, when they sustain a fold of
integurment, peculiarly colored in some species-e. g. the
spectacled cobra-and which has the effect of making
this venomous snake more conspicuous at the moment
when it is about to inflict its deadly bite. The ribs commence in the cobra, as in other serpents, at the third vertebra from the head.
The centrum of the first vertebra coalesces with that
of the second, and its place is taken by an autogenous




88           VERTEBRAE OF SERPENTS.
hypapophysis: this, in the python, is articulated by suture
to the neurapophyses; it also presents a concave articular
surface anteriorly for the lower part of the basioccipital
tubercle, and a similar surface behind for the detached
central part of the body of the atlas, or "odontoid process of the axis." The base of each neurapophysis has
an antero-internal articular surface for the exoccipital
tubercle, the middle one for the hyapophysis, and a
postero-internal surface for the upper and lateral parts of
the odontoid; they thus rest on both the separated parts
of their proper centrum. The neurapophyses expand
and arch over the neural canal, but meet without coalescing. There is no neural spine. Each neurapophysis develops from its upper and hinder border a short zygapophysis, and from its side a still shorter diapophysis.
In the second vertebra, the odontoid presents a convex
tubercle anteriorly, which fills up the articular cavity in
the atlas for the occipital tubercle; below this is the surface for the hypapophysial part of the atlas, and above
and behind it are the two surfaces for the atlantal neurapophyses. The whole posterior surface of the odontoid
is anchylosed to the proper centrum of the axis, and in
part to its hypapophysis. The neural arch of the axis
develops a short ribless diapophysis from each side of
its base; a thick sub-bifid zygapophysis from each side of
the posterior margin; and a moderately long bent-back
spine from its upper part. The centrum terminates in a
ball behind, and below this sends downwards and backwards a long hyapophysis.
At the opposite extreme of the elongated body, two or
three much simplified vertebrae are usually found blended
together. In true serpents there are no scapular arch and
appendages, no sternum, no sacrum; but a pair of slender




VERTEBRA OF SERPENTS.                 89
bones, often supporting a second bone, armed with a claw,
are found suspended on the flesh near the vent. The exposed parts of these appendages are called " anal hooks;"
the parts themselves, like the similarly suspended ventral
fins of the pike, are rudiments of hind limbs.
Serpents have been regarded as animals degraded from
a higher type; but their whole organization, and especially
their bony structure, demonstrate that their parts are
as exquisitely adjusted to the form of their whole, and to
their habits and sphere of life, as is the organization of
any animal which we call superior to them. It is true
that the serpent has no limbs, yet it can outclimb the
monkey, outswim  the fish, outleap the jerboa, and, suddenly loosing the close coils of its crouching spiral, it
can spring into the air and seize the bird upon the wing:
all these creatures have been observed to fall its prey.
The serpent has neither hands nor talons, yet it can outwrestle the athlete and crush the tiger in the embrace of
its ponderous overlapping folds. Instead of licking up
its food as it glides along, the serpent uplifts its crushed
prey, and presents it, grasped in the death-coil as in a
hand, to its slimy gaping mouth.
It is truly wonderful to see the work of hands, feet,
and fins performed by a modification of the vertebral
column-by a multiplication of its segments with mobility
of its ribs. But the vertebra  are specially modified, as
we have seen, to compensate, by the strength of their
numerous articulations, for the weakness of their manifold repetition, and the consequent elongation of the
slender column. As serpents move chiefly on the surface
of the earth, their danger is greatest from pressure and
blows from above; all the joints are fashioned accordingly
to resist yielding, and sustain pressure in a vertical direc



90 SECTION OF THE BOA CONSTRICTOR'S SKULL.
tion; there is no natural undulation of the body upwards
and downwards-it is permitted only from side to side.
So closely and compactly do the ten pairs of joints between each of the two hundred or three hundred vertebrae
fit together, that even in the relaxed and dead state the
body cannot be twisted except in a series of side coils.
In the construction of the skull, which has merited a description in some detail, and well deserves a close study,
the thickness and density of the cranial bones must strike
the mind as a special provision against fracture and injury
to the brain. When we contemplate the still more remarkable manner in which these bones are applied, one
over another, the superoccipital (Fig. 17), 3, overlapping
Fig. 17.
v ade t
SECTION OF SKULL, BOA CONSTRICTOR.
the exoccipital, 4, and the parietal, 7, overlapping the
superoccipital-the natural segments or vertebrae of the
cranium being sheathed, one within the other, like the
corresponding segments in the trunk —we cannot but
discern a special adaptation in the structure of serpents
to their commonly prone position, and a provision, exemplified in such structure, of the dangers to which they
would be subject from falling bodies and the tread of
heavy beasts. Many other equally beautiful instances of
design might be cited from the organization of serpents,
in relation to the necessities of their apodal vermiform




VERTEBRE, ANI) SKULL OF TIHE LIZARD.  91
character; just as the snake-like eel is compensated by
analogous modifications amongst fishes, and. the snakelike centipede among insects.
OSTEOLOGY OF LIZARDS.
The transition from the ophidian, or snake-like, to the
lacertian, or lizard-like reptiles, is very gradual and easy,
if we pass from the serpents with fixed jaws and a scapular arch-as, e. g. the slow-worms (anguis)-to the serpentiform lizards with mere rudiments of limbs-as, e. g.
the pseudopus. The distinction is effected through the
establishment of a costal arch in the trunk, completed by
the addition of a haemal spine (sternum) and hemapophyses (sternal ribs) to the pleurapophyses or vertebral ribs,
which are alone ossified in ophidia.
The vertebrae of the trunk have the same proccelian
character, i. e. with the cup anterior and the ball behind;
the latter being usually less prominent, more oblique, and
more transversely oval than in serpents. The vertebrae
also are commonly larger, and always fewer in number
than in the typical ophidia. The ribs do not begin to be
developed so near the head in lizards. Not only the atlas
and dentata, but sometimes, as in the monitor (varanus),
the four following vertebrae are devoid of pleurapophyses;
and when these first appear they are short, and sometimes
(as in cyclodus) expanded at their extremities. They rapidly elongate in succeeding vertebrae, and usually at the
ninth from the head (cyclodus, iguana), or tenth (varanus),
they are joined through the medium of ossified haemopophyses to the sternum; two (varanus), three (chameleo,
iguana), or four (cyclodus), following vertebrae are simi



92   VEIRTEPBRY ANTD SKULL OF THE LIZARD.
larly completed; and then the haemapophyses are either
united below without intervening sternum (chanmeleo), or
two or three of them are joined by a common cartilage to
the cartilaginous end of the sternum. The haemapophyses
afterwards project freely, and are reduced to short appendages to the pleurapophyses. These also shorten, and
sometimes suddenly, as, e. g. after the eighteenth vertebra
in the monitors (varanus), in which they end at the twenty-eighth vertebra, as they began, viz: in the form of
short straight appendages to the diapophyses.
The flying lizard (Draco volans), is so called on account
of the wing-like expansions from the side of its body, supported, like the hood of the cobra, by slender elongated
ribs. In this little lizard there are twenty vertebrae supporting movable ribs, which commence apparently at the
fifth. Those of-the eighth vertebra first join the sternum,
as do those of the ninth and tenth; the pleurapophyses of
the eleventh vertebra suddenly acquire extreme length;
those of the five following vertebrae are also long and
slender; they extend outwards and backwards and support the parachute formed by the broad lateral fold of
the abdominal integuments. The pleurapophyses of the
seventeenth vertebra become suddenly shorter, and these
elements progressively diminish to the sacrum; this consists of two vertebrae, modified as in other lizards. There
are about fifty caudal vertebrae.
The semi-ossified sternum in the iguana has a median
groove and fissure, and readily separates into two lateral
moieties. The long stem of the episternum  covers the
outer part of the groove, where it represents the keel of
the sternum in birds.
In the skull of the lizard order we first meet with a
second bony bar, diverging from the maxillary arch back



VERTEBRA] AND SKULL OF THE LIZARD. 93
wards, and abutting against the mastoid, and sometimes
also against the tympanic and postfrontal. This bar is
called the "zygomatic arch;" it usually consists of two
bones-the one next the maxillary is the "malar," 26,
the one next the mastoid is the "squamosal," 27; it
assumes a form meriting that name in the tortoise, and
first received it, as "pars squarnosa," in man, where it is
not only like a great scale, but becomes confluent with
both the mastoid and tympanic. But, as has been before
remarked, we must use the terms invented by anthropotomists as arbitrary signs of the corresponding bones in
the lower creation.
The scapula in the monitor (varanus) is a triangular
plate with a convex base, a concave hind border, and a
nearly straight front border; the apex is thick and truncate, with an oval surface divided into two facets. The
hind border forms a part of the glenoid cavity; the front
one is a rough epiphysial surface, continuous with a
similar but narrower tract, extending upon the anterior
border, and by which the scapula articulates with the
coracoid. In the iguanians and scincoids this synchondrosis is obliterated, and the two bones are confluent.
The hind border of the scapula is nearly straight-the
front one sends forwards a process dividing it into two
deep marginations.
The coracoid in both the varanus and iguana is short
and broad; its main body, which articulates with the
sternum, is shaped like an axe-blade; and two strong,
straight, compressed processes extend forwards from its
neck, which is perforated between the origins of these
processes and the part forming the glenoid articulations.
The clavicles are simple sigmoid styles in the varanus
and iguana; are bent upon themselves, like the Australian




94   VERTEBRAE  AND SKULL OF THE LIZARD.
boomerang, in the cyclodus; and have the median part of
the bend expanded and perforated in lacerta and scineus.
They are absent in the chameleon.
The sacral vertebrae retain, in some lacertians, the cupand-ball joints; and in these, e. g. the scincoids-in which
the centrums coalesce, the hind end of the second presents
a ball to the first caudal-not a cup, as in the crocodile.
In the cyclodus, the thick, short, straight pleurapophyses
are distinct at their origins from the two coalesced centrums, but coalesce at their ends, that of the first sacral
being the thickest. In varanus and iguana, the pleurapophyses as well as the centrums, retain their distinctness,
but the hinder ribs incline forwards and touch the expanded ends of the fore pair. These ends are very thick,
and are scooped out obliquely behind, so as to present a
curved border to the ilium, which Cuvier compares to a
horseshoe.
In the varanus and iguana, the pleurapophyses of the
first caudal incline backwards as much as those of the
second sacral do forwards. In the cyclodus they extend
outwards, parallel with those of the sacral vertebrae, and
are longitudinally grooved beneath. IHsemapophyses are
wanting in the first caudal, are developed in the second,
and are displaced to the interval between this and the
third; they are confluent at their distal end, and produced into a long spine. At the twelfth tail-vertebra, the
line is obvious that indicates the extent of the anterior
detached piece, or epyphysis, of the centrum, immediately
in front of the origin of the diapophyses; it continues
marking off the anterior third of the centrum in all the
other caudals. At this line the tail snaps off, when a
lizard escapes by the common ruse of leaving the part of
the tail by which it had been seized in the hands of the




SKELETON OF THE CROCODILE.                 95
baffled pursuer. It is a very curious character, and quite
peculiar to the lacertians-this ossification of the centrumr
from two points and their incomplete coalescence: it adds
nothing to the power of bending, or to any other action
of the tail, but indicates a prevision of the liability to
their being caught by their long tail, and may be interpreted as a provision for their escape. The neural arch
has coalesced with the centrum throughout the tail; the
epiphysial line does not extend through that arch; but
its thin and brittle walls soon break, when the two parts
of the centrum are forcibly separated.
Lizards, as is well known, have the power of reproducing the tail, but the vertebral axis is never ossified in the
new-formed part.
OSTEOLOGY OF CROCODILES.
The numerous and varied forms of fossil bones of extinct reptiles derive most elucidation from the skeleton
of the higher organized sauria of Cuvier, which now are
rightly held to constitute a distinct order, called Loricata,
or Crocodilia; a more complete description, therefore, will
be given of the skeleton of a member of this order, than
was deemed needful in regard to the lacertian group of
sauria.
Fig. 18.. —-------------
--   -  6  -,
- --                 6 
SKELETON OF THE CROCODILE (CrocodilLUs iloticlls).




96        VERTEBRAE OF THE CROCODILE.
Commencing with the trunk, the first and second vertebrse of the neck are peculiarly modified in most airbreathing vertebrata, and have acFig. 19.      cordingly received the special names,
the one of " atlas," the other of" axis."
In comparative anatomy these become arbitrary terms, the properties
being soon lost which suggested
aY/t'    those names to the human anatoATLAS AND AXIS VERTEi~ E  mist; the " atlas," e. g., has no power
OF THE CROCODILE.    of rotation upon the  "axis," in the
crocodile, and it is only in the upright skeleton of man that the large globular head is
sustained upon the shoulder-like processes of the " atlas."
In the crocodile, these vertebrae are concealed by the peculiarly prolonged angle of the lower jaw in the side view
of the skeleton (Fig. 18), and a figure of the two vertebra
is therefore subjoined (Fig. 19). The pleurapophyses, pl,
are retained in both segments, as in all the other vertebrae
of the trunk. That of the atlas, pl, a, is a simple slender
style, articulated by the head only, to the " hypapophysis,"
ahy. The neurapophyses, na, of the atlas retain their
primitive distinctness; each rests in part upon the proper
body of the atlas, ca, in part upon the hypapophysis. The
neural spine, ns, a, is also here an independent part, and
rests upon the upper extremities of the neurapophyses.
It is broad and flat, and prepares us for the further metamorphosis of the corresponding element in the cranial
vertebrae.
The centrum of the atlas, ca, called the " odontoid process of the axis" in human anatomy, here supports the
abnormallv-advanced rib of the axis vertebra, pl, x. The
proper centrum of the axis vertebra, cx, is the only one




VERTEBRA] OF THE CItOCODILE.              97
in the cervical series which does not support a rib; it
articulates by suture with its neurapophyses nx, and is
characterized by having its anterior surface flat, and its
posterior one convex.
With the exception of the two sacral vertebrae, the
bodies of which have one articular surface flat and the
other concave, and of the first caudal vertebra, the body
of which has both articular surfaces convex, the bodies of
all the vertebrae beyond the axis have the anterior articular
surface concave, and the posterior one convex, and articulate with one another by ball-and-socket joints. This
type of vertebra, which I have termed "procoelian" (ipom,
before, xoLXos, concave), characterizes all the existing genera
and species of the order Crocodilia with all the extinct
species of the tertiary periocls, and also two extinct species
of the greensand formation in New Jersey.' Here, so
far as our present knowledge extends, the type was lost,
and other dispositions of the articular surfaces of the
centrum  occur in the vertebra of the crocodilia of the
older secondary formations. The only known crocodilian
genus of the periods antecedent to the chalk and greensand deposits with vertebra articulated together by balland-socket joints, have the position-of the cup and the
ball the reverse of that in the modern crocodiles; and one
genus, thus characterized by vertebrae of the "opisthocCelian" type (oiatto,5 behind, xo5os, concave), has accordingly been termed streptospondylus, signifying " vertebrae
reversed."  But the most prevalent type of vertebra
amongst the crocodilia of the secondary periods was that
in which both articular surfaces of the centrum were concave, but in a less degree than in the single concave sur"Quarterly Journal of the Geological Society," November, 1849.
9




98        VERTEBRtE OF THE CROCODILE.
face of the vertebrae united by ball and socket. Vertebrse
of this "amphiccelian" type (auts, both, xos&o;, concave)
existed in the teleosaurus and steneosaurus. In the ichthyosaurus, the concave surfaces are usually deepened to
the extent and in the form shown in those of the fish
(Cut 8). Some of the most gigantic of the crocodilia of
the secondary strata had one end of the vertebral centrum
flattened, and the other (hinder) end concave; this "platycoelian" type (c&a-v;, flat, xocXo;, concave) we find in the
dorsal and caudal vertebrae of the gigantic cetiosaurus.
With a few exceptions, all the modern reptiles of the
order lacertilia have the same proccelian type of vertebrae
as the modern crocodilia, and the same structure prevailed as far back as the period of the mosasaurus, and
in some smaller members of the lacertilian order in the
cretaceous and wealden epochs.
Resuming the special description of the osteology of the
modern crocodilia, we find the proccelian type of centrum
established in the third cervical, which is shorter but
broader than the second; a parapophysis is developed
from the side of the centrum, and a diapophysis from the
base of the neural arch; the pleurapophysis is shorter, its
fixed extremity is bifid, articulating to the two abovenamed processes; its free extremity expands, and its anterior angle is directed forwards to abut against the inner
surface of the extremity of the rib of both the axis and
atlas, whilst its posterior prolongation overlaps the rib of
the fourth vertebra. The same general characters and
imbricated coadaptation of the ribs (Fig. 18), pl, characterize the succeeding cervical vertebrae to the seventh
inclusive, the hypapophysis progressively though slightly
increasing in size. In the eighth cervical the rib becomes
elongated, and slender; the anterior angle is almost or




VERTEBRAE OF THE CROCODILE.             99
quite suppressed, and the posterior one more developed
and produced more downwards, so as to form the body of
the rib, which terminates, however, in a free point. In
the ninth cervical, the rib is increased in length, but is
still what would be termed a "false" or "floating rib" in
anthropotomy.
In the succeeding vertebra the pleurapophysis articulates
with a habmapophysis, and the haemal arch is completed
by a hemal spine; and by this completion of the typical
segment we distinguish the commencement of the series
of dorsal vertebrae (ib.), D. With regard to the so-called
"perforation of the transverse process" this equally exists
in the present vertebra, as in the cervicals; on the other
hand, the cervical vertebrae equally show surfaces for the
articulation of ribs. The typical characters of the segment, due to the completion of both neural and haemal
arches, are continued in some species of crocodilia to the
sixteenth, in some (crocodilus acutus) to the eighteenth
vertebra. In the crocodilus aculus and the alligator lucius
the hemapophysis of the eighth dorsal rib (seventeenth
segment from the head) joins that of the antecedent vertebra. The pleurapophyses project freely outwards, and
become " floating ribs" in the eighteenth, nineteenth, and
twentieth vertebrae, in which they become rapidly shorter,
and in the last appear as mere appendages to the end of
the long and broad diapophyses: but the hbemapophyses
by no means disappear after the solution of their union
with their pleurapophyses; they are essentially independent elements of the segment, and they are continued,
therefore, in pairs along the ventral surface of the abdomen of the crocodilia, as far as their modified homotypes
the pubic bones. They are more or less ossified, and are
generally divided into two or three pieces.




100      VERTEBRAE OF TIIE CROCODILE.
The lumbar vertebrae are those in which the diapophyses cease to support the movable pleurapophyses, although
they are elongated by the coalesced rudiments of such
which are distinct in the young crocodilia. The length
and persistent individuality of more or fewer of these
rudimental ribs determines the number of the dorsal and
lumbar vertebrae respectively, and exemplifies the purely
artificial character of the distinction.  The number of
vertebra or segments between the skull and the sacrum,
in all the crocodilia I have yet examined, is twenty-four.
In the skeleton of a gavial, I have seen thirteen dorsal
and two lumbar; in that of a crocodilus cataphractus,
twelve dorsal and three lumbar; in those of-a crocodilus
acutus and alligator lucius, eleven dorsal and four lumbar,
and this is the most common number; but in the skeleton
of the crocodile, probably the species called croc. biporcatus, described by Cuvier, he gives five as the number
of the lumbar vertebrae. But these varieties in the development or coalescence of the stunted pleurapophysis
are of little essential moment; and only serve to show
the artificial character of the "'dorsal" and "lumbar"
vertebrae. The coalescence of the rib with the diapophysis obliterates of course the character of the "costal
articular surfaces," which we have seen to be common to
both dorsal and cervical vertebre.  The lumbar zygapophyses have their articular surfaces almost horizontal,
and the diapophyses, if not longer, have their anteroposterior extent somewhat increased; they are much depressed, or flattened horizontally.
The sacral -vertebre are very distinctly marked by the
flatness of the coadapted ends of their centrums; there
are never more than two such vertebrae in the crocodilia
recent or extinct: in the first, the anterior surface of the




VERTEBRYE OF THE CROCODILE.             101
centrum is concave; in the second, it is the posterior surface; the zygapophyses are not obliterated in either of
these sacral vertebrae, so that the aspects of their articular
surface-upwards in the anterior pair, downwards in the
posterior pair-determines at once the corresponding extremity of a detached sacral vertebra. The thick and
strong transverse processes form another characteristic of
these vertebrae; for a long period the suture near their
base remains to show how large a proportion is formed
by the pleurapophysis. This element articulates more
with the centrum than with the diapophysis developed
from the neural arch; it terminates by a rough, truncate,
expanded extremity, which almost or quite joins that of
the similarly but more expanded rib of the other sacral
vertebrae. Against these extremities is applied a supplementary costal piece, serially homologous with the
appendage to the proper pleurapophysis in the dorsal
vertebrae, but here interposing itself between the pleurapophyses and hbemapophyses of both sacral vertebrae,
not of one only. This intermediate pleurapophysial
appendage is called the "ilium;" it is short, thick,
very broad, and subtriangular, the lower truncated apex
forming with the connected extremities of the haemapophysis an articular cavity for the diverging appendage,
called the "hind leg."  The heminapophysis of the anterior sacral vertebra is called "pubis," 64; it is moderately long and slender, but expanded and flattened at
its lower extremity, which is directed forwards towards
that of its fellow, and joined to it through the intermedium of a broad, cartilaginous, haemal spine, completing the haemal canal. The posterior haemopophysis,
63, is broader, subdepressed, and subtriangular, expanding as it approaches its fellow to complete the second
9*




102      VERTEBRA, OF THE CROCODILE.
haemal arch; it is termed " ischium." The great development of all the elements of these haemal arches, and the
peculiar and distinctive forms of those that have thereby
acquired, from the earliest dawn of anatomical science,
special names, relates physiologically to the functions of
the diverging appendage which is developed into a potent
locomotive member. This limb appertains properly, as
the proportion contributed by the ischium to the articular
socket and the greater breadth of the pleurapophysis show,
to the second sacral vertebra; to which the ilium chiefly
belongs.
The first caudal vertebra, which presents a ball for
articulating with a cup on the back part of the last sacral,
retains, nevertheless, the typical position of the ball on
the back part of the centrum; it is thus biconvex, and
the only vertebra of the series which presents that
structure.
The first caudal vertebra, moreover, is distinguished
from the rest by having no articular surfaces for the hsemapophyses, which in the succeeding caudals form  a
hkemal arch, like the neurapophyses above, by articulating directly with the centrum. The arch so formed has
its base not applied over the middle of a single centrum,
but, like the neural arch in the back of the tortoise and
sacrum of the bird, across the interspace between two
centrums. The first hoemal arch of the tail belongs, however, to the second caudal vertebra, but it is displaced a
little backwards from its typical position.
The caudal hoemapophyses, hh, coalesce at their lower
or distal ends, from which a spinous process is prolonged
downwards and backwards; this grows shorter towards
the end of the tail, but is compressed and somewhat expanded antero-posteriorly. The hbemal arch so constituted
has received the name of "chevron bone."




VERTEBRAJ OF THE CROCODILE.              103
It is very true, as Cuvier said in the last lecture he delivered, "if we were agreed as to the crocodile's head, we
should be so as to that of other animals; because the
crocodile is intermediate between mammals, birds, and
fishes." Accordingly, the following description of the
crocodile's skull is coextensive with that of the fish; if
the answerable bones are rightly determined between
these, their correspondence with those of other vertebrates will be facilitated. The difficulties in comprehending the nature of some of the bones of the crocodile's
head have arisen through passing to its comparison from
that of the mammal's skull —by descending instead of
ascending to it.
The segments composing the skull are more modified
than those of the pelvis; but just as the vertebral pattern
is best preserved in the neural arches of the pelvis, which
are called collectively "sacrum," so, also, is it in the same
arches of the skull, which are called collectively "cranium." The elements of which these cranial arches are
composed, preserve, moreover, their primitive or normal
individuality more completely than in any of the vertebra
of the trunk, except the atlas, and consequently the archetypal character can be more completely demonstrated.'
If, after separating the atlas from the occiput, we proceed to detach the occipital segment of the cranium from
the next segment in advance, we find the detached segment presenting the form and structure of the neural arch.
The " centrum" presents, like those of the trunk, a convexity or ball at its posterior articular surface, but its
anterior one, like the hindmost centrum of the sacrum,
I The skull of the crocodile, partially disarticulated, and with the
bones numbered as in the following description, may be had of Mr.
Flower, No. 22 Lambeth Terrace, Lambeth Road.




104        SKULL OF THE CROCODILE.
unites with the next centrum in advance by a flat rough
" sutural" surface. Like most of the centrums in the neck
and beginning of the back, that of the occiput develops
a hypapophysis, but this descending process is longer
and larger, its base extending over the whole of the under
surface of the centrum. It is a character whereby the
occipital centrum of a crocodilian reptile may be distinguished from that of a lacertian one; for in the latter
a pair of diverging hypapophyses project from the under
surface, as is shown in most recent lizards and in the
great extinct mosasaurus.
The upper and lateral parts of No. 1 present rough
sutural surfaces, like those in the centrums of the trunk,
for articulating with the " neurapophyses," Nos. 2, 2,
which develop short, thick, obtuse, transverse processes,
4, 4. The modified or specialized character of the elements of the cranial vertebrae has gained for.them special
names. The centrum, 1, is called, as in fishes and all
other vertebrates, the "basioccipital;" the neurapophyses, 2, 2, are the "exoccipitals;" the neural spine, 3, is
the "superoccipital."  The transverse processes, 4, 4,
which may combine both diapophyses and paropophyses,
are called the "paroccipitals;" they are never detached
bones in the crocodilia, as they are in the chelonia and
in most fishes. The exoccipitals perform the usual functions of neurapophyses, and, like those of the atlas, meet
above the neural canal; they are perforated to give exit
to the vagal and hypoglossal nerves, and protect the
sides of the medulla oblongata and cerebellum-the two
divisions of the epencephalon. The superoccipital, 3, is
broad and flat, like the similarly detached neural spine
of the atlas; it advances a little forwards, beyond its sustaining neurapophyses, to protect the upper surface of




SKULL OF THE CROCODILE.               105
the cerebellum; it is traversed by tympanic air-cells, and
assists with the exoccipitals, 2, 2, in the formation of the
chamber for the internal ear.
The chief modification of the occipital segment of the
skull, as compared with that of the osseous fish, or with
the typical vertebra, is the absence of an attached haemal
arch. We shall afterwards see that this arch is present
in the crocodile, although displaced backwards.
Proceeding with the neural arches of the crocodile's
skull, if we dislocate the segment in advance of the occiput, we bring away, in connection with the long basebone, 5, the bone, 9, which in the figure of the section of
the serpent's skull (Cut 17) is shown similarly united to
5. In fact, the centrums of.the vertebrae have here coalesced, as we find to happen. in the neck of the siluroid
fishes, and in the sacrum of birds and mammals. The
two connate cranial centrums must be artificially divided,
in order to obtain the segments distinct to which they
belong. The hinder portion, 5, of the great base-bone,
which is the centrum of the parietal vertebra, is called
" basisphenoid." It supports that part of the " mesencephalon," which is formed by the lobe of the third ventricle, and its upper surface is excavated for the pituitary
prolongation of that cavity. The basisphenoid develops
from its under surface a "hypapophysis," which is suturally united with the fore part of that of the basioccipital,
but extends further down, and is similarly united in
front to the " pterygoids," 24. These rough sutural surfaces of the long descending process of the basisphenoid
are very characteristic of that centrum, when detached,
in a fossil state. The neurapophyses of the parietal vertebra, 6, 6, or the ", alisphenoids," protect the sides of the
mesencephalon, and are notched at their anterior margin,




106         SKULL OF THE CROCODILE.
for a conjugational foramen transmitting the trigeminal
nerve. As accessory functions they contribute, like the
corresponding bones in fishes, to the formation of the
ear-chamber. They have, however, a little retrograded
in position, resting below in part upon the occipital centrum, and supporting more of the spine of that segment,
3, than of their own, 7. The spine of the parietal vertebra is a permanently distinct, single, depressed bone, like
that of the occipital vertebra; it is called the "parietal,"
and completes the neural arch, as its crown or key-bone;
it is partially excavated by the tympanic air-cells, and
overlaps the superoccipital. The bones, 8, 8, wedged
between 6 and 7, manifest more of their diapophysial
character than their homotypes, 4, 4, do in the occipital
segment, since they support modified ribs, are developed
from independent centres, and preserve their individuality.'They form no part of the inner walls of the cranium, but send outwards and backwards a strong transverse process for muscular attachment. They afford a
ligamentous attachment to the haemal arch of their own
segment, and articulate largely with the pleurapophyses,
28, of the antecedent haemal arch, whose more backward
displacement, in comparison with its position in the fish's
skull, is well illustrated in the mntamorphosis of the toad
and frog.
On removing the neural arch of the parietal vertebra,
after the section of its confluent centrum, the elements
of the corresponding arch of the frontal vertebra present
the same arrangement. The compressed produced centrum has its form modified like that of the vertebral centrums at the opposite extreme of the body in many
birds; it is called the " presphenoid." The neurapophyses, 10, 10, articulate with the upper part of 9; they are




SKULL OF THE CROCODILE.              107
expanded, and smoothly excavated on their inner surface
to support the sides of the large prosencephalon; they
dismiss the great optic nerves by a notch. They show
the same tendency to a retrograde change of position as
the neighboring neurapophyses, 6; for though they support a greater proportion of their proper spine, 11, they
also support part of the parietal spine, 7, and rest, in
part, below upon the parietal centrum, 5: the neurapophyses, 10, 10, are called "orbitosphenoids."  The neural
spine, 11, of the frontal vertebra retains its normal character as a single symmetrical bone, like the parietal
spine which it partly overlaps; it also completes the
neural arch of its own segment, but is remarkably extended longitudinally forwards, where it is much thickened, and assists in forming the cavities for the eyeballs;
it is called the " frontal" bone.
In contemplating in the skull itself, or such side view
as is given in Fig. 9, p. 22, of my work on the Archetype
Skeleton, the relative position of the frontal, 11, to the
parietal, 7, and of this to the superoccipital, 3, which is
overlapped by the parietal, just as itself overlaps the flattened spine of the atlas, we gain a conviction which cannot be shaken by any difference in their mode of ossification, by their median bipartition, or by their extreme
expansion in other animals, that the above-named single,
median, imbricated bones, each completing its neural
arch, and permanently distinct from the piers of such
arch, must repeat the same element in those successive
arches-in other words, must be "homotypes," or serially homologous. In like manner the serial homology
of those piers, called " neurapophyses," viz: the laminae
of the atlas, the exoccipitals, the alisphenoids, and the
orbitosphenoids, is equally unmistakable. Nor can we




108         SKULL OF TI-IE CROCODILE.
shut out of view the same serial relationship of the
paroccipitals, as coalesced diapophyses of the occipital
vertebra, with the mastoids 8, and the postfrontals, 12,
as permanently detached diapophyses of their respective
vertebra. All stand out from the sides of the cranium,
as transverse processes for muscular attachment; all are
alike autogenous in the turtles; and all of them, in fishes,
offer articular surfaces for the ribs or hremal*arches of
their respective vertebre; and these characters are retained in the postfrontals as well as in the mastoids of
the crocodiles.
The frontal diapophysis, 12, is wedged between the
back part of the spine, 11, and the neurapophysis, 10;
its outwardly projecting process extends also backwards,
and joins that of the succeeding diapophysis, 8; but, notwithstanding the retrogradation of the inferior arch, it
still articulates with part of its own pleurapophysial
element, 28, which forms the proximal element of that
arch.
There finally remain in the cranium of the crocodile,
after the successive detachment of the foregoing arches,
the bones terminating the forepart of the skull; but, notwithstanding the extreme degree of modification to which
their extreme position subjects them, we can still trace
in their arrangement a correspondence with the vertebrate
type.
A long and slender symmetrical grooved bone, 13,
between 24 and 24, like the ossified inferior half of the
capsule of the notochord, is continued forwards from the
inferior part of the centrum, 9, of the frontal vertebra, and
stands in the relation of a centrum to the vertical plates
of bone, 14, which expand as they rise into a broad, thick,
triangular plate, with an exposed horizontal superior sur



SKULL OF THE CROCODILE.              109
face. These bones, which are called "prefontals," stand
in the relation of " neurapophyses" to the rhinencephalic
prolongations of the brain commonly but erroneously
called "olfactory nerves;" and they form the piers or
haunches of a neural arch, which is completed above by
a pair of symmetrical bones, 15, called " nasals," which I
regard as a divided or bifid neural spine.
The centrum of this arch is established by ossification
in the expanded anterior prolongation of the fibrous capsule of the notochord, beyond the termination of its gelatinous axis. The median portion above specified retains
most of the formal characters of the centrum; but there
is a pair of long, slender, symmetrical ossicles, which,
from the seat of their original development, and their
relative position to the neural arch, must be regarded as
also parts of its centrum. And this ossification of the
element in question from different centres will be no new
or strange character to those who recollect that the vertebral body in man and mammalia is developed from three
centres. The term'"vomer" is applied to the pair of
bones, 13, because their special homology with the single
median bone, so called in fishes and mammals, is indisputable; but a portion of the same element of the skull
retains its single symmetrical character in the crocodile,
and is connate with the enormous pterygoids, 24, between
which it is wedged. In some alligators (all. niger) the
divided anterior vomer extends far forwards, expands
anteriorly, and appears upon the bony palate.
Almost all the other bones of the head of the crocodile
are adjusted so as to constitute four inverted arches.
These are the haemal arches of the four segments or vertebrae, of which the neural arches have been just described.
But they have been the seat of much greater modifica10




110        SKULL OF TIIE CROCODILE.
tions, by which they are made subservient to a variety of
functions unknown in the haemal arches of the rest of the
body. Thus, the two anterior hbemal arches of the head
perform the office of seizing and bruising the food; are
armed for that purpose with teeth: and, whilst one arch
is firmly fixed, the other works upon it like the hammer
upon the anvil. The elements of the fixed arch, called
"maxillary arch," have accordingly undergone the greatest amount of morphological change, in order to adapt
that arch to its share in mastication, as well as for forming
part of the passage for the' respiratory medium, which is
perpetually traversing this hbemal canal in its way to
purify the blood. Almost the whole of the upper surface
of the maxillary arch is firmly united to contiguous parts
of the skull by rough or sutural surfaces, and its strength
is increased by bony appendages, which diverge from it
to abut against other parts of the skull. Comparative
anatomy teaches that, of the numerous places of attachment, the one which connects the maxillary arch by its
element, 20, with the centrum, 13, and the descending
plates of the neurapophyses, 14, of the nasal segment, is
the normal or the most constant point of its suspension,
the bone, 20, being the pleurapophysial element of the
maxillary arch: it is called the "palatine," because the
under surface forms a portion of the bony roof of the
mouth, called the "palate." It is articulated at its fore
part with the bone, 21, in the same plates, which bone is
the hsemapophysial element of the maxillary arch: it is
called the "maxillary," and is greatly developed both in
length and breadth; it is connected not only with 20 behind, and 22 in front, which are parts of the same arch,
and with the diverging appendages of the arch, viz., 26,
the malar bone, and 24, the pterygoid, but also with the




SKULL OF THE CROCOIDILE.             111
nasals, 15, and the lachrymal, 16, as well as with its fellow
of the opposite side of the arch. The smooth, expanded
horizontal plate, which effects the latter junction, is called
the palatal plate of the maxillary; the thickened external
border, where this plate meets the external rough surface
of the bone, and which is perforated for the lodgment of
the teeth, is the "alveolar border" or "process" of the
maxillary. The huemal spine or key-bone of the arch, 22,
is bifid, and the arch is completed by the symphysial
junction of the two symmetrical halves; these halves are
called "premaxillary bones:" these bones, like the maxillaries, have a rough facial plate, and a smooth palatal
plate, with the connecting alveolar border. The median
symphysis is perforated vertically through both plates;
the outer or upper hole being the external nostril, the
under or palatal one being the prepalatal or naso-palatal
aperture.
Both the palatine and the maxillary bones send outwards
and backwards parts or processes which diverge from the
line of the hsemal arch, of which they are the chief elements; and these parts give attachment to distinct bones
which form the ",diverging appendages" of the arch, andl
serve to attach it, as do the diverging appendages of the
thoracic hbemal arches in the bird, to the succeeding arch.
The appendage 24, called "pterygoid," effects a more
extensive attachment, and is peculiarly developed in the
crocodilia. As it extends backwards it expands, unites
with its fellow below the nasal canal, and encompassing
that canal, coalesces above it with the vomer, and is firmly
attached by suture to the presphenoid and basisphenoid:
it surrounds the hinder or palatal nostril, and, extending
outwards, it gives attachment to a second bone, 25, called
" ectopterygoid," which is firmly connected with the max



112         SKULL OF THE CROCODILE.
illary, 25, the malar, 26, and the postfrontal, 12. The
second diverging ray is of great strength; it extends from
the maxillary, 21 ("haemapophysis" of the maxillary arch),
to the tympanic, 28 (" pleurapophyses" of the mandibular
arch), and is divided into two pieces, the malar, 26, and
the squamosal, 27. Such are the chief crocodilian modifications of the hoemal arch, and appendages of the anterior or nasal vertebra of the skull.
The hsemal arch of the frontal vertebra is somewhat less
metamorphosed, and has no diverging appendage. It is
slightly displaced backwards, and is articulated by only a
small proportion of its pleurapophysis, 28, to the parapophysis, 12, of its own segment; the major part of that
short and strong rib articulating with the parapophysis,
8, of the succeeding segment. The bone, 28, called "tympanic," because it serves to support the "drum of the ear"
in air-breathing vertebrates, is short, strong, and immovably wedged, in the crocodilia, between the paroccipital,
4, mastoid, 8, postfrontal, 12, and squamosal, 27; and the
conditions of this fixation of the pleurapophysis are exemplified in the great development of the hsemapophysis
(mandible), which is here unusually long, supports nurnerous teeth, and requires, therefore, a firm point of suspension, in the violent actions to which the jaws are put in
retaining and overcoming the struggles of a powerful
living prey. The movable articulation between the pleurapophysis, 28, and the rest of the hsemal arch is analogous
to that which we find between the thoracic pleurapophysis
and hbemapophysis in the ostrich and many other birds.
But the hiemopophysis of the mandibular arch in the
crocodiles is subdivided into several pieces, in order to
combine the greatest elasticity and strength with a not
excessive weight of bone. The different pieces of this




SKELETON OF THE CROCODILE.              1.13
purposely subdivided element have received  definite
names. That numbered 29, which offers the articular
concavity to the convex condyle of the tympanic, 28, is
called the"articular" piece; that beneath it, 30, which
develops the angle of the jaw, when this projects, is the
" angular" piece; the piece above, 29', is the " surangular;"
the thin, broad, flat piece, 31, applied, like a splint, to the
inner side of the other parts of the mandible, is the
"splenial;" the small accessory ossicle, 31', is the "coronoid," because it develops the process, so called, in lizards;
the anterior piece, 32, which supports the teeth, is called
the "dentary." This latter is the homotype of the premaxillary, or it represents that bone in the mandibular
arch, of which it may be regarded as the haemal spine;
the other pieces are subdivisions of the hemapophysial
element. The purport of this subdivision of the lower
jaw-bone has been well explained by Conybearel and
Buckland,2 by the analogy of its structure to that adopted
in binding together several parallel plates of elastic wood
or steel to make a crossbow, and also in setting together
thin plates of steel in the springs of carriages. Dr. Buckland adds: " Those who have witnessed the shock given
to the head of a crocodile by the act of snapping together
its thin long jaws, must have seen how liable to fracture
the lower jaw would be, were it composed of one bone only
on each side." The same reasoning applies to the composite structure of the long tympanic pedicle in fishes.
In each case the splicing and bracing together of thin flat
bones of unequal length and of varying thickness, affords
compensation for the weakness and risk of fracture that
"Geol. Trans.," 1821, p. 565,
"13Bridgewater Treatise," 1836, vol. i. p. 176.
1 0 -%




114       SKELETON OF THE CROCODILE.
would otherwise have attended the elongation of the parts.
In the abdomen of the crocodile, the analogous subdivision
of the hbemapophyses, there called abdominal ribs, allows
of a slight change of their length, in the expansion and
contraction of the walls of that cavity; and since amphibious reptiles, when on land, rest the whole weight of the
abdomen directly upon the ground, the necessity of the
modification for diminished liability to fracture further
appears. These analogies are important, as demonstrating
that the general homology of the elements of a natural
segment of the skeleton is not affected or obscured by
their subdivision for a special end. Now this purposive
modification of the haemapophyses of the frontal vertebra,
is but a repetition of that which affects the same elements
in the abdominal vertebrae.
Passing next to the huemal arch of the parietal vertebra, we are first struck by its small relative size. Its
restricted functions have not required it to grow in proportion with the other arches, and it consequently retains
much of its embryonic dimensions. It consists of a
ligamentous" "stylohyal," its pleurapophysis retaining the
same primitive histological condition which obstructs the
ordinary recognition of the same elements of the lumbar
haemal arches. A cartilaginous "epihyal," 39, intervenes
between this and the ossified "hbemapophysis," 40, which
bears the special name of ceratohyal. The hbemal spine,
41, retains its cartilaginous state, like its homotypes, in
the abdomen; there they get the special name of "abdominal sternum," here of "basihyal."  The basihyal has,
however, coalesced with the thyrohyals to form a broad
cartilaginous plate, the anterior border rising like a valve
to close the fauces, and the posterior angles extending
beyond and sustaining the thyroid and other parts of the




LIMBS OF THE CROCODILE.              115
larynx. The long, bony "ceratohyal," and the commonly
cartilaginous " epihyal," are suspended by the ligamentous "stylohyal" to the paroccipital process; the whole
arch having, like the mandibular one, retrograded from
the connection it presents in fishes.
This retrogradation is still more considerable in the
succeeding haemal arch. In comparing the occipital segment of the crocodile's skeleton with that of the fish, the
chief modification that distinguishes that segment in the
crocodile is the apparent absence of its haemal arch. We
recognize, however, the special hornologues of the constituents of that arch of the fish's skeleton in the bones
51 and 52 of the crocodile's skeleton (Fig. 18); but the
upper or suprascapular piece, 50, retains, in connection
with the loss of its proximal or cranial articulations, its
cartilaginous state; the scapula, 51, is ossified, as is likewise the coracoid, 52, the lower end of which is separated
from its fellow by the interposition of a median, symmetrical, partially-ossified piece called "' episternum." The
power of recognizing the special homologies of 50, 51,
and 52 in the crocodile, with the similarly-numbered
constituents of the same arch in fishes —though masked,
not only by modifications of form and proportion, but
even of very substance, as in the case of 50-depends
upon the circumstance of these bones constituting the
same essential element of the archetypal skeleton, viz.,
the fourth huemal arch, numbered pl, 52, in Fig. 7: for
although in the present instance there is superadded, to
the adaptive modifications above cited, the rarer one of
altered connections, Cuvier does not hesitate to give the
same names, "suprascapulaire" to 50, and "scapulaire"
to 51, in both fish and crocodile; but he did not perceive
or admit that the narrower relations of special homology




lae        LIMBS OF THE CROCODILE.
were a result of, and necessarily included in, the wider
law of general homology. According to the latter law,
we discern in 50 and 51 a compound "pleurapophysis,"
in 52 a "hsemapophysis," and in hs, the "hbemal spine,"
completing the haemal arch.
The scapulo-coracoid arch, both elements, 51, 52, of
which retain the form of strong and thick vertebral and
sternal ribs in the crocodile, is applied in the skeleton of
that animal over the anterior thoracic haemal arches.
Viewed as a more robust hsemal arch, it is obviously out
of place in reference to the rest of its vertebral segment.
If we seek to determine that segment by the mode in
which we restore to their centrums the less displaced
neural arches of the antecedent vertebrae of the cranium
or in the sacrum of the bird,' we proceed to examine the
vertebrae before and behind the displaced arch, with the
view to discover the one which needs it, in order to be
made typically complete. Finding no centrum and neural arch without its pleurapophyses from the scapula to
the pelvis, we give up our search in that direction; and
in the opposite direction we find no vertebra without its
ribs, until we reach the occiput; there we have centrum
and neural arch, with coalesced parapophyses, but without the hsemal arch, which arch can only be supplied by
a restoration of the bones 50-52 to the place which they
naturally occupy in the skeleton of the fish. And since
anatomists are generally agreed to regard- the bones
50-52 in the crocodile (Fig. 18) as specially homologous
with those so numbered in the fish (Fig. 9), we must conclude that they are likewise homologous in a higher
I See "On the Archetype and Homologies of the Vertebrate Skeleton,"
pp. 117 and 159.




LIMBS OF THE CROCODILE.             117
sense; that in the fish the scapula-coracoid arch is in its
natural or typical position, whereas in the crocodile it
has been displaced for a special purpose. Thus, agreeably with a general principle, we perceive that, as the
lower vertebrate animal illustrates the closer adhesion to
the archetype by the natural articulation of the scapulocoracoid arch to the occiput, so the higher vertebrate
manifests the superior influence of the antagonizing
power of adaptive modification by the removal of that
arch from its proper segment.
The anthropotomist, by this mode of counting and defining the dorsal vertebrae and ribs, admits, unconsciously
perhaps, the important principle in general homology
which is here exemplified; and which, pursued to its
legitimate consequences, and further applied, demonstrates that the scapula is the modified rib of that
centrum and neural arch, which he calls the " occipital
bone;" and that the change of place which chiefly masks
that relation (for a very elementary acquaintance with
comparative anatomy shows how little mere form and
proportion affect the homological characters of bones),
differs only in extent, and not in kind, from the modification which makes a minor amount of comparative observation requisite, in order to determine the relation of the
shifted dorsal rib to its proper centrum in the human
skeleton.
With reference, therefore, to the occipital vertebra of
the crocodile, if the comparatively well-developed and
permanently-distinct ribs of all the cervical vertebrae
prove the scapular arch to belong to none of those segments, and if that haemal arch be required to complete
the occipital segment, which it actually does complete in




11(J     FORE-LIMB OF THIE CROCODILE.
fishes, then the same conclusion must apply to the same
arch in other animals, up to man himself.
The anterior locomotive extremity is the diverging appendage of the arch, under one of its numerous modes
and grades of development.  The proximal element of
this appendage, or that nearest the arch, is called the
"humerus," 53 (Fig; 18).  The second segment of the
limb consists of two bones; the larger one, 54, is called
the "ulna:" it articulates with the outer condyle of the
humerus by an oval facet, the thick convex border of
which swells a little out behind, and forms a kind of
rudimental " olecranon;" the distal end is much less than
the proximal one, and is most produced at the radial side.
The radius, 55, has an oval head; its shaft is cylindrical; its distal end oblong and subcompressed.
The small bones, 56, which intervene between these
and the row of five longer bones, are called " carpals;"
they are four in number in the crocodilia. One seems to
be a continuation of the radius, another of the ulna; these
two are the principal carpals; they are compressed in the
middle, and expanded at their two extremities: that on
the radial side of the wrist is the largest. A third small
ossicle projects slightly backwards from the proximal end
of the ulnar metacarpal; it answers to the bone "pisiforme" in the human wrist. The fourth ossicle is interposed between the ulnar carpal and the metacarpals of
the three ulnar digits.
These five terminal-jointed rays of the appendage are
counted from the radial to the ulnar side, and have received special names; the first is called "pollex," the
second "index," the third "medius," the fourth " annularis," and the fifth "minimus." The first joint of each
digit is called " metacarpal;" the others are termed "pha



PELVIS AND HIND-LIMIB OF THE CROCODILE. 119
lanx." In the crocodilia, the pollex has two phalanges,
the index three, the medius four, the annularis four, and
the minimus three. The terminal phalanges, which are
modified to support claws, are called " ungual" phalanges.
As the above-described bones of the scapular extremity
are developments of the appendage of the scapular arch,
which is the hsemal arch of the occipital vertebra, it
follows, that, like the branchiostegal rays and opercular
bones in fishes, they are essentially bones of the head.
But the enumeration of the bones of the crocodile's skull
is not completed by these; there is a bone anterior to the
orbit, which is perforated at its orbital border by the duct
of the lachrymal gland, whence it is termed the " lachrymal bone," and its facial part extends forwards between
the bones marked 14, 15, 21, and 26. In many crocodilia there is a bone at the upper border of the orbit,
which extends into the substance of the upper eyelid; it
is called "superorbital."  In the crocodilus palpebrosus
there are two of these ossicles.
Both the lachrymal and superorbital bones answer to a
series of bones found commonly in fishes, and called
" suborbitals" and " superorbitals."  The lachrymal is the
most anterior of the suborbital series, and is the largest
in fishes; it is also the most constant in the vertebrate
series, and is grooved or perforated by a mucous duct.
These ossicles appertain to the dermal or muco-dermal
system or "exoskeleton," not to the vertebral system or
" endoskeleton."
There remains, to complete this sketch of the osteology
of the crocodile, a brief notice of the bones composing
the diverging appendage of the pelvic arch: these being
a repetition of the same element as the appendage of the
scapular arch, modified and developed for a similar office,




120 PELVIS AND HIND-LIMB OF THE CROCODILE.
manifest a very close resemblance to it. The first bone,
called the "femur," is longer than the humerus, and, like
it, presents an enlargement of both extremities, with a
double curvature of the intervening shaft, but the directions are the reverse of those of the humerus, as may be
seen in Fig. 18, where the upper or proximal half of the
femur is concave, and the distal half convex, anteriorly.
The head of the femur is compressed from side to side,
not from before backwards, as in the humerus; a pyramidal protuberance from the inner surface of its upper
fourth represents a "trochanter;" the distal end is expanded transversely, and divided at its back part into two
condyles. The next segment of the hind-limb or "leg,"
includes, like the corresponding segment of the fore-limb
called "fore-arm," two bones. The largest of these is the
"tibia," 66, and answers to the radius. It presents a large,
triangular head to the femur; it terminates below by an
oblique crescent with a convex surface. The "fibula" is
much compressed above; its shaft is slender and cylindrical, its lower end is enlarged and triangular. The
group of small bones which succeed those of the leg are
the tarsals; they are four in number, and have each a
special name. The " astragalus" articulates with the tibia,
and supports the first and part of the second toe. The
calcaneum intervenes between the fibula and the ossicle
supporting the two outer toes; it has a short but strong
posterior tuberosity.  The ossicle referred to represents
the bone called " cuboid" in the human tarsus. A smaller
ossicle, wedged between the astragalus and the metatarsals of the second and third toes is the "ectocuneiform."
Four toes only are normally developed in the hind-foot
of the crocodilia; the fifth is represented by a stunted
rudiment of its metatarsal, which is articulated to the




PELVIS AND HIND-LIMB OF THE CROCODILE. 121
cuboid and to the base of the fourth metatarsal. The four
normal metatarsals are much longer than the corresponding metacarpals. That of the first or innermost toe is the
shortest and strongest; it supports two phalanges. The
other three metatarsals are of nearly equal length, but
progressively diminish in thickness from the second to
the fourth. The second metatarsal supports three phalanges; the third four; and the fourth also has four phalanges, but does not support a claw. The fifth digit is
represented by a rudiment of its metatarsal in the form of
a flattened triangular plate of bone, attached to the outer
side of the cuboid, and slightly curved at its pointed and
prominent end.
The forms and proportions of the entire skeleton of the
crocodile are adapted to the necessities of an amphibious
animal, but minister to much more rapid and energetic
movements in water than on land. The short limbs preclude the possibility of very quick course along shore;
and the overlapping of the ribs of the neck, whilst enabling the head the better to cleave the water during the
acts of diving or swimming, makes the bending of that
part from side to side an act of difficulty and time; this,
it is said, may avail any one pursued by a crocodile on
dry land to escape by turning out of the straight course.
But the crocodile usually seizes his prey by stratagem or
concealment when in or close to the water; and it is there
that he shows himself master of his position, and chiefly
by the powerful strokes of his long, large, verticallyflattened tail.
11




122   OSTEOLOGY OF CHELONIAN REPTILES.
OSTEOLOGY OF CHELONTAN REPTILESTORTOISES AND TURTLES.
Those animals to which, in the manifold modifications
of the organic framework, a portable dwelling or place
of refuge has been given, in compensation for inferior
powers of lomocotion or other means of escape or defence,
have always attracted especial attention; and of them the
most remarkable, both for the complex construction of
their abode as well as for their comparatively high organization, are the reptiles of the chelonian order. The
expanded thoracic-abdorninal case, into which, in most
chelonians, the head, the tail, and the four extremities
can be withdrawn, and in some of the species be there
shut up by movable doors closely fitting both the anterior and posterior apertures, as e.g. in the box-tortoises
(cinosternon, cistudo), has been the subject of many. and
excellent investigations; and not the least interesting
result has been the discovery that this seemingly special
and anomalous superaddition to the ordinary vertebrate
structure is due, in a great degree, to the modification of
form and size, and, in a less degree, to a change of relative
position, of ordinary elements of the vertebrate skeleton.
The natural dwelling-chamber of the chelonia consists
chiefly, and in the marine species (chelone) and mud-turtles
(trionyx) solely, of the floor and the roof; side-walls of
variable extent are added in the fresh-water species (emydians) and land-tortoises (testudinians). The whole consists
chiefly of osseous "plates" with superincumbent horny
plates or "scutes," except in the soft or mud-tortoises
(trionyx and sphargis), in which these latter are wanting.
Fig. 20 shows the manner in which the head and tail




OSTEOLOGY OF CHELONIAN REPTILES.  123
can be retracted within the thoracic-abdominal box; the
four limbs are figured as extended in the act of walking,
to show their structure. The only movable vertebrae are
those of the neck and tail, and the former enjoy a great
degree of flexibility. The vertebrae answering to the dorsal, lumbar, and sacral series are firmly fixed together;
but the dorsal ones, 1 to 8, are chiefly concerned in the
formation of the osseous dwelling-chamber. The composition of this will be first described as it exists in the
turtle (chelone), the species called "loggerhead" being here
selected for its illustration.
In the marine species of the chelonian order, of which
Fig. 20.
67
rv E                                               V ivl
SKELETON OF THE EUROPEAN TORTOISE.
this may be regarded as the type, the ossification of the
carapace and plastron is less extensive, and the whole
skeleton is lighter than in the box-tortoise (Fig. 20),
or any of those species that live on dry land.  The
head is proportionally larger —-a character common to




124         CARAPACE OF TtHE TURTLE.
aquatic animals; and, being incapable of retraction
within the carapace, ossification extends in the direction of the fascia covering the temporal muscles, and
forms a second bony covering of the cranial cavity; this
accessory defence is not due to the intercalation of any
new bones, but to exogenous growths from the frontals,
11, postfrontals, 12, parietals, 7, and mastoids, 8.
The carapace (Fig. 21) is composed of a series of median
and symmetrical pieces ch, s l to s 11, and of two series
of unsymmetrical pieces on each sided. The median pieces
have been regarded as lateral expansions of the summits
of the neural spines; the medio-lateral pieces as similar
developments of the ribs; and the marginal pieces as the
homologues of the sternal ribs. But the development
of the carapace shows that ossification begins independFig. 21.
CARAPACE OF TURTLE (Chelone imbricata).
ently in a fibro-cartilaginous matrix of the corium in the
first, ch, and some of the last, s9 to s11, median plates,




CARAPACE OF THE TURTLE.              125
and extends from the summnrits of the neural spines into
only eight of the intervening plates, s 1 to s 8; ossification
also extends into the contiguous lateral plates, pll to p18,
in some chelonia, not from the corresponding part of the
subjacent ribs, but from points alternately nearer and
further from their heads, showing that such extension of
ossification into the coriumn is not a development of the
tubercle of the rib, as has been supposed. Ossification
commences independently in the corium in all the marginal plates, in 1 to py, which never coalesce with the bones
uniting the sternum with the vertebral ribs, and which
are often more numerous, and sometimes less numerous
than those ribs, and in a few species are wanting.
Whence it is to be inferred that the expanded bones of
the carapace, which are supported and impressed by the
thick epidermal scutes called "tortoise-shell," are dermal
ossifications, homologous with those which support the
nuchal and dorsal epidermal scutes in the crocodile.
Most of the pieces of the carapace being directly continuous or connate with the obvious elements of the vertebrse, which have been supposed exclusively to form
them by their unusual expansion, the median ones, s  to
s811, have been-called "neural plates," and the mediolateral pieces, plI to p 8, " costal-plates;" but the external lateral pieces, mn 1 to in 12, have retained the name of
"marginal plates."  The first or anterior of the median
plates (ch, "nuchal plate") is remarkable for its great
breadth in the turtles, and usually sends down a ridge
from the middle line of its under surface, which articulates more or less directly with the summit of the neural
arch of the first dorsal vertebra; the second neural plate
is much narrower, and is connate with the summit of the
neural spine of the second dorsal vertebra; the seven suc11*




126         PLASTRON OF THE TURTLE.
ceeding neural plates have the same relations with the
succeeding neural spines; the rest are independent dermal bones. The costal plates of the carapace are superadditions to eight pairs of the pleurapophyses or vertebral portions of the second to the ninth ribs inclusive.
The slender or proper portions of these ribs project
freely for some distance beyond the connate dermal
portions, along the under surface of which the rib may
be traced, of its ordinary breadth to near the head, which
liberates itself from the costal plate to articulate to the
interspace of the two contiguous vertebrae, to the posterior of which such rib properly belongs.
The plastron, or floor of the bony house, consists in
the genus Chelone, as in the rest of the order, of nine
Fig. 22.
XI
PLASTRON OF CHELONE CAOUANNA.
pieces-one median and symmetrical, and the rest in
pairs. With regard to the homology of these bones,




VERTEBRAE OF THE TORTOISE.           1]27
three explanations may be given: one in conformity
with the structure of the thoracic-abdominal cage in the
crocodile; the other based upon the analogy of that part
in the bird; and the third agreeably with the phenomena
of development. According to the first, the median
piece of the plastron, called " entosternal," S, answers to
the sternum of the crocodile, or "sternum proper," and
the four pairs of plastron-pieces, es, hs, ps, xs, answer to
the "heemapophyses" forming the so-called sternal and
abdominal ribs of the crocodile. Most comparative anatomists have, however, adopted the views of Geoffroy St.
Hilaire, who was guided in his determination of the
pieces of the plastron by the analogy of the skeleton of
the bird; according to which all the parts of the plastron are referred to a complex and greatly developed
sternum, and the marginal plates are viewed as sternal
ribs (haemapophyses). The third ground of determina.
tion refers the parts of the plastron, like those of the
carapace, to a combination of parts of the endoskeleton
with those of the exoskeleton.
In Fig. 21, the marginal plates m 1 to m 12, are
twenty-four in number, or twenty-six if the first (nuchal,
ch) and last (pygal, py) vertebral plates be included.
Omitting these in the enumeration, three marginal pieces
intervene on each side at the angles between the first
median plate and the point of' the first costal plate formed
by the end of the second dorsal rib, which point enters a
depression in the fourth marginal piece, m 4; the fifth,
sixth, seventh, eighth, ninth, and tenth marginal plates
are similarly articulated by gomphosis to the six succeeding ribs; the eleventh marginal plate has no corresponding rib; the twelfth is articulated with the point of
the ninth dorsal rib supporting the eighth costal plate.




128       VERTEBRJE OF THE TORTOISE.
The want of concordance with the vertebral ribs, or
"pleurapophyses," arising from  the increased number of
the marginal pieces, favors the idea of their being dermal
ossifications, such peripheral elements being more subject to vegetative division and multiplication than the
hmemapophyses: the absence of the marginal pieces in
the trionyx gives additional support to the same view.
The median piece, S, is here regarded as a haemal spine:
it is called "entosternum."  The parial pieces of the plasFig. 23.
SEGMENT OF CARAPACE AND PLASTRON.
tron are the " hemapophyses" connate with expanded
dermal ossifications, and have received the following special names: es, "episternal;" hs, " hyosternal;" ps, "hyposternal;" xs, "xiphisternal."
In some extinct chelonia, the number of these lateral
elements of the plastron is increased by an intercalated
pair which I have called "mesosternals."  In the figure
of the segment, as modified to form the carapace and
plastron (Cut 23), the nature of the bones is indicated by
the letters according to the explanation given of the
archetype vertebrae (Fig. 5, p. 29), the dermal superadditions being marked sc.




VERTEBRAYS OF THE TORTOISE.            129
In the figure of the skeleton of the box-tortoise (Fig.
20) a section of the carapace and plastron has been removed from the right side to expose the dorsal and
sacral vertebrae, and the disposition of the scapular and
pelvic arches.  The eight cervical vertebrae are free,
movable, and ribless; the fourth of these vertebrae has
a much elongated centrum, which is convex at both
ends; the eighth is short and broad, with the anterior
surface of the body divided into two transversely elongated convexities, and the posterior part of the body
forming a single convex surface divided into two lateral
facets; the under part of the centrum is carinate. The
neural arch, which is anchylosed to this centrum, is
short, broad, obtuse, and overarched by the broad expanded nuchal plate, ch. The first dorsal vertebra, d 1,
is also short and broad, with two short and thick pleurapophyses, articulated by one end to the expanded anterior part of the centrum, and united by suture at the
other end to the succeeding pair of ribs. The head of
each rib of the second pair is supported upon a strong
trihedral neck, and articulated to the interspace of the
first and second dorsal vertebrae: it is connate, at the
part corresponding to the tubercle, with the first broad
costal plate, which articulates by suture to the lateral
margin of the first neural plate, and to portions of the
nuchal and third neural plates: the connate rib, which is
almost lost in the substance of the costal plate, is continued with it to the anterior and outer part of the carapace, where it resumes its subeylindrical form, and articulates with the second and third marginal pieces of the
carapace. The neural arch of the second dorsal vertebra
is shifted forwards to the interspace between its own centrum and that of the first dorsal vertebra. A similar
disposition of the neural arch and spine, and of the ribs,




130       VERTEBRAE OF THE TORTQISE.
prevails in the third to the ninth dorsal vertebrae inclusive. The corresponding seven neural plates are connate
with the spines of those vertebrae, and form the major part
of the median pieces of the carapace; the corresponding
costal plates, anchyclosed to the ribs, form the mediolateral pieces; the ninth, tenth, and pygal plates, with the
marginal plates of the carapace, do not coalesce with any
parts of the endoskeleton. The bony floor of the great
abdominal box, or 4" plastron," is formed by the hoemapophyses and sternum eonnate with dermal osseous plates,
forming, as in the turtle, nine pieces, one median and symmetrical, answering to the proper sternum, and eight in
pairs: but they are more ossified, and the hyo and hyposternals unite suturally with the fourth, fifth, and sixth
marginal plates, forming the side-walls of the bony chamber. The junction between the hyo- and hyposternals
admits of somne yielding movement. The iliac bones, 62,
abut against the pleurapophyses of the tenth, eleventh,
and twelfth vertebrae, counting from the first dorsal vertebra. These three vertebrae form the sacrum: their pleurapophyses are unanchylosed, converge, and unite at their
distal extremities to form the articular surface for the
ilium. Beyond these the vertebrae, thirty-five in number,
are free, with short, straight, and thick pleurapophyses,
articulated to the sides of the anterior expanded portions
of the centrums. They diminish to mere tubercles in the
first caudal vertebra, and disappear in the remainder. The
neural arches of the caudal vertebrae are flat above, and
without spines.  The strong columnar scapula, 51, is
attached by ligament to the first costal plate, and, retaining its primitive rib-like form, it descends almost vertically
to the shoulder-joint, of which it forms, in common with
the coracoid, 52, the glenoid cavity. A strong subcylindrical process or continuation of the scapula, representing




SKULL OF THE TORTOISE.             131
the acromion, bends inwards to meet its fellow at the
middle line. The coracoid continues distinct from the
scapula, expands, and becomes flattened at its median
extremity, which does not meet its fellow or articulate
with the sternum. The iliac bones, 62, are vertical and
columnar, like the scapula, but are shorter and more compressed: they articulate, but do not coalesce, with the
pubis, 64, and ischium, 63. The acetabulum is formed
by contiguous parts of all the three bones. The pubis
arches inwards, and expands to join its fellow at the median symphysis and the ischium posteriorly. It sends
outwards and downwards a long, thick, obtuse process from
its anterior margin. The ischia, in like manner, expand
where they unite together to prolong the symphysis backwards.
In the skull, the parietal crista is continued into the
occipital one without being extended over the temporal
fossse, as in the turtle; the fascia covering the muscular
masses in these fosss undergoing no ossification. The
bony hoop for the membrana tympani is incomplete
behind, and the columelliform stapes passes through a
notch instead of a foramen to attain the tympanic membrane. The mastoid is excavated to form a tympanic aircell. In the Australian long-necked terrapene (hydraspis
iongicollis) the head is much depressed, the mastoids are
excavated by large tympanic cells, and prolonged backwards: the frontal is produced forwards as far as the anterior nostril, where it terminates in a point between the
two nasals, which are here distinct from the prefrontals.
The margins of the upper and lower jaws are trenchant:
the hypapophysis of the atlas has the form of a diminutive
wedge-bone, forming as usual the lower part of the articular cup for the occipital condyle: the rest of the body




132          SKULL OF THE TORTOISE.
Of the atlas, or "odontoid," has coalesced with its proper
neural arch, which develops two transverse and two long
posterior oblique processes, as in the chelys.
In the true or land tortoises the temporal depressions
are exposed, as in the box-tortoises and fresh-water terrapenes: the head is proportionally small, and can be
withdrawn beneath the protective roof of the carapace.
The skull is rounder and less depressed than in the terrapenes: the frontals enter into the formation of the orbital
border. The tympanic hoop is notched behind, but the
columellifobrm stapes passes through a small foramen. The
palatine processes of the maxillaries are on a plane much
below that of the continuation of the basis cranii, formed
bythe vomer and palatines. In most of the chelonia, the
nasal bone is connate with the prefrontal; and, in all, the
tympanic pedicle is firmly wedged between the broad
appendage of the maxillary arch, formed by the malar,
26, and squamosal, 27, in front, and the mastoid, 8, behind.
The broad-headed terrapene (podocnemys expansa) differs
from other fresh-water tortoises, and approaches the marine tortoises (turtles), by the vaulted bony roof arching
over the temporal depressions. This roof is chiefly formed
by the parietals, but differs from that in the turtles in
being completed laterally by a larger proportion of the
squamosal than of the postfrontal, which does not exceed
its relative size in other terrapenes. The present species
further differs from the marine turtles in the nonossification of the vomer, and the consequent absence of a septum
in the posterior nostrils; in the greater breadth of the
pterygoids, which send out a compressed rounded process
into the temporal depressions: the orbits also are much
smaller, and are bounded behind by orbital processes of
the postfrontal and malar bones: the mastoids and paroc



LIMBS OF THE TORTOISE AND TURTLE. 133
cipitals are more produced backwards, and the entire skull
is more depressed than in the turtles.
The ordinary position of the scapular extremity is a
state of extreme pronation, as shown in Fig. 20, with the
olecranon, or top of 54, thrown forwards and outwards,
and the radial side of the hand, or thumb, i, directed to
the ground. The humerus, 53, is strongly bent in a sigmoid form, with the anconal surface convex and directed
upwards and outwards: the two tuberosities at the proximal end are much developed and bent towards the palmar
aspect, bounding a deep and wide groove: that which
answers to the external tuberosity is the smallest, and by
the rotation of the humerus it becomes the most internal
in position. The proximal row of the carpus consists of
four bones-viz: a large scaphoides, a small lunare,
wedged into the interspace of the radius and ulna, a large
cuneiforme, and a small pisiforme. The second row consists of five distinct bones, corresponding with the five
digits; those supporting the fourth and fifth answering to
the os unciforme, the remaining three to the trapezium,
trapezoides, and magnum. The first and fifth of the digits
have each one metacarpal and two phalanges; the rest,
ii, iii, iv, have each a metacarpal and three phalanges. A
sesamoid bone is placed beneath the metacarpo-phalangeal
joint of the three middle digits.
In the pelvic extremity, the femur, 65, is sigmoidally
bent, but in a less degree than the humerus, and is a
shorter bone. The patella is ligamentous: the synovial
joint between it and the femur is distinct from the proper
capsule of the knee-joint; the fibula, 66, is longer and more
slender than the tibia, 66; a small "fabella" is articulated
to its upper end. The proximal row of the tarsus consists
of two bones, astragalus and calcaneum, which sometimes
12




134            SKELETON OF BIRDS.
become confluent. The distal row consists of five bones,
four of which support the four normal toes, and the fifth,
a rudiment of the fifth toe without a claw: the fourth and
fifth of the second row of tarsals answer to the os cuboides
of higher animals; the other three bones to the three ossa
cuneiformia. The astragalar part of the single proximal
bone would seem to include the scaphoid as well as the
calcaneum.
In the marine chelonia, the digits of both limbs are
elongated, flattened, and united by a web; the hands and
feet having the form of fins.
In all the chelonia, the long b'ones of the limbs are solid,
without medullary cavities.
THE SKELETON OF BIRDS.
From the massive frame of the cold-blooded, heavy,
and proverbially slow tortoise, to the light, hot-blooded,
flying bird, the transition seems to be abrupt, and the
discrepancy between creatures so differently endowed extreme; nevertheless, at the confines of the feathered class,
we find some aquatic species, such as the penguin, incapable of flight, having the wings modified to act as fins,
and much resembling those of the turtle; with the bones
solid, and the feathers resembling scales. All birds, like
tortoises, lay eggs, are devoid of teeth, and have their
jaws sheathed with horn, and forming a bill or beak.
Most birds, however, enjoy the faculty of flight.
If the student of comparative osteology will procure
the skull of a rook, a hawk, a swan, or a sea-gull, and
vertically bisect it, he will have a ready instance illustrative of some of the characteristics of the osteology of




SKELETON OF BIRDS.               135
the feathered class. Such a section will show the ivorylike whiteness and compactness of the osseous tissue, and
the loose, open, cancellous structure of the bones. He
will see that air is admitted into these cancelli partly from
the nasal passages, and partly from the tympanic cavity
which receives it from the Eustachian tube; from the latter
source, the proper bones of the cranium receive their air.
Some of the characteristic features in the composition of
the skull of birds may also be noticed: as, for example,
the obliteration of all the ordinary sutures of the cranium,
except those which unite the tympanic bone, 28, to the
mastoid, 8; and that which unites the pterygoid, 23, to
the basisphenoid, 5; which sutures are speedily obliterated
in the human subject. The premaxillary is confluent
with the nasal and with the maxillary; the nasal being
confluent with the frontal and the maxillary with the
jugal. The jugal and squamosal are also confluent, and
form a long zygomatic style in all birds, connected at the
hinder extremity by a movable glenoid joint to the
outer and lower part of the tympanic. The pterygoid
articulates, in like manner, with the inner and lower part
of the tympanic, the movements of which are thus communicated to the upper mandible, so far as the junction
of the nasal with the frontal admits of such independent
motion. The upper jaw, or mandible, which includes the
vomer and nasals with the maxillary arch and appendages,
is movable in a bird through the junction of the nasals
and nasal branch of the premaxillary with the frontal, by
means of a movable articulation, or by elastic plates.
If the student will next separate one of the vertebrae
of the trunk from the rest, and cut out that portion of the
long and broad breast-bone to which its pair of ribs are




136            SKELETON OF BIRDS.
attached, he will have a segment of the skeleton, answering to that figured in Fig. 5, p. 28.
The cut surfaces will demonstrate the light cellulosity
of the divided bones. The following letters indicate the
elements of such modified vertebrae of the thorax: y, centrum, with its hyapophysis; p, parapophysis; d, diapophysis; n, neural arch and rudimental spine; pl, pleurapophysis; h, hoemapophysis; hs, hsemal spine. The tendency of individual elements and bones to coalesce in birds
has already been illustrated in the cranium; it is shown,
in most birds of flight, not only by the confluence of the
centrum with the neural arch, but by that of several consecutive centrums and arches into a single bone, in the
ample chest. In like manner the hsemal spines, which
continue distinct in many vertebrata, have here- coalesced
into a single bone, which articulates on each side with
the haemapophyses of several vertebrae. These coalesced
spines are also much developed in breadth, and send
down, from the middle of their under surface, a longitudinal crest or keel. This modification relates to the
extension of the surface for the origin of the great muscles of flight, and renders the " sternum," as the coalesced
series of hsemal spines is called, one of the most characteristic parts of the skeleton of the bird.  Ossification
extends from the neural arches into the tendons of the
vertebral muscles, and such bone-tendons, both here and
in other parts of the body, as the legs, are also characteristic of birds. The scapula- (Fig. 24), 51, is long and
slender, as in the chelonia, but is more compressed and
sabre-shaped. The coracoid, 52, as a general rule, is a
distinct bone, movably articulated to the scapula at one
end and to the sternum at the other. Its broad sternal
end here articulates by a kind of gomphosis with a deep




SKELETON OF THE SWAN.                        137
Fig. 24.
67
SKELETON OF THE SWAN (Cygnts r fertus).
12*




138          SKELETON OF THE SWAN.
groove on the fore part of the sternum. The clavicle (ib.),
58, articulates with the coracoid above, but is confluent
with its fellow and with the keel of the sternum below.
The iliac bones, 62, are remarkable for their length, and
for the number of the vertebra, or the great extent of the
confluent spinal column, to which they are anchylosed.
They reach in the swan, and in most other birds, from
the tail forwards to the vertebrae with movable ribs.
Thus the artificial characters of a "lumbar vertebra" are
wanting. The pubis and ischium on each side have
coalesced with the ilium to form the lower boundary of
the widely-perforated acetabulum. The pubis is long and
slender, joins the ischium of its own side near its lower
extremity, but does not join its fellow; thus the foramen
ovale is defined, but there is no symphysis pubis: the
absence of this symphysis facilitates the expulsion of the
large ovum with its unyielding calcareous shell. The
isehium coalesces posteriorly with the ilium, and converts
the ischiadic notch into a foramen. The caudal vertebrae,
Cl, are few in number, with broad transverse processes
formed by confluent pleurapophyses, the limits of which
may still be traced. A hemapophysis is articulated to
the lower interspace, between the fourth and fifth caudal,
and is anchylosed to the sixth. The humerus of some of
the larger birds of flight-e. g. the pelican or adjutant
crane-is remarkable for its lightness, as compared with
its bulk and seeming solidity; it is, in fact, a mere shell
of compact osseous tissue. The orifice admitting air to
its large cavity is beneath the great tuberosity at the
proximal end.
The keel is excavated, not only for the reception of an
air-cell, but likewise for a fold of the windpipe, which
fold expands with age, and lies horizontally in the sub



SIYELETON OF THE SWAN.              139
stance of the back part of the sternum. Small pneumatic
foramina are situated at the anterior and inner surface of
the bone, and perforate the articular surfaces for the sternal ribs.
In the skeleton of the wild swan (Cygnus ferns) (Fig.
24), here selected as an illustration of the ornithic modification of the vertebrate type, there are not fewer than
twenty-eight vertebrae,'c s D, between the skull and the
sacrum, the last six of which, DD, support movable ribs;
of these, the first and second pairs are free; the -next four
are articulated to the sternum by bony heemapophyses;
the last five pairs of ribs are attached to the sacrum, and
also to the sternum; but the tenth, or last rib on the left
side, is very rudimentary, being only about one inch in
length. There are eight caudal vertebra, Cd. The trachea,
or windpipe, penetrates the sternum, and bends and winds
in the interior of the bone before returning to enter the
chest. The apex of the furculum, 58, bends upwards,
and forms a hoop over the windpipe as it enters into the
keel of the breast-bone. The furculum, sometimes called
"merrythought," consists of the two clavicles confluent
at their lower free ends. If a portion of the one side of
the sternum be removed, the tortuous trachea which it
incloses will be exposed. To the great length and peculiar course of the windpipe in this species is to be attributed its remarkably loud and harsh voice; whence the
name hooper, or whistling swan, has been derived; and
is applied in contradistinction to the domestic or mute
swan, in which, as in most other birds, the trachea proceeds at once to the lungs, without entering the sternum.
In the female of the wild species, the course of the trachea is much more limited than in the male, seldom




140      SKELETON OF THE DUCK TRIBE.
penetrating the sternum to a greater extent than from
three to four inches.
The breadth of the sternum, and the strong ridge or
keel that descends from the midline of its under surface,
relate to the increased extent of surface required for the
attachment of the "pectoral" muscles, which are the active organs of flight. In the land-birds devoid of the
power of flight, such as the ostrich and apteryx, the keel
is wanting and the sternum is short. Its various proportions, processes, notches, and perforations render it a very
characteristic bone in birds.
In no order, founded upon modifications of the feet, is
the sternum more diversified in character than in the
palmipedes or web-footed order; for in none are the
powers of flight enjoyed in such different degrees, or exercised in such various ways, from the frigate-bird down
to the penguins, where the power of flight is abrogated,
and the rudimental wings used as fins.
In the goose and duck tribes, as well as the swans
(anseres, Linn.), the sternum is long and broad, and presents
two moderately wide and deep hind notches; the costal
processes are usually subquadrate; the coracoid grooves
are continued into one another at the median line; the
costal tract forms about half of the lateral margin in the
ducks and geese, and two-thirds or more in the swans;
the interpectoral ridge extends from the prominent part
of the coracoid margin backwards, nearly parallel to the
lateral margin, to the inner side of the lateral grooves;
the back part of the sternum between the grooves is quadrate, with the angles slightly produced in most; there is
a short manubrial process below the coracoid groove.
The form of the sternum, its long keel, and the backward
production of the long and slender ribs, give a boatlike




SKELETON OF THE DUCK TRIBE.             1.4
figure to the trunk of these swimming-birds, which is
well adapted to their favorite medium and mode of locomotion. The bones of the wing or anterior extremity do
not present that extraordinary development which might
be expected from the powers of the member of which
they form the basis. The great expanse of the wing is
gained at the expense of the epidermoid system (quills
and feathers, like hairs and scales, are thickened epiderm),
and is not exclusively produced by folds of the skin requiring elongated bones to support them, as in the flyingfish, flying-lizards, and bats. The wing-bones of birds
are, however, both in their forms and modes of articulation, highly characteristic of the powers and applications
of the muscular apparatus requisite for the due actions
of flight. The bones of the shoulder consist on each side
of a scapula, 51, a coracoid, 52, and a clavicle, 58, the
clavicles being, as a general rule in birds, confluent at
their median ends, and so forming a single bone called
"furculum," or "os furcatorium;" this further modification
of the hamal arch in birds, repeating that of the pubis
and lower jaw in some other animals, having occasioned
an additional specific term in ornithotomy. The scapula,
51, is a long, narrow, flat sabre-shaped plate, expanded at
the humeral end, where it forms externally part of the
joint for the arm-bone called "glenoid cavity," and extended backwards nearly parallel with the vertebrae, as
far as the ilium, 62, in the swan, and reaching to the last
rib in the swift; but it is much shorter in the birds incapable of fight. The coracoid is the strongest of the
bones of the scapular arch: it forms the anterior half of
the glenoid cavity, extends above this part to abut upon
the furculum, and is continued downwards below the
joint, expanding, to be fixed in the transverse groove at




142      SKELETON OF THE DUCK TRIBE.
the fore part of the sternum; it thus forms the chief
support of the wing, and the main point of resistance
during its downward stroke. In the hawks and other
birds of prey, and in the crows and most passerine birds,
a small bone (os humero-capsulare) extends between the
scapula and coracoid along the upper part of the glenoid
cavity; this is absent in the swan and other swimmers,
as well as in the gallinaceous and wading birds. The
humerus, 53, is usually a long and slender bone, but is
not always developed in length in proportion to the powers of flight; for, although it is shortest in the struthious
birds and penguins, it is also very short, but much thicker
and stronger in the swift and humming birds. The head
of the humerus is transversely oblong and convex; it is
further enlarged by two lateral crests; of these the superior is the longest, and is bent outwards; the inferior is
thickened and incurved, and beneath it is situated the
orifice by which the air penetrates the cavity of the bone.
The articular surface at the opposite or "distal" end is
divided into two parts, one internal, for the ulna, of a
hemispheric form, the other also convex, but more elongated and oblique, extending some way upon the anterior
surface of the humerus. The extremity of a long bone of
a limb which is next the trunk is called the "proximal"
one; the extremity furthest from the trunk, the "distal"
one; they are not always "upper" and "lower."  The
ulna, 55, glides upon the inner hemispheric tubercle, upon
the trochlear canal, and on the back part of the outer convexity. A ligament, extending fromn the outer part of
the head of the radius to the outer part of the olecranon,
above the posterior margin of the outer division of the
articular surface of the ulna, plays upon the back part of
the radial convexity of the humerus and completes the




BONES OF THE WING.               143
cavity receiving it. The ulna is always stronger than the
radius; but both are long, slender, and nearly straight
bones, so articulated together as to admit of scarcely any
rotation which adds to the resisting power of the wing
in the action of flight. The upper part of the ulna, or
"olecranon," is short.  In the tendon attached to it, a
separate ossicle is developed in the swift, and two such
bones in the penguin. The ulna is often impressed by
the insertions of the great quill-feathers of the wing.
The bones of the hand are very long and narrow, with
the exception of the two distinct or unanchylosed carpal
bones; these are so wedged in between the antibrachium,
54, 55, and the metacarpus, 57, as to limit the motions of
the hand to abduction and adduction, or those necessary
for folding up and spreading out the wing. The hand is
thus fixed in a state of pronation; all power of flexion,
extension, and rotation is removed from the wrist-joint;
so that the wing strikes firmly, and with the full force of
the depressed muscles, upon the resisting air. The part
of the hand numbered 57 in Fig. 24 includes the metacarpal bones of the digits answering to the second, third,
and fourth of the pentadactyle members, which are confluent at their proximal ends with each other, and with
the "os magnum," one of the carpal bones, now forming
the convex base of the middle metacarpal. This metacarpal, and that answering to the "fourth" digit, are of
equal length, and are also confluent at their distal ends;
but the middle or " third" metacarpal is much the strongest. That answering to the "second" digit, ii, is very
short, and like a mere process from the third; it supports
two short phalanges in the swan. The third metacarpal
supports three phalanges, iii, the fourth a single phalanx,
iv. All these are wrapped up in a sheath of integument,




144           BONES OF THE WING.
and are strongly bound together; so that the wing loses
nothing of its power, whilst so much of the typical structure of the-member is retained, that evelry bone can be
referred to its corresponding bone in the most completely
developed hand.
In ornithology, the large quill-feathers that are attached
to the ulnar side of the hand are termed " primarim," or
primary feathers; those that are attached to the forearm
are the "secuudarim," or secondaries, and "tectrices," or
wing-coverts; those which lie over the humerus are called
" scapularia," or scapularies; and those which are attached
to the short outer digit, ii, erroneously called the " thumb,"
are the "spurire," or bastard feathers. The bones of the
leg do not present the same number of segments as those
of the wing, that corresponding with the carpus being
wholly blended with the one-that succeeds.
The pelvic bones offer this contrast with those of the
shoulder, that they are always anchylosed on either side
into one piece, "os innominatum," and.not at the median
line, whilst this is the only place where the elements of
the scapular apparatus are united by bone. In the young
bird, the os innominatum is composed of three bones.
The ilium, 62, is flattened, elongated, usually anchylosed
to a very long sacrum; it forms the upper half of the
joint for the thigh-bone, called "cotyloid cavity."  The
pubis, 64, is very long and slender; it does not meet its
fellow at the middle line in any bird save the ostrich, but
is directed backwards, with its free extremity bent downwards. The pelvis of the ostrich is so vast, that the pubic
junction completing it does not impede the exit of the
egg; in other birds the open pelvis facilitates the passage
of that large and brittle generative product. The ischium,
63, is a simple elongated bone, extending from the coty



PELVIS AND BONES OF THE LEGS OF BIRDS. 145
loid cavity backwards, parallel with the ilium; it sometimes coalesces, as in the swan, with both the ilium and
pubis at its distal end.
The cotyloid cavity is incomplete behind, and is closed
there by ligament. The femur, 65, is a short, cylindrical,
almost straight bone; the head is a small hemisphere,
presenting at its upper part a depression for the "round
ligament."  The single large " trochanter" generally rises
above the articular eminence, and is continuous with the
outer side of the shaft. The orifice for the admission of
air is situated in the depression between the trochanter
and head. The distal end presents two condyles, the
inner one for the inner condyloid cavity of the tibia; the
outer one-for the outer cavity of the tibia and for the
fibula; the outer condyle is produced into a semicircular
ridge, which passes between the tibia and fibula; this
ridge puts the outer elastic ligament on the stretch, when
the fibula is passing over the condyle, and the fibula is
pulled into a groove at the back of the condyle, with a
jerk, when in extreme flexion; this spring-joint is well
exemplified in both the swan and water-hen.
The proximal end of the tibia is divided into the two
shallow condyloid cavities above noticed: two ridges are
extended from its upper and anterior surface: the
strongest of these is the "procnemial" ridge, and is
slightly bent outwards; the shorter one on the outside of
this is the " ectocnemial" ridge; they are usually united
above by a transverse ridge, called "epicnemial" ridge;
this is developed into a long process in the divers, grebes,
and guillemots: a fibular ridge projects slightly from the
upper third of the tibia for junction with the fibula. The
distal end of the tibia forms a transverse pulley or trochlea, with the anterior borders produced. Above the fore
13




146 PELVIS AND BONES OF THE LEGS OF BIRDS.
part of the trochlea is a deep depression, and in many
birds an osseous bridge extends across it.
The third segment of the leg, 69, is a compound bone,
consisting originally of one proximal piece, short and
broad, presenting two articular concavities to the two thick
and round borders of the tibial trochlea, of three metatarsals which coalesce with each other and with the above
tarsal piece, and of one or more bony processes which are
ossified from the back part of the proximal piece, or from
the proximal ends of the metatarsals, and which, from
their relations to the extensor tendons, are called "calcaneal" processes.  In most birds, a small rudimental
metatarsal, supporting the innermost toe, or "hallux," i,
is articulated by ligament with the innermost of the
coalesced metatarsals, and is properly included in the
same segment of the limb. The three principal metatarsals are interlocked together before they become anchylosed, the middle one being wedged into the back part of
the interspace of the two lateral'ones above, and into the
fore part below, passing obliquely between them. The
period at which these several constituents of the "tarsometatarse" coalesce is shorter in the birds that can fly
than in those that cannot; and the extent of the coalescence is least in the penguins, in which the true nature of
the compound bone is best seen.
The modifications of the tarso-metatarse are chiefly
manifested in its relative length and thickness, in the
relative length of the three metatarsals, and in the number
and complexity of the calcaneal processes.
The inner of the two cavities for the condyles at the
proximal end of the bone is the "entocondyloid" cavity
or surface, the outer one the " ectocondyloid" surface; they
are separated by an "intercondyloid" tract, from the fore



STRUCTURE OF THE FOOT IN BIRDS.    147
part of which there usually rises an intercondyloid tuberosity. The entocondyloid cavity is usually the largest
and deepest: it is so in the raven, in which the base of the
intercondyloid tubercle extends over the whole of the intercondyloid space. There are three calcaneal processes:
one, called the "entocalcaneal," projects from below the
entocondyloid cavity, and from the back part of the upper
end of the entometatarse; a second, called the "mesocalcaneal," from the intercondyloid tract and the mesometatarse, and the third called " ectocalcaneal," from behind
the ectocondyloid cavity and the ectometatarse. These
three processes are united together by two transverse
plates circumscribing four canals, two smaller canals being
further carried between the ento and meso-calcaneal processes. The primitive interosseous spaces are indicated
by two small foramina at the upper and back part of the
shaft, which converge as they pass forward, and terminate
by a single foramen at the fourth part of the anterior concavity. A similar minute canal is retained between the
outer and middle metatarsals, near their distal ends; each
metatarsal then becomes distinct, and develops a convex
condyle for the proximal phalanx. The middle one is
the largest, and extends a little lower than the other two:
it is also impressed by a median groove; the more compressed lateral condyles are simply convex, and are of
equal length. A rough surface, a little way above the
inner condyle, indicates the place of attachment of the
small metatarsal of the hallux.
In the swan and other anserine birds the calcaneal
prominence presents four longitudinal ridges, divided by
three open grooves, the innermost ridge being the largest;
the shaft is subquadrate, with the angles rounded, and
none of the surfaces are channelled. The inner condyle




148   STRUCTURE OF THE FOOT IN BIRDS.
scarcely extends before the base of the middle one; the
canal perforating the outer intercondyloid space is
bounded below by two small bars passing from the middle to the outer condyle, and which bars define the groove
for the abductor muscle of the outer toe.
The tarso-metatarse of the diver (colymbus) is remarkably modified by its extreme lateral compression. The
ento and ecto-calcanea are prominent, oblong, subquadrate plates, inclining towards each other, but not quite
circumscribing a wide intermediate space. The broad
outer and inner surfaces of the shaft are nearly fiat; the
narrow fore and back surfaces are channelled; the anterior groove leads to the wide canal, perforating obliquely
the shaft above the outer intercondyloid space, from
which a narrower canal conducts to that interspace. The
middle and outer trochleve are nearly equally developed;
the inner one stops short at the base of the middle one.
The number of toes varies in different birds; if the spur
of the cock be regarded as a rudimental toe (which is not,
however, my view of it), it may be held to have five toes,
while in the ostrich the toes are reduced to two. Birds,
moreover, are the only class of animals in which the
toes, whatever be their number or relative size, always
diffir from one another in the number of their joints or
phalanges, yet at the same time present a constancy in
that variation.
The innermost or back toe, i (Fig. 24), answering, as I
believe, to the "hallux," or innermost digit of the pentadactyle foot, has two phalanges; the second toe, ii, has
three, the third toe, iii, four, and the fourth toe, iv, five
phalanges. I believe the toe answering to the fifth in
lizards and other pentadactyle animals to be wanting in
the bird's foot; and the spur, sometimes single, sometimes




3MECHANISM OF FLIGHT IN BIRDS.    149
double, as in Pavo bicalcaratus, to be a superadded weapon
to the metatarse. As the toes in the tridactyle emeu,
cassowary, and bustard, have respectively three phalanges,
four phalanges, and five phalanges, we recognize them as
answering to the second, third, and fourth in other birds;
the toes in the didactyle ostrich have respectively four
and five phalanges, and what is here truly suggestive, the
outermost, which is much the smallest and shortest toe,
has the greater number of joints, viz: five, thus retaining
its ornithic type, as the fourth, or outermost, toe.
The entire form of the body, and consequently that of
its bony framework, in a bird, has special reference to
the power of flight. The trunk is an oval with the large
end forwards. The vertebral column of this part is short
and almost inflexible, so that the muscles act to great advantage; the spine of the neck being long and flexible,
the-centre of gravity is readily changed from above the
feet —as when standing or walking —to between and beneath the wings during flight; when suspended in the air
the bird's body naturally falls into that position, which
throws the centre of gravity beneath the wings. The axis
of motion being situated in a different place in the line of
the body when walking fromthat which is used when flying,
the discrepancy requires to be compensated by some means
in all birds, in order to enable them to perform flight
with ease. Raptorial birds take a horizontal position
when suspended in the air, and the compensating power
consists in their taking a more or less erect position when
at rest. Another class, including the woodpeckers, wagtails, &c., take an oblique position in the air; with these
the compensating power consists in their cleaving and
passing through the air at an angle coincident with the
position of the body, and performing flight by a series of
Y7gPih b     sreso




150     MECHANISM  OF FLIGHT IN BIRDS.
curves or saltations. Natatorial birds sometimes need
very extended flight; they take a very oblique position
in the air, stretch out their legs behind and their neck in
front; they have the ribs greatly lengthened, the integuments of the abdomen are long and flexible, which enables
them greatly to enlarge the abdominal portion of their
bodies by inflating it with air; this causes a decrease in
the specific gravity of that part, and raises it to a horizontal position; the compensating power consists in the
posterior half of the body becoming specifically lighter,
while the specific gravity of the anterior half remains unaltered. When they alight they drop the legs, throw back
the trunk by bending the knee-joint, and bring the head
over the trunk by a graceful sigmoid curve of the long
neck, as in Fig. 24. The act of swimming is rendered
easy by the specific gravity of the body, by the boatlike
shape of the trunk, and by the conversion of the hinder
extremities into oars, in consequence of the membranes
uniting the toes together. The effect of these web-feet in
water is further assisted by the toes having their membranes lying close together when carried forwards; whilst,
on the contrary, they are expanded in striking backwards.
The oarlike action of the legs is still further favored by
their backward position-an arrangement, however, which
is unfavorable for walking.
Borelli was the first who, by comparison of the anatomical peculiarities of the human frame and the structure
of birds, demonstrated, to a certain extent, the impossibility of the realization of the cherished project of flying
by man. He arrived at this conclusion from a comparison of the form and strength of the muscles of the wings
of birds with the corresponding muscles of the human
body.




VARIOUS FORMS OF LIMBS IN MAMMALS. 151
PRINCIPAL FORMS OF TEIE SKELETON IN
TIHE CLASS MAMMALIA.
In the class Mammalia, which includes the hairy quadrupeds with the naked apodal whales and biped man, the
form of the animal is modified for a great diversity of
kinds and spheres of locomotion. Some live exclusively
in the ocean, and cleave the liquid element iunder the form
and with the locomotive powers of fishes; some frequent
the fresh waters; some pass a subterraneous existence, and
work their way through the solid earth; some mount aloft,
to seek and seize their prey in the air; some pass their
lives in trees; most, however, dwell on the earth, with
various powers of walking, running, and leaping. Lastly,
man is modified to sustain his frame erect on the hinder,
now become in him the lower, limbs.
In the Mammalian class, accordingly, we find the limbs
progressively endowed with more varied and complicated
powers. They retain in the Cetacea (whale and porpoise
tribe) their primitive form of flattened fins; in the Ungulata (hoofed beasts) one or more of the digits acquire
the full complement of joints, but have the extremity enveloped in a dense hoof; in the Unguiculata (quadrupeds
with claws), the limbs, with ampler proportions, have the
digits liberated, and armed with claws confined to the
upper surface, leaving the under surface of the toes free
for the exercise of touch; in the mole, the hand is
shortened, thickened, expanded, and converted into a
sort of spade; in the bat, the fingers are lengthened,
attenuated, and made outstretchers and supporters of a
pair of wings; in the Quadrumana (ape and monkey




152 VARIOUS FORMS OF LIMBS IN MAMMALS.
tribes), certain digits are endowed with special offices, and
by a particular position enabled to oppose the others, so
as to seize, retain, and grasp. Lastly, in Man, the offices
of support and locomotion are assigned to a single pair
of members; the anterior, and now the upper, limbs being
left free to execute the various purposes of the will, and
terminated by a hand, which, in the matchless harmony
and adjustment of its organization, is made the suitable
instrument of a rational being.
In contemplating and comparing the skeletons of a
series of mammals, the most striking modifications are
observable in the structure and proportions of the limbs.
There are a few osteological characters in which all
mammalia agree, and by which they differ from the lower
vertebrata; and some have been supposed to be peculiar
to them that are not so. The pair of occipital condyles,
e. g., developed from the exoccipitals, are a repetition of
what we saw in the batrachia. The flat surfaces of the
bodies of the trunk-vertebrse were a character of many
extinct reptiles; but these surfaces in mammals are developed on separate epiphysial plates, which coalesce in
the course of growth with the rest of the centrum. Movable ribs, projecting freely (pleurapophyses) in the cervical
region, may be found in a few exceptional cases (sloths,
monotremes); bony sternal ribs (hemapophyses) exist in
most Edentata; a coracoid extending, as in birds and
lizards, from the scapula to the sternum, with an "epicoracoid," as in lizards, is present in the monotremes
(platypus or duck-mole, and echidna or spiny ant-eater,
of Australia); the cotyloid cavity may be perforated in
the same low mammals as in birds; the digits may have
the phalanges in varying number in the same hand, and
exceeding three in the same finger, e. g., in the whale




SKELETON OF THE WHALE.              153
tribe. But the following osteological characters are both
common and peculiar to the mammalia. The squamosal,
27, or second bone of the bar continued backwards from
the maxillary arch, is not only expanded as in the chelonia, but develops the articular surface for the mandible,
and this surface is either concave at some part or is flat.
Each half or rainus of the mandible is ossified from a
single centre, and consists of one piece; and the condyle
is either convex or is flat, never concave. The presphenoid (centrum of the parietal vertebra) is developed distinctly from the basisphenoid; it may become confluent,
but is not connate, therewith.
One known mammal (the three-toed sloth) has more,
and one (the manatee, or sea-cow) has less than seven
vertebrae of the neck.  In the rest of the class these
vertebrae, which have the pleurapophyses short and
usually anchylosed, are seven in number.
SKELETON IN TIIE CETACEA, OR WIIALE TRIBE.
In the skeleton of the whale (Fig. 25), which to outward appearance seems to have as little neck as a fish,
there are as many cervical vertebrae as in the long-necked
giraffe: this is a very striking instance of adherence to
type within the limits of a class: the adaptation to form
and function is effected by a change of proportion in the
bones; the cervical vertebrae in the whale are flattened
from  before backwards into broad thin plates; in the
giraffe (Fig. 30) they are produced into long subcylindrical bones. In the whales, the movements of these
vertebrae upon one another are abrogated; and in the
grampus and porpoise, the seven vertebrae are blended




154         SKELETON OF THE WHALE.
together into a single bone; they thus give a firm and
unyielding support to the large head, which has to overcome the resistance of the water when the rapid swimmer
is cleaving its course through that element.  The dorsal
Fig. 25.
j7s
FORESHORTENED VIEW OF THE SKELETON OF A WHALE (Balcenoptera boops),
SHOWING ITS RELATIVE SIZE TO MAN.
vertebrae are characterized in all mrammalia by the sudden
increase in the length and size of the ribs, which, in a
certain number of these vertebrae, including the first, are
joined to a breast-bone by a commonly cartilaginous,
rarely osseous, part. The first rib is remarkable for its
great breadth in the whale; this and a few following ribs
are joined to a short and broad and often perforated sternum (Fig. 25), No. 60; the remaining ribs are free, or, as
they would be called in Human Anatomy, " false." They
are articulated to the ends of diapophyses, which progressively increase in length to the last of the dorsal
series. Then follow vertebrae without ribs, answering to
those called "lumbar."   The whole hinder part of the
trunk of whales being needed to effect the strokes by
which they are propelled, its vertebrae are as free from
anchylosis as in fishes; there is consequently no " sacrum,"
and the caudal vertebra are counted from the first of




SKELETON' OF THE WHALE.             155
those that have "chevron bones" articulated to their
under part. This special name is given to the vertebral
elements called "hbemapomophyses" (see Fig..26, h),
which are articulated in cetacea as in crocodilia, directly
to the under surface of the centrum, and, coalescing at
their opposite ends, develop thence a " haemal spine," and
form a " haemal" canal analogous to, but not homologous
with, that in fishes (compare No. V,- h, with No. I, p, in
Cut 10, p. 182). The caudal vertebrae of whales further
differ from those in fishes in retaining the transverse processes, and in becoming flattened from above downwards,
without coalescing. These modifications relate to the
support of a caudal fin, which is extended horizontally
instead of vertically.
Whales and porpoises progress by bounding movements or undulations in a vertical plane, and their necessity of coming to the surface to inhale the air directly, as
warm-blooded mammals, calls for a modification in the
form of the main swimming instrument, such as may best
adapt it to effect an easy and rapid ascent of the head.
The course of the whale is stopped and modified by
the action of the pectoral limbs, which are the same
parts as those in fishes, but constructed more after the
higher vertebrate type. The digital rays do not exceed
five in number; but they consist of many flattened phalanges, and are enveloped in a common sheath of integument. A radius, 55, and an ulna, 54 (Fig. 25), support
the carpal series; but, instead of being directly articulated
to the scapular arch, they are suspended to a humerus,
53: this is a short, thick bone, with a rounded head.
The scapula, 51, is detached from the occiput, has a short,
stunted, coracoid anchylosed to it, and is thus freely suspended in the flesh; it develops an acromial process: the




156        SKELETON OF THE DUGONG.
ulna, 54, is produced upwards into an olecranon. With
all those marks, however, of adhesion to the mammalian
type of forearm, the outward aspect of the limb is as
simple as is that of the fish's fin; it moves, as by one
joint, upon the trunk, and is restricted to the functions of
a pectoral fin.
In the huge skull of the whale, the broad vertical occiput may be noticed, by which the head is connected,
through the medium of a short, consolidated neck, with
the trunk; the whole cranium seems to have been compressed above, from before backwards, so that the small
nasal bones, 15, articulating with the short and very broadc
frontals, form the highest part of the skull. The long
maxillaries, 21, and premaxillaries, 22, extend backwards
and upwards, to articulate with the nasals, and complete
with them the bony entry to the air-passages, situated so
favorably at the summit of the cranium. The nostrils,
formed by the soft parts guarding that entry, are called
"blow-holes;" they are double in the whales —single in
the smaller cetacea. In the whales, the "baleen," or'whalebone" plates are attached to the palatal surface
of the maxillary and premaxillary bones; the expanded
toothless mandible supports an enormous under lip,
which covers the whalebone plates when the mouth is
shut. The skeleton of the great finner whale (BalEnoptera boops), from which the foreshortened view (Cut
25) is taken, was ninety-six feet in length; the relative
dimensions of man is given by the: outlines of the skeleton at its side. No known extinct animal of any class
equalled this living Leviathan in bulk.
There are a few whalelike mammals, equally devoid of'
rudiments of hinder limbs, which obtain their sustenance
from  sea-weeds or seaside herbage. They have teeth




SKELETON OF THE DUGONG.               157
adapted for bruising such substances, and the movements
of the head in grazing require the cervical vertebrae to be
unanchylosed; these are, however, short, and in the manatee but six in number. In the dugong (Fig. 26), one
of these herbivorous sea-mammals frequenting the Malayan and Australian shores, the upper and lower jaws
are singularly bent down, and the upper jaw is armed
with a pair of short tusks. The bones of all these cetacea
are singularly massive and compact. Three or four of
the anterior thoracic ribs are joined to a sternum-the
rest are free. One of the vertebrae intervening between
the costal and caudal series has connected with it a simple
pelvic arch, in which the ilium and ischium may be recognized, and a still more rudimental condition of such
arch is suspended in the inguinal muscles of the true
cetacea. Most of the caudal vertebrae (Fig. 26), cd, of the
Fig. 26.
SKrLETON OF THE D lcore A
SKELETON OF THE DIUGONG (IIallcore Amlstralis).
manatee and dugong, have long diapophyses, and haemal
arches (Fig. 26), h. The terminal vertebrae are flattened
horizontally.
The lacteal organs of the dugong are placed on the
breast, and the pectoral fins, in the female at least, are
14




158          SKELETON OF THE SEAL.
applied to clasp the young; and the animal so observed,
with its own head and that of its young above water, has
given rise to the fable of the siren and mermaid. The
bones and joints of the pectoral fin are accordingly better
developed than in the ordinary whales. The first row of
carpal bones, 56, consists of two-one articulated to the
radius, 55, the other to the ulna, 54, and fifth digit, 57, v,
and both to the single bone representing the second row.
The first digit, i, consists of a short metacarpal; the metacarpals of the others support each three phalanges.
SKELETON OF THE SEAL.
In the seal tribe (Phocidce), another and well-marked
stage is gained in the development of the terrestrial instruments of locomotion. Hind limbs are now addedthe marine mammal has become a quadruped. The
sphere of life of the seals is near the shores; they often
come on land; they sleep and bring forth among the
rocks and littoral caves: hence the necessity for a better
development of the pectoral limbs, although these, like
the pelvic ones, still retain the general form of fins. The
fish-hunting seals make more use of the head in independent movements of sudden extension, retraction, and
quick turns to the right and left, than do the cetacea of
like diet; and the walrus (Fig. 27) works the head, as the
place of attachment of its long, vertical, down-growing
tusks, in various movements required in climbing over
floes and bergs of ice. Accordingly, in the seal tribe, we
find the seven neck-vertebraa (ib.) c, longer, and with more
finished and free-playing joints than in the whales and
dugongs. The sigmoid curve, in which they can be




SKELETON OF THE WALRUS.                 159
thrown during retraction of the head, exceeds that in most
other mammals, and almost reminds one of the extent of
flexion of this part of the spine in birds.
Fig. 27.
SKELETON OF THE WALRUS (Tr'ic~ec~ts r-osmarus).
In the walrus, the skeleton of which is here selected to
exemplify the phocal modification of the mammalian skeleton, the vertebral formula is: 7 cervical, C, 11 dorsal, D,
5 lumbar, L, 3 sacral, S, and 9 caudal, cd. As, in consequence of the presence of hind-limbs, a sacrum is now
established, the characters of the above five kinds of
body-vertebrae, as defined in man and other mammals,
may here be given: the cervical or neck-vertebrae " have
perforated transverse processes," the dorsal vertebrae
"bear ribs;" the lumbar vertebrae "have imperforate
transverse processes and no ribs;" the sacral vertebrae
"are anchylosed together;" the rest are caudal vertebrae,
whatever their modifications.  In the above characters,
the term "rib" is given to the vertebral element called
"pleurapophysis," when this is long and movable; that




160  SKELETONS OF THE SEAL AND WALRUS.
element may be, and often is, present, but short and fixed,
in both cervical, lumbar, sacral, and caudal vertebrae; in
some mammals, e. g. monotremes, the pleurapophysis may
remain unanchylosed in some of the neck-vertebrm, but
it is short, like a transverse process; and the so-called
"perforated transverse process" in all mammals consists
of the diapophysis, parapophysis, and pleurapophysis;
the hole being the interval between those parts; in the
lumbar vertebrae the pleurapophysis is short, and confluent or connate with the diapophysis.
Returning to the skeleton of the walrus, we find that
nine pairs of ribs directly joih the sternum, which consists of eight bones. The transverse processes of the last
cervical are imperforate, consisting of the diapophysis
only. The neural arches of the middle dorsal vertebrae
are without spines and very narrow, leaving wide unprotected intervals of the neural canal. The bones of the
neck are modified to allow of great extent and freedom
of inflection. The perforated transverse processes of the
third to the sixth cervicals inclusive are remarkable for
the distinctness of their constituent parts. Inferior ridges
and tuberous processes, called "hypapophyses," are developed from some dorsal and lumbar vertebra. These
processes indicate the great development of the anterior
vertebral muscles, e. g. the "longi colli" and "psose," and
relate to the important share which the vertebrae and
muscles of the trunk take in the locomotion of the seatribe, especially when on dry land, where they may be
called "gastropods," in respect of their peculiar mode of
progression. The walrus alone seems to have the power
of supporting itself on the fore fins, so as to raise the
belly from the ground. There is no trace of clavicle in
any seal. The upper part of the scapula exceeds the




SKELETONS OF THE SEAL AND WALRUS. 161
lower one in breadth. The spine terminates by a short
and simple acromion. The humerus is short and thick,
and is remarkable for the great development of the inner
tuberosity and of the deltoid ridge, which is deeply excavated on its outer side. The inner condyle is perforated. The scaphoid and lunar bones are connate.
Although the pollex or the first digit exceeds the third,
fourth, and fifth in length, it presents its characteristic
inferior number of phalanges, by which the front bdrder
of the fin is rendered more resisting. The pelvic arch is
remarkable for the stunted development of the ilia, and
the great length of the ischia and pubes. The femur is
equally peculiar for its shortness and breadth. The tibia
and fibula present the more usual proportions, and are
anchylosed at their proximal ends. The bones of the
foot are strong, long, and are modified to form the basis
of a large and powerful fin: the middle toe is the shortest,
and the rest increase in length to the margins of the foot;
the inner toe has, nevertheless, but two phalanges, the
rest having three phalanges, whatever their length; and
this is the typical character, both as to the number of the
digits and their joints, in both fore and hind feet of the
mammalia.
In the living walrus and seal, the digits of each extremity are not only bound together by a common broad
web of skin, but those of the hind-limbs are closely connected with the short tail: being stretched out backwards, they seem to form with it one great horizontal
caudal fin, and they constitute the chief locomotive organ
when the animal is swimming rapidly in the open sea.
The long bones of seals, like those of whales, are solid.
WVith regard to the skull in the seal-tribe, it may be
remarked that an occipitosphenoidal bone is formed, as
14*




162         SKELETON OF THE HORSE.
in man, by the coalescence of the basioccipital with the
basisphenoid; the parts of the dura mater or outer membrane of the brain, called "tenlorium," with the posterior
part of the " falx," are ossified. The sella turcica is shallow, but well defined behind by the overhanging posterior clinoid processes: the petrosal shows a deep, transverse, cerebellar fossa, and is perforated by the carotid
canal. The frontal forms a small rhinencephalic fossa,
and contributes a very large proportion to the formation
of the orbital and olfactory chambers.
In Fig. 27, 62 is the ilium, 63 the ischiurn, and 64 the
pubes, 65 is the femur or thigh-bone, 66 the tibia, 66' the
patella or kneepan, 67 the fibula, 68 the tarsus, and 69
the metatarsus and phalanges of the hind-foot; the numbers on the other bones correspond with those in the
skeleton of the dugong.
SKELETONS OF IIOOFED QUADRUPEDSTHE HORSE.
The contrast, as regards the sphere of life and kind of
movement between the seal and the horse is very great;
the instruments of locomotion, and indeed the whole
frame, need to be very different in an animal that can
only shuffle on its belly along the ground, and one that
can traverse the surface of the earth at the rate of four
miles in six minutes and a half, as was achieved by the
noted racer "Flying Childers." The modifications in the
form and proportions of the locomotive members are
accordingly extreme. The limbs in the horse are as
remarkable for their length and slenderness, as in the
seal for their brevity and breadth. Both fore and hind
limbs in the horse terminate each in a single hoof; the




SKELETON OF THE HORSE.               163
trunk is raised high above the ground, and is more remnarkable for its depth than breadth, especially at the
fore part; the neck is long and arched; the jaws long
and slender, being produced so as to facilitate the act of
cropping the grass, and leaving so much space between
Fig. 28.
INN
/411"  i.
footed ally, as the ship is steered by the helm.
Were every animal constructed expressly and exclusively for its own peculiar habits of life, and irrespective
of any common pattern, it could scarcely be expected,




164         SKELETON OF THE HORSE.
beforehand, that the same bones would be found in the
horse as in the seal; yet a comparison of their skeletons,
Cuts 27 and 28, will demonstrate that this is, to a very
great degree, the case.
The vertebral formula of the horse is: 7 cervical, C,
19 dorsal, D, 5 lumbar, L, 5 sacral, S, and 17 caudal.
Eight pairs of ribs directly join the sternum, 60, which
consists of seven bones and an ensiform cartilage. The
neural arches of the last five cervical vertebra  expand
above into flattened, subquadrate, horizontal plates of
bone, with a rough tubercle in place of a spine: the zygapophyses, z, are unusually large. The perforated transverse process sends a pleurapophysis, pt, downwards and
forwards, and a diapophysis, d, backwards and outwards,
in the third to the sixth cervicals inclusive: in the seventh
the diapophysial part alone is developed, and is imperforate. The spinous processes suddenly and considerably
increase in length in the first three dorsals, and attain
their greatest length in the fifth and sixth, after which
they gradually shorten to the thirteenth, and continue of
the same length to the last lumbar. The lumbar diapophyses are long, broad, and in close juxtaposition; the
last presents an articular concavity adapted to a corresponding convexity on the fore part of the diapophysis of
the first sacral. The scapula, 51, is long and narrow, and
according to its length and obliquity of position the muscles attached to it, which act upon the humerus, operate
with more vigor, and to this bone the attention of the
buyer should be directed, as indicative of one of the good
points in a horse. The coracoid is reduced to a mere
confluent knob. The spine of the scapula, 51, has no
acromion. The humerus, 53, is remarkable for the size
and strength of the proximal tuberosities in which the




SKELETON OF THE HORSE.             165
scapular muscles are implanted. The joint between it
and the scapula is not fettered by any bony bar connecting the bladebone with the breastbone; in other words,
there is no clavicle. The ulna, represented by its olecranal
extremity, 54, is confluent with the radius, 55. The os
magnum in the second series of carpal bones, 56, is remarkable for its great breadth, corresponding to the
enormous development of the metacarpal bone of the
middle toe, which forms the chief part of the foot. Splintshaped rudiments of the metacarpals, answering to the
second, ii, and fourth, iv, of the pentadactyle foot, are
articulated respectively to the trapezoides and the reduced
homologue of the mnciforme. The mid-digit, iii, consists
of the metacarpal called " cannon-bone," and of the three
phalanges, which have likewise received special names in
Veterinary Anatomy, for the same reason as other bones
have received them in Human Anatomy. " Phalanges" is
the "general" term of these bones, as being indicative of
the class to which they belong, and "haemapophyses" is
the "general" term of parts of the inferior arches of the
head-segments; and just as, from the modifications of these
haemapophyses, they have come to be called "maxilla,"
"mandibula," "ceratohyal," &c., so the phalanges of the
horse's foot are called-the first, "great pastern bone,"
the second, "small pastern bone," and the third, which
supports the hoof, the "coffin bone;" a sesamoid ossicle
between this and the second is called the "coronary."
The ilium, 52, is long, oblique, and narrow, like its homotype, the scapula; the ischium, 63, is unusually produced
backwards. The extreme points of these two bones show
the extent to which the bending muscles and extending
muscles of the leg are attached; and according to the
distance of these points from the thigh-bone the angle at




166      SKELETON OF THE RHINOCEROS.
which they are therein inserted becomes more favorable
for their force; the longer, therefore, and the more horizontal the pelvis, the better the hind-quarter of the horse,
and its qualities for swiftness and maintenance of speed
depend much on the "good point" due to the development
of this part of the skeleton. The femur, 65, is characterized by a third trochanter springing from the outer part
of the shaft before the great trochanter. There is a splintshaped rudiment of the proximal end of the fibula, 67,
but not any rudiment of the distal end. The tibia, 66, is
the chief bone of the leg. The heel-bone, "calcaneum,"
is much produced, and forms what is called the " hock."
The astragalus is characterized by the depth and obliquity
of the superior trochlea, and by the extensive and undivided anterior surface, which is almost entirely appropriated by the naviculare. The external cuneiforme is
the largest of the second series of tarsals, being in proportion to the metatarsal of the large middle digit, iii,
which it mainly supports. The diminished cuboides articulates partly with this, partly with the rudiment of the
metatarsal corresponding with that of the fourth toe, iv.
A similar rudiment of the metatarsal of the toe, corresponding with that of the second, ii; articulates with a
cuneiforme medium —here, however, the innermost of the
second series of tarsal bones.
Of all the other known existing hoofed quadrupeds, it
would hardly be anticipated that the rhinoceros presented
the nearest affinity to the horse; one might rather look to
the light camel or dromedary; but a different modification
of the entire skeleton may be traced in the animals with
toes in even number, as compared with the horse and other
odd-toed hoofed quadrupeds. In an extinct kind of horse
(tIippopotherium), the two splint-bones are more developed,




SKELETON OF THE RHINOCEROS.             167
and each supports three phalanges, the last being provided
with a diminutive hoof. In the extinct Palteotheria, the
outer and inner digits acquired stronger proportions, and
Fig. 29.
S  L 
65
6/  a 6
SKELETON OF THE RHINOCEROS (Rh. bicorni8).
the entire foot was shortened. The transition from the
Palceotheria, by the extinct hornless rhinoceros (Acerotherium), to the existing forms of rhinoceros, is completed.
In the skeleton of the rhinoceros, we find resemblances to
the horse in the number of the dorsal vertebrae, in the
third trochanter of the femur, and in the number of digits
on each foot, albeit the two that are hidden and rudimental in the swifter quadruped are here made manifest in
their full development: the concomitant shortening of the
whole foot, and strengthening of the entire limbs, accord
with the greater weight of the body to be supported, clad
as it is with a coat-armor of thickened tuberculated hide:
the broader feet, terminated each by three hoofs, afford a
better basis of support in the swampy localities affected




168      SKELETON OF THE RHINOCEROS.
by the rhinoceros. Both scapule and iliac bones are of
greater breadth, and less length. The ulna is fully developed in the fore-limb, and the fibula in the hind-leg;
but there is no power of rotation of the fore-limb in any
hoofed quadruped. The upper surface of the skull is
roughened for the attachment of the horn, and in two
distinct places where the species has two horns.
If the equine skull be compared with that of the rhinoceros, the basioccipital will be seen to be narrow and
more convex. The true mastoid intervenes, as a tuberous
process, between the post-tympanic and paroccipital process, clearly indicating the true nature of the post-tympanic in the rhinoceros; the tapir shows an intermediate
condition of the mastoid between the rhinoceros and
horse. The latter differs from both the tapir and rhinoceros in the outward production of the sharp roof of
the orbit and the completion of the bony frame of that
cavity behind by the junction of the postorbital process
with the zygoma. The temporal fossa, so defined, is small
in proportion to the length of the skull: the base of the
postorbital process is perforated by a superorbital foramen. The lachrymal canal begins by a single foramen.
The premaxillaries extend to the nasals, and shut out
the maxillaries from the anterior aperture of the nostrils. The chief marks of affinity to other odd-toed
hoofed beasts (Perissodactyles) are seen in the shape, size,
and formation of the posterior aperture of the nostrils,
the major part of which is bounded by the palatine bones,
of which only a small portion enters into the formation
of the bony palace, which terminates behind opposite the
interspace between the penultimate and last molars. A
narrow groove divides the palato-pterygoid process from
the socket of the last molar, as in the tapir and rhinoceros.
The pterygoid process has but little antero-posterior ex



CHARACTERS OF ODD-TOED HOOFED BEASTS. 169
tent: its base is perforated by the ectocarotid canal. The
entopterygoids are thin plates, applied like splints over
the inner side of the squamous suture between the pterygoid processes of the palatines and alisphenoids. The
postglenoid process in the horse is less developed than in
the tapir. The Eustachian process is long and styliform.
There is an anterior condyloid foramen, and a wide
"fissura lacera."  The broad and convex bases of the
nasals articulate with the frontals a little behind the anterior boundary of the orbits. The space between the
incisors and molars is of greater extent than in the tapir;
a long diastema is not, however, peculiar to the horse;
and, although it allows the application of the bit, that
application depends rather upon the general nature of the
horse, and its consequent susceptibility to be broken in,
than upon a particular structure which it possesses in
common with the ruminants and some other herbivora.
The tapir and the rock cony have four digits on each
fore-foot, and three digits on each hind-foot; but they
resemble more the horse and rhinoceros than any other
Ungulata.  If the osteological characters of the hoofed
animals with the hind digits in uneven number be compared together, they will be found to present, notwithstanding the differences of form, proportion, and size
presented by the rhinoceros, hyrax, tapir, and horse, the
following points of agreement, which are the more significative of natural affinity when contrasted with the
skeletons of the hoofed animals with digits in even number. Thus, in the odd-toed or " perissodactyle" ungulates,
the dorso-lumbar vertebrae differ in different species, but
are never fewer than twenty-two; the femur has a third
trochanter, and the medullary artery does not penetrate
the fore part of its shaft. The fore part of the astragalus
15




170         SKELETON OF THE GIRAFFE.
is divided into two very unequal facets. The os magnum
and the digitus medius which it supports is large, in some
disproportionately, and the digit is symmetrical; the
Fig. 30.
6.8
56
SKELETON OF THE GIRAFFE (Camelopardalis giraffa).
same applies to the ectocuneiform and the digit it sup.
ports in the hind foot. If the species be horned, the horn
is single; or if there be two, they are placed on the me



SKELETON OF THE GIRAFFE.            171
dian line of the head, one behind the other, each being
thus a single or odd horn. There is a well-developed
post-tympanic process, which is separated by the true
mastoid from the paroccipital in the horse, but unites
with the lower part of the paroccipital in the tapir, and
seems to take the place of the mastoid in the rhinoceros
and hyrax. The hinder half, or a larger proportion, of
the palatines enters into the formation of the posterior
nares, the oblique aperture of which commences in advance of the last molar, and, in most, of the penultimate
one. The pterygoid process has a broad and thick base,
and is perforated lengthwise by the ectocarotid. The
crowns of the antepenultimate, as well as the penultimate
and last premolars, are as complex as those of the molars;
that of the last lower milk-molar is bilobed. To these
osteological and dental characters may be added some
important modifications of internal structure, as, e. g., the
simple form of the stomach, and the capacious and sacculated czecum, equally indicating the mutual affinities of
the odd-toed or perissodactyle hoofed quadrupeds, and
their claims to be regarded as a natural group of the
Ungulata. Many extinct genera, e. g., lophiodon, tapiotherium, palheotherium, hippotherium, acerotherium, macrauchenia, elasmotherium, coryphodon, have been discovered, which once linked together the now broken
series of Perissodactyla, represented by the existing
genera rhinoceros, hyrax, tapyrus, and equus.
Another series of hoofed quadrupeds is characterized
by having their hoofs and digits in even number in both
fore and hind feet. The majority of these have a pair, so
developed as to serve as feet, and terminated by a pair of
hoofs so shaped as to look like one split hoof, whence the
name "cloven-footed," given to this predominant family of




172 CHARACTERS OF EVEN-TOED HOOFED BEASTS.
"artiodactyle," or even-toed beasts; the synonym "ruminant," indicative of the same great family, is deduced from
the characteristic complexity of their act of digestion.
No food is more remote or distinct from flesh than grass.
Extremities enveloped in hoofs are incapacitated from
seizing and retaining a living prey, hence all hoofed
mammals are necessarily herbivorous: hence the c6mplexity of their grinding teeth, the concomitant strength
of their grinding muscles, and weakness of the biting
muscles; the length of the neck, to enable the head to
reach the verdant earth, and the length and slenderness
of the jaws. The absence of a clavicle, and of any power
of rotating the bones of fore-leg and fore-foot, are also constant characteristics of both great divisions of the Ungulata
or hoofed quadrupeds.
The ox, the hog, and the hippopotamus are examples
of even-toed hoofed quadrupeds. In the ox, besides the
two large and normally developed hoofs, two small supplementary hoofs dangle behind, in each foot; in the hog
these are brought down to the level of the midpair, but
are smaller; in the hippopotamus the four digits and hoofs
are subequal on each foot. From this type of extremity
to that of the giraffe, or camel, where the digits are absolutely restricted to two on each foot, there is a close series
of gradational shortcomings affecting the outer and the
inner toes, until they wholly disappear. The giraffe (Fig.
30) is a ruminant dwelling in climes where herbage disappears from the parched soil soon after the rainy season
has terminated, and where sustenance for a herbivore of
its bulk could hardly be afforded, except by trees: it is
therefore modified to browse on the tender branches, and
chiefly of the light and lofty acacias. Its trunk is accordingly short, and raised high upon long and slender limbs,




CHARACTERS OF EVEN-TOED HOOFED BEASTS. 173
especially at the forepart; a small and delicate head is
supported on an unusually long neck. The number of
vertebrae here, however, accords with that characteristic
of the mammalian class, viz: seven. They are peculiar
for the length of their bodies. There are fourteen dorsal
vertebrae with very long spinous processes, and supporting long and slender ribs, especially the anterior ones,
seven pairs of which join the sternum, which consists of
six bones; the lumbar vertebrae are five in number, the
sacral four, and the caudal twenty; this series is terminated in the living animal by a tuft of long, wavy, stiff
black hair, forming an admirable whisk to drive off insect
tormentors. The bladebone, 51, is remarkably long and
slender; its spine or ridge forms a very low angle, and
gradually subsides as it approaches the neck of the scapula; the coalesced coracoid is a large tuberosity. The
humerus, 53, forms the shortest of the three segments of
the limb; it is remarkable for the strength of the proximal
processes; the second segment is chiefly constituted, as in
all ruminants, by the radius, 55; the slender shaft of the
ulna, 56, which supports a long olecranon, becomes blended
with the radius, and lost at its lower third, but its distal
end reappears as a distinct part. The metacarpals of the
retained digits, answering to the third and fourth in the
human and other five-fingered (pentadactyle) hands, are
blended together to form a single " cannon.bone" of the
veterinarians; but the nature of this is different from that
in the horse; it divides at its distal end into two wellformed trochleve, or pulley-joints, and to these are articulated the digits iii and iv, which each consist of three joints
or phalanges. Thus the main extent of this singularly
elongated limb is gained by the excessive development of
the band-segment, restricted, however, to those elements
15*




174 CHARACTERS OF IIERBIVOROUS QUADRUPEDS.
that answer to the middle and ring-fingers of the human
hand.
The pelvis, of which the sacral, S, iliac, 62, and ischial,
64, elements are shown in Cut 31, is small in proportion
to the animal's bulk. The femur, 65, is short like the
humerus, and chiefly remarkable for the great expanse of
this distal end. The tibia, 66, forms the main basis of the
leg, as its homotype the radius does in the forearm, but
the fibula is more reduced than in the ulna; rarely in any
ruminant is more of it visible than its distal end, 67,
wedged in between the tibia and the calcaneum. The
series of tarsal bones, 68, is peculiar in all ruminants for
a coalescence of the two bones answering to the " scaphoid
and cuboid" in the human tarsus. In all ruminants the
astragalus is unusually symmetrical in shape, with a deep
trochlear articular surface for the tibia, and two equal
convex surfaces for succeeding tarsal bones; the calcaneum is produce* into a long " hock."  The rest of the
bones of the hind-foot conform closely with those of the
fore-foot.
A few remarks, although interesting chiefly to the professed anatomist, appear called for in reference to the bony
structure of the head of the giraffe.
The exoccipitals form a marked protuberance above
the foramen magnum, and below a deep fossa, for the implantation of the ligamnenturn nuchbe-the length of the
dorsal spines being related, in all ruminants, to a due
surface for the attachment of this strong elastic support
of the head and neck. The parietals are chiefly situated
on the upper surface of the skull; the osseous horn-cores,
which are originally distinct, become anchylosed in old
giraffes, across the coronal suture, equally to the parietals
and frontals: if one of these be divided longitudinally, it




SKELETON OF THE CAMEL.               175
will show the extension of the frontal and parietal sinuses
into its lower fourth, the rest of the horneore being a solid
and dense bone. The protuberance upon the frontal and
contiguous parts of the nasal bones is entirely due to an
enlargement of those bones, and not to any distinct osseous part: its surface is roughened by vascular impressions.
The lachrymal is separated from the nasal by a large vacuity intervening between those bones, the frontal and
the maxillary. The premaxillaries, which are of unusual
length, articulate with the nasals. The petrotympanic is
a separate bone, as in all ruminants.  The symphysis of
the lower jaw is unusually long and slender in the giraffe.
In the skeleton of the Camel (Camelus bactrianus) the
vertebral formula is-seven cervical, twelve dorsal, seven
lumbar, four sacral, eighteen caudal. Seven pairs of ribs
articulate directly with the sternum, which consists of six
bones, the last being greatly expanded and protuberant
below, where it supports the pectoral callosity in the living
animal. The cervical region, though less remarkable for
its length than in the giraffe, is longer than in ordinary
ruminants, and is remarkable for its flexuosity; the vertebroe are peculiar for the absence of the perforation for
the vertebral artery in the transverse process, with the
exception of the atlas; that artery, in the succeeding cervicals, enters the back part of the neural canal, and perforates obliquely the forepart of the base of the neurapophysis. The costal part of the transverse process is large
and lamelliform in the fourth to the sixth cervical vertebrme
inclusive: in the seventh it is a short protuberance. The
spinous process of the first dorsal suddenly exceeds in
length that of the last cervical, and increases in length to
the third dorsal; from this to the twelfth dorsal the summits of the spines are on almost the same horizontal line,




1'76        SKELETON OF THE CAMEL.
and are expanded and obtuse above, sustaining the substance of the two humps of this species; they afford,
however, no other indication of those risings, which are
as independent of the osseous system as is the dorsal fin
in the grampus or porpoise. The spines of the lumbar
vertebrae progressively decrease in length. The spine of
the scapula is produced into a short-pointed acromion:
the coracoid tubercle is large, and grooved below. The
ridge upon the outer condyle of the humerus is much less
marked than in the normal ruminants. The ulna has
coalesced more completely with the radius, and appears
to be represented only by its proximal and distal extremities. The carpal bones have the same number and
arrangement as in ordinary ruminants, but the pisiforme
is proportionally larger. There is no trace of the digits
answering to the first, second, and fifth in the pentadactyle
foot: the metacarpals of those answering to the third and
fourth have coalesced to near their distal extremities,
which diverge more than in the ordinary ruminants,
giving a greater spread to the foot, which is supported by
the ordinary three phalanges of each of those digits. The
last phalanx deviates most from the form of that in the
ordinary ruminants by its smaller proportional size,
rougher surface, and less regular form: it supports, in
fact, a modified claw rather than a hoof. In the femur
the chief deviation from the ordinary ruminant type is
seen in the position of the orifice of the canal for the medullary artery, which, as in the human skeleton, enters
the back part of the middle of the shaft, and inclines
obliquely upwards. The fibula is represented by the
irregularly-shaped ossicle interlocked between the outer
side of the distal end of the tibia and the calcaneum. The
scaphoid is not confluent with the cuboid as in the normal




SKELETON OF THE CAMEL.              177
ruminant: the rest of the hind-foot deviates in the same
manner and degree from the ordinary ruminant type, as
does the fore-foot.
The camel tribe have no horns; some small deer of
the musk-family are compensated for the want of horns
by very long and sharp upper canine teeth; the rest of
the ruminants, either in the male sex- or in both sexes,
are endowed with the weapons of offence and defence,
developed from and supported by the head, called "horns"
and " antlers."  The term " horn" is technically restricted
to the weapon which is composed of a bony base, covered
by a sheath of true horny matter. Such horns are never
shed; and as, in order to diminish the weight of the head,
the horn-core is made as hollow as is consistent with
strength, the ruminants with such horns are called hollowhorned; the ox, the sheep, and the antelope are examples.
Antlers consist of bone only. During the period of their
growth they are covered by a vascular, short-haired skin
like velvet; but when their growth is completed, this
skin dries and peels off, leaving the antler a solid, naked,
and insensible weapon. Being deprived, however, of its
vascular support it dies, and, after a certain period of service, is undermined by the absorbents and cast off. The
process of growth and decadence of the antlers is repeated each year; and in the fallow-deer the antlers progressively acquire greater size and more branches to the
sixth year, when the animal is in its prime. Good evidence has been obtained that the same law of growth,
shedding, and annual renewal prevailed in the gigantic
fossil deer of Ireland, in which upwards of eighty pounds
of osseous matter must have been developed from the
frontal bones every year in the full-grown animal. The
ruminants of the deer and elk tribes are those which have




178   SKELETON OF THE HIPPOPOTAMUS.
antlers, or are "solid-horned."  The horns of the giraffe
are peculiar; they are short and simple, are always
covered by a hairy integument, and are never shed.
They relate in position to both the frontal and parietal
bones. In all other ruminants, the horns are developed
from the frontals exclusively, although they sometimes,
-as in the ox, project from the back part of the cranium;
but the frontals, in such cases, extend to that part. The
horn of the rhinoceros consists wholly of fibrous horny
matter.
The even-toed hoofed animals that do not ruminate
have no horns. The osteology of this division is here
illustrated in the hippopotamus (Fig. 31). The skeleton,
Fig. 31.
SKELETON OF THE HIPPOPOTAMUS AMPHIBIUS.
in its strength and massiveness, presents a greater contrast with that of the giraffe than the rhinoceros's skeleton
does with that of the horse; there are, nevertheless, as
will be shown in the concluding summary, more essential
points of resemblance to the giraffe's skeleton than to




SKULL OF THE HIPPOPOTAMUS.            179
that of the rliinoceros. In points of minor importance,
we find the hippopotamus resembling the rhinoceros; as
e. g. in the shortness and strength of its neck; but it has
only fifteen dorsal, d, and four lumbar, 1, vertebra. The
spines of these vertebrae are shorter and less unequal
than in the ruminants; and they have an almost uniform
direction, as in all quadrupeds that do not move by leaps
or bounds. The tail is short, and, in the living animal,
compressed, acting like a rudder. The bones of the
limbs are short and thick. In the scapula, 51, the acromion is slightly produced, and the coracoid recurved.
The great tuberosity of the humerus, 53, is divided into
two subequal processes.  The ulna and radius have
coalesced at their extremities, and at the middle of their
shaft, the interosseous space being indicated by a deep
groove and two holes. In the carpal series of bones, the
trapezium is present, but does not support any digit; the
innermost, answering to the thumb or pollex, therefore,
is the one which is absent; of the remaining four digits,
the two middle ones, answering to the third and fourth,
are most developed. The femur has no third trochanter.
The fibula is distinct from the radius, and-extends from
its proximal end to the calcaneum. The entocuneiform
bone is present in the tarsus, but there is no rudiment of
the innermost toe or hallux; the proportions of the other
four toes resemble those on the fore-foot.
The skull is remarkable for the prominence and high
position of the orbits, which allow the eye to be projected
above the surface of the water, and a survey to be made
by the suspicious animal without the exposure of any
other part of the head. The upper jaw is peculiar for
the development of the sockets of the great canine teeth,




180   CHARACTERS OF EVEN-TOED BEASTS.
and the lower jaw combines with the -like character an
unusual production and curvature of the angle.
With regard to the osteology of the hog tribe, our
limits compel us to restrict ourselves to the notice of the
still more singular development of the sockets of the upper canines or tusks in the babyroussa, in which those
teeth curve upwards and pierce the skin of the face, like
horns, whence the name "horned hog" sometimes imposed upon it.
If the hoofed animals with the digits in even number
be compared together, in regard to their osteological characters, they will be found, notwithstanding the difference
of form, proportion, and size presented by the hippopotamus, wild boar, xvieugna, and chevrotain, to agree in
the following points, which are the more significative of
natural affinity when contrasted with the skeletons of the
hoofed animals with digits in uneven number. Thus, in
the even-toed or "artiodactyle" ungulates, the dorso-lumbar vertebrae are the same in number, as a general rule,
in all the species, being nineteen. The rare exceptions
appear to be due to the development, rarely to the suppression, of an accessory vertebra as an individual variety, the number in such cases not exceeding twenty, or
falling below eighteen, and the supernumerary vertebra
being most usually manifested in the domesticated and
highly-fed breeds of the common hog. The recognition
of this important character appears to have been impeded
by the variable number of movable ribs in different qpecies of the artiodactyles, the dorsal vertebrae, which these
ribs characterize, being fifteen in the hippopotamus and
twelve in the camel; and the value of this distinction has
been exaggerated owing to the common conception of
the ribs as special bones, distinct from the vertebrae, and




CHARACTERS OF EVEN-TOED BEASTS.   181
their non-recognition as parts of vertebra equivalent
to the neurapophyses and other autogenous elements.
The discovery of the pleurapophyses under the condition
of rudimental ribs attached to the ends of the lumbar diapophyses, which afterwards become suturally attached or
anchylosed, and the pleurapophysial nature of a part of
the so-called perforated transverse process of the cervical
vertebra, show that the anthropotomical definition of a
dorsal vertebra, as one that supports ribs, is inapplicable
to the mammalia generally, and is essentially incorrect.
It is convenient, in comparative tables of vertebral formulse, to denote the number of those vertebrae of the trunk
in which the pleurapophyses remain free and movable, constituting the "ribs" of anthropotomy; but the differences
sometimes occurring in this respect, in individuals of the
same species, have their unimportance manifested when the
true nature of a rib is recognized. The vertebral formulse of the artiodactyle skeletons show that the difference
in the number of the so-called dorsal and lumbar vertebrae does not affect the number of the entire dorso-lumbar
series: thus, the Indian wild boar has d, 13, 1, 6 = 19;. e. 13 dorsal, and 6 lumbar, making a total of 19 trunkvertebrse; the domestic hog and the peccari have d, 14,
1, 5, = 19; the hippopotamus has d, 15, 1,4, = 19; the gnu
and aurochs have d, 14, 1, 5, = 19; the ox, and most of
the true ruminants, have d, 13, 1, 6, = 19; the camel and
lamas have d, 12, 1 7, 7,- 19. These facts illustrate the
natural character and true affinities of the artiodactyle
group. They are further shown by the absence of the
third trochanter in the femur, and by the place of perforation of the medullary artery at the fore and upper part
of the shaft, as in the hippopotamus, the hog, and most
of the ruminants. The fore part of the astragalus is di16




182   CHARACTERS OF EVEN-TOED BEASTS.
vided into two equal or subequal facets; the os magnum does not exceed, or is less than, the unciforme in
size, in the carpus; and the ectocuneiforme is less, or
not larger, than the cuboid, in the tarsus. The digit
answering to the third in the pentadactyle foot is unsymmetrical, and forms, with that answering to the
fourth, a symmetrical pair. If the species be horned,
the horns form one pair or two pairs; they are never developed singly and symmetrically from the median line.
The post-tympanic does not project downward distinctly
from the mastoid, nor supersede it in any artiodactyle;
and the paroccipital always exceeds both in length. The
bony palate extends further back than in the perissodactyles; the hinder aperture of the nasal passages is more
vertical, and commences posterior to the last molar tooth.
The base of the pterygoid process is not perforated by
the ectocarotid artery. The crowns of the premolars are
smaller and less complex than those of the true molars,
usually representing half of such crown. The last milkmolar is trilobed.
To these osteological and dental characters may be
added some important modifications of internal structure,
as e. g. the complex form of the stomach in the hippopotamus, peccari, and ruminants, the comparatively small
and simple caecum, and the spirally folded colon, which
equally indicate the mutual affinities of the even-toed or
artiodactyle hoofed quadrupeds, and their claims to be
-regarded as a natural group of the Ungulata. Many extinct genera, e. g. chmeropotamus, anthracotherium, hyopotamus, dichodon, merycopotamus, xiphodon, dichobune,
anoplotherium, have been discovered, which once linked
together the now broken series of Artiodactyla, represented by the existing genera hippopotamus, sus, dico



THE NATURE OF LIMBS.                183
tyles, camelus, moschus, camelopardalis, cervus, antelope,
ovis, and bos.
As we have now traced both the fore and hind foot to
the five-toed or pentadactyle structure, with the definite
number of joints or phalanges in each toe, characteristic
of the highest class of vertebrate animals, a few remarks
will be offered in illustration of the plan of structure
which prevails in such extremities, and of the law that
governs the departure from the pentadactyle type in the
n ammalia.
The essential nature of the limbs is best illustrated by
the fish called protopterus, and by some of the lower
reptiles that retain gills with lungs.
If the segment of the skeleton supporting the rudiments of the fore-limbs in the protopterus (Fig. 32), be
Fig. 32.
PROTOPTERUS.
compared with the modification of the typical vertebra,
exemplified in Fig. 6, p. 28, it will be seen to be constructed on the same type.  The hiemal arch is most expanded, and it is composed of a pleurapophysis or vertebral rib, pl, and a hoemapophysis or sternal rib, h, on
each side; the hyemal spine, or sternum, is not here developed; the long, many-jointed ray, a, answers to the
more simple diverging appendage, a, in Fig. 5.




184          THIE NATURE OF LIMBS.
The segment supporting these appendages, or first
rudiments of the fore-limb in the fish, is the occipital
one, or the last vertebra of the skull. The pleurapophysis of this segment is the seat of all those modifieations which have earned for it the special name of
" scapula," 51; the hbemapophysis is the seat of those
that have led to its being called "coraeoid," 52.
The corresponding segment of the batrachian amphiurma (Fig. 33) yields the next important modification of
these parts. The scapule, pl, 51, are detached from the
occiput, or neutral arch; the coracoids, h, 52, are much
expanded; three segments of the diverging appendage, a,
are ossified, and two of these segments are bifid, showing
Fig. 33.                  Fig. 34.
A                        C
AMPHIUMA.                  PROTEUS.
the beginning of the radiating multiplication of its parts.
The first segment is the seat of those modifications which
have obtained for it the special name of "humerus," 53;
the two divisions of the next segment of the appendage are
called "ulna," 53, and "radius," 54; the remainder of the
limb is called "manus," or hand; 56 is the gristly carpus,
and the two bony divisions are the digits or fingers, 57.
The segment supporting the hind-limbs retains most
of its typical character in the subterranean reptile called
the Proteus; one sees, e. g. in Fig. 34, that the centrum
has coalesced with the neurapophyses, n, and neural
spine, nzs, forming the neural arch from which the dia



LAW OF SIMPLIFICATION OF FEET.             185
pophyses, d, are developed: the more expanded haemal
arch consists of the pleurapophyses, pl, and the hsemapophyses, h; the former is called the "ilium," 62, the latter
the "ischium," 63; and, as the hluemapophyses of another
segment are usually added to the scapular arch, when
they receive the name of "clavicles," so also the haemapophyses of a contiguous segment are usually added to
the pelvic arch, when they are called "pubic bones."
The pelvic diverging appendage, a a, has advanced to
the same stage of complexity in the proteus, as the scapular one in the amphiuma; the first ossified segment is
called "femur," 65; the divisions of the next segment
are respectively termed " tibia," 66, and "fibula," 67; the
first set of short bones in the "pes," or foot, are called
"tarsals," 68; those of the two toes are called " metatarsals" and "phalanges," 69.
The tarsal bones, from the degree of constancy of their
forms and relative positions, have received distinct names. In Fig. 35 of Fig. 385. Fig 36.
the bones of the hind-foot in the horse, d
a marks the "astragalus," cl, the "cal-  
caneum, or heel-bone, the prominent
part of which forms the "hock;" s is the    a.
"scaphoides," or naviculare, b, the " cu-   i 
boid," cc, "ectocuneiform," and cm, the
"mnesocuneiform." Now, the ectocuneiform in all mammalia supports the third
or middle of the five toes when they
are all present, the mesocuneiform supports the second toe, and the cuboides'the fourth and fifth. We see, therefore,
in the horse, that the very large bone    q'       m
articulated to the ectocuneiform, ce, is  MORSE.   oX.
16*




186    LAW  OF SIMPLIFICATION  OF FEET.
the metatarsal of the third toe, to which are articulated the
three phalanges of the same toe, iii, the last phalanx being
expanded to sustain the hoof. The small bone called
"split-bone," by veterinarians, articulated to the "mesocuneiform," is the stunted metatarsal of the second toe, ii;
the outer "splint-bone," articulated to the " cuboides," is
the similarly stunted metatarsal of the fourth toe, iv.
In the foot of the ox (Fig. 36), the cuboides, b, presents
a marked increase of size, equalling the ectocuneiform, cc,
which is proportionally diminished. The single bone,
called "cannon-bone," which articulates with both these
carpal bones, does not answer to the single "cannonbone" in the horse, but to the metatarsals of both the
third and the fourth digits; it is accordingly found to
consist of those two distinct bones in the foetal ruminant, and there are a few species in which that distinction
is retained. Marks of the primitive division are always
perceptible, especially at its lower end, where there
are two distinct joints or condyles, for the phalanges
of the third, iii, and fourth, iv, toes. In the horse, the
rudiments of the two stunted toes were their upper ends
or metatarsal bones; in the ox, they consist of their lower
ends or phalanges; these form the " spurious hoofs," and
are parts of the second, ii, and fifth, v, toes (Fig. 36). The
rhinoceros more closely resembles the horse in the bony
structure of its hind-foot (Fig. 37); the ectocuneiform is
still the largest of the three lowest tarsal bones, although
the mesocuneiform, cm, and the cuboids, b, have gained
increased dimensions in accordance with the completely
developed toes which they support; these toes we therefore recognize as being answerable to the rudiments of
the second, ii, and fourth, iv, in the horse, the principal
toe being still the third, iii. The hippopotamus (Fig. 38)
chiefly differs from the ox, as the rhinoceros differs from




LAW OF SIMPLIFICATION  OF FEET.             187
the horse, viz: by manifesting the two toes fully developed, which were rudimental in the more simple foot;
the cuboides, b, being proportionally extended to support
the fifth toe, v, as well as the fourth, iv; the second toe,
ii, articulates, as usual, with a distinct tarsal bone. In
the elephant (Fig. 39), where a fifth digit is added,
Fig. 37.       Fig. 38.        Fig. 39.
RHlINOCEROS.   HIPPOPOTAMUS.    ELEPHANT.
answering to our first or great toe, I, there is also a distinct carpal bone, called the "entocuneiform," ci, and the
tarsus presents, as in other pentadactyle mammals, all the
bones which are seen in the human tarsus, viz: the
astragalus, a, the calcaneum, c, the scaphoides, s, the entocuneiform, ci, the mesocuneiform, cm, the ectocuneiform,
cc, and the cuboides, b.
The course of the simplification of the pentadactyle
foot or hand is first a diminution and removal of the
innermost digit, i; next of the outermost, v; then of the
second, ii; and lastly of the fourth, iv; the third or middle
toe, iii, being the most constant and important of the five
toes.  The same law or progress of simplification prevails
in the fore-foot or hand. The thumb is the first to disappear, then the little finger, and the middle finger is the




188         SKELETON OF THE SLOTH.
most constant, and forms the single-hoofed fore-foot of
the horse.
The scapula, 51, in the fore-limb repeats or answers to
the ilium, 62, in the hind-limb; the coracoid, 52, to the
ischium, 63; the clavicle, 58, to the pubis, 64; the humerus, 53, to the femur, 65; the radius, 55, to the tibia,
66; the ulna, 54, to the fibula, 67; the carpus, 56, repeats
the tarsus, 68; and the metacarpus and phalanges of the
fore-foot repeat the metatarsus and phalanges of the hindfoot: they are technically called "serial homologues," or
" homotypes," and each bone in the carpus can be shown
to have its homotypbe in the tarsus. (See Archetype of the
T'ertebrate Skeleton," p. 167.)
SKELETON OF TIHE SLOTH.
The transition from the quadrupeds with hoofs to those
with claws seems in the present series to be abrupt; but
it was made gradual by a group of animals, now extinct,
which combined hoofs and claws in the same foot. Some
of the outer toes, at least, were stunted and buried in a
thick callosity, for the ordinary purpose of walking,
whilst the other toes were provided with very long and
strong claws for uprooting or tearing off the branches of
trees. These singular beasts were of great bulk, and appear to have been peculiar to America. As restored by
anatomical science, they have received the names of Megatheriurn, iMegalonyx, Mylodon, &c. They were huge terrestrial sloths; the preseit remnants of the family consist
of very few species enabled by their restricted bulk to
climb the trees in quest of their leafy food, and peculiarly
organized for arboreal life. The toes, which were modi



SKELETON OF THIE SLOTH.              189
fled in their huge predecessors to tread the ground, are
reduced to rudiments, or are undeveloped; and those only
are retained which support the claws, now rendered by their
length and curvature admirable instruments for clinging
to the branches. The whole structure of the hind and
fore limbs is modified to give full effect to these instruments as movers and suspenders of the body'in the bosky
retreats for which the sloths are destined; and, in the
same degree, the power of the limbs to support and carry
the animal along the bare ground is abrogated. Accordingly, when a sloth is placed on level ground, it presents
the aspect of the most helpless and crippled of creatures.
It is less able to raise its trunk above its limbs than the
seal, and can only progress by availing itself of some inequality in the soil offering a holdfast to its claws, and
enabling it to drag itself along. But to judge of the
creative dispensations towards such an animal by observation of it, or reports of its procedure, under these
unnatural circumstances, would be as reasonable as a speculation on the natural powers of a tailor suddenly transferred from his shopboard to the rigging of a ship under
way, or of a thorough-bred seaman mounted for the first
time on a full-blood horse at Ascot. Rouse the prostrate
sloth, and let it hook on to the lower bough of a tree, and
the comparative agility with which it mounts to the topmost branches will surprise the spectator. In its native
South American woods its agility is still more remarkable,
when the trees are agitated by a storm. At that time, the
instinct of the sloth teaches it that the migration from tree
to tree will be most facilitated. Swinging to and fro,
back downwards, as is its habitual position, at the end of
a branch just strong enough to support the animal, it
takes advantage of the first branch of the adjoining tree




190          SKELETON OF THE SLOTH.
that may be swayed by the blast within its reach, and
stretching out its fore-limb, it hooks itself on, and at once
transfers itself to what is equivalent to a fresh pasture.
The story of the sloth voluntarily dropping to the ground,
and crawling under pressure of starvation to another tree,
is one of the fabulous excrescences of a credulous and
gossiping zoology.
In the sloth, accordingly (Fig. 40), the fore-limbs are
much elongated, and that less at the expense of the hand
than of the arm and forearm.  The humerus, ~3, is of
Fig. 40.
68
SKELETON OF THE SLOTH.
unwonted length-is slender and straight; the radius, 55,
and ulna, 54, are of similar proportions-the former
straight, the latter so bent as to leave a wide interosseous




APTITUDES OF THE SLOTH.               191
space. Now, moreover, these bones, instead of being
firmly united as one bone, are so articulated with each
other as to permit a reciprocal rotatory movement, chiefly
performed, however, by the radius; and since to this bone
the carpal segment of the hand is mainly articulated, that
prehensile member can be turned prone or supine, as in
the human arm and hand. Six bones are preserved in
the carpus of three-toed sloth (Bradypus tridactylus), answering to those called "lunare," "-cuneiforme," "unciforme," and "pisiforme," also to the "scaphoides and
trapezium" united, and to the " trapezoides and magnum"
united. The scapho-trapezium is characteristic of the
sloth-tribe, and is found in the extinct as well as existing
species. The articulation of the carpus with the radius,
and with the metacarpus, is such as to turn the palm of
the long hand inwards, and bring its outer edge to the
ground. The three fully-developed metacarpals are confluent at their base, which is also anchylosed to the rudiinents of the first and fifth metacarpals; the proximal
phalanges of the digits answering to ii, iii, and iv, are
confluent with their metacarpals, and those digits appear
therefore to have only two joints. The last phalanx is
remarkably modified for the attachment of the very long
and strong claw.
With regard to the bladebone of the sloth, 51, it is
much broader in proportion to its length than in the swift
cloven-footed herbivores; the spinous process is unusually short; the acromion is of moderate length, and unexpanded at its extremity; the supraspinal fossa is the
broadest, and has a perforation instead of the usual " supraspinal" notch. There is a short clavicular bone
attached to the acromion, but not attaining to the sternum.




192           LIMBS OF THE SLOTH.
The iliac bones, 62, repeat the modifications of their
homotypes the scapulse, and are of unusual breadth as
compared with those of other quadrupeds; they soon become anchylosed to the broad sacrum, S, the ischia, 63,
and pubes, 64, are long and slender, and circumscribe
unusually large "thyroid" and "ischial" foramina, the
latter being completed by the coalescence of the tuberosities of the ischia with the transverse processes of the last
two sacral vertebrae. The head of the femur, 65, has no
impression of a ligamentum teres. The patella, 66', is
ossified; there is a fabella behind the external condyle.
The tibia, 66, and fibula, 67, are bent in opposite directions, intercepting a very wide interosseous space. The
anchylosis of their two extremities, which has been found
in older specimens, has not taken place here. The inner
malleolus projects backwards and supports a grooved
process. The outer malleolus projects downwards, and
fits like a pivot into a socket in the astragalus, turning
the sole of the foot inwards-a position like that of the
hand-best adapted for grasping boughs. The calcaneum,
68, is remarkably long and compressed. The scaphoid,
cuboid, and cuneiform bones have become confluent with
each other and the metatarsals, of which the first and fifth
exist only in rudiment. The other three have likewise
coalesced with the proximal phalanges of the toes which
they support: these toes answer to the second, third, and
fourth, in the human foot.
The short and small head of the sloth is supported on
a long and flexible neck presenting the very unusual character in the Mammalian class of nine vertebrae, C-the
superadded two, however, appearing to have been impressed from the dorsal series, D, by their short, pointed,
and usually movable ribs. The head and mouth can




SKULL OF TIIE SLOThI.             193
be turned round every part of a branch in quest of the
leafy food by this mechanism of the neck. As the trunk
is commonly suspended from the limbs with the back
downwards, the muscles destined for the movements of
the back and support of the head are feebly developed,
and the vertebral processes for their attachment are proportionally short. The spines of the neck-vertebrae are
of more equal length than in most mammals-that of the
dentata being little larger than the rest: the spines gradually subside in the posterior dorsals, and become
obsolete in the lumbar vertebrae. The first pair of fullydeveloped ribs, marking the beginning of the true " dorsal"
series of vertebrae, are anchylosed to the breast-bone
which consists of eight ossicles. In the two-toed sloth,
however, which has twenty-three dorsal vertebrae, there
are as many as seventeen subcubical sternal bones in one
long row, with their angles truncated for the terminal
articulations of the sternal ribs, which are ossified.
The skull of the sloth is chiefly remarkable for the
size, shape, and connections of the malar bone, which is
freely suspended by its anterior attachment to the maxillary and frontal, and bifurcates behind; one division extending downwards, outside the lower jaw, the oJher
ascending above the free termination of the zygomatic
process of the squamosal. The prernaxillary bone is
single and edentulous, being represented only by its
palatal portion completing the maxillary arch, but not
sending any processes upwards to the nasals.
The skull in the toothless ant-eater chiefly forms a
long, slender, slightly-bent bony sheath for its still longer
and more slender tongue, the main instrument for obtaining its insect food. The mouth in the living animal
is a small orifice at the end of the tubular muzzle, just
17




194          SKELETON OF THE MOLE.
big enough to let the vermiform tongue glide easily in
and out. The fore-limbs are remarkable for the great
size and strength of the claw developed from the middle
digit: this is the instrument by which the ant-eater mainly
effects the breach in the walls of the termite fortresses,
which it habitually besieges in order to prey upon their
inhabitants and constructors. As in the sloths, both fore
and hind feet have an inclination inwards, whereby the
sharp ends of the long claws are prevented from being
worn by that constant application to the ground which
must have resulted from the ordinary position of the foot.
The trunk-vertebra, of the ant-eater are chiefly remarkable for the number of accessory joints by which they
are articulated together. This complex structure is also
met with in the armadillos, in which the anterior zygapophyses of the dorsal vertebra send processes-the metapophyses (Fig. 2, p. 165), m., n —upwards, outwards, and
forwards, which processes, progressively increasing in the
hinder vertebrae, attain, in the lumbar region, a length
equal to that of the spinous processes, ns, and have the
same relation to them, in the support of the osseous carapace, as the "tie-bearers" have to the "king-post" in the
architecture of a roof.
SKELETON  OF TIIE MOLE.
The mole is hardly less fitted for the actions of an ordinary land-quadruped than the sloth; but the one is as
admirably constructed for subterraneous as the other
for arboreal life. The fore-limbs are remarkably short,
broad, and massive in the mole, as they are long and
slender in the sloth; yet the same osseous elements,




SKELETON OF.THE MOLE.                195
similarly disposed, occur in the skeleton of each. The
head of the mole is long and cone-shaped; its broad base
joins on the trunk without any outward appearance of a
neck. The forepart of the trunk, to which the principal
muscular masses working the fore-limbs are attached, is
Fig. 41.
5'
tlG
SKELETON OF TIlE MOLE.
the thickest, and thence the body tapers to the hindquarters, which are supported by limbs as slender as they
are short.
The neck-bones, nevertheless, are not wanting; they
even exist in the same number as in the giraffe; the vertebral formula of the mole being-7 cervical, 13 dorsal,
6 lumbar, 5 sacral, and 10 caudal. The spine of the
second vertebra or dentata is large, and extended back
over the third vertebra: the neural arches of this and the
succeeding neck-vertebrae form thin simple arches without spines: the entire vertebrae have been described as
mere rings of bone; but the transverse processes of the
fourth, fifth, and sixth cervicals are produced forwards
and backwards, and overlap each other: in the seventh
vertebra those processes are reduced to tubercular diapoplyses which are not perforated: the bodies of the verte



196          SKELETON OF THE MOLE.
brae are depressed and quadrate. The part answering to
the nuchal ligament in the giraffe is bony in the mole, u.
The first.sternal bone, or manubrium, is of unusual
length, being much produced forwards, and its under
surface downwards in the shape of a deep keel for extending the origin of the pectoral muscles. Seven pairs
of ribs directly join the sternum, which consists of four
bones, in addition to the manubrium and an ossified ensiform appendage. The neural spines, which are almost
obsolete in the first eight dorsals, rapidly gain length in
the rest, and are antroverted in the last two dorsal vertebrao. The diapophyses, being developed in the posterior
dorsals, determine the nature of the longer homologous
processes in the lumbar vertebrae.
The lumbar spines are low, but of considerable anteroposterior extent: the diapophyses are bent forward in the
last four vertebrae: a small, detached, wedge-shaped hypapophysis is fixed into the lower interspace of the bodies
of the lumbar vertebrae.
The scapula, 51, is very long and narrow, but thick,
and almost three-sided: the common rib-shape is resumed
in this cranial pleurapophysis, as we have seen in the
bird and tortoise. The clavicle, on the other hand, instead of the usual long and slender figure, presents the
form of a cube, being very short and broad, articulated
firmly to the anteriorly projecting breast-bone, and more
loosely with the acromion and head of the humerus.
This bone, 53, would be classified amongst the "flat"
bones. It is almost as broad as it is long, especially at
its proximal end, which presents two articular surfaces
-one for the scapula, the other for the clavicle: the
expanse of the bone beyond these surfaces relates to the
formation of an adequate extent of attachmrnent for the




SKELETON OF THE MOLE.              197
deltoid, pectoral, and other great burrowing muscles.
All the other bones of the fore-limb are as extremely
modified for fossorial actions. The olecranon expands
transversely at its extremity, and the back part of the
ulna is produced into a strong ridge of bone.
The shaft of the radius is divided by a wide interosseous space from the ulna, and the head of the radius
is produced into a hook-shaped process like a second
"olecranon." The carpal series consists of five bones
in each row-the scaphoid being divided in the first, and
a sesamoid being added to the second row; moreover,
there is a large supplementary sickle shaped bone, extending from the radius to the metacarpal of the pollex,
giving increased breadth and a convex margin to the
radial side of the very powerful hand, and chiefly completing its adaptation to the act of rapidly displacing the
soil. The phalanges of the fingers are short and very
strong: the last are bifid at their ends for a firmer attachment of the strong claws. Little more of the hand than
these claws, and the digging or scraping edge, projects
beyond the sheath of skin enveloping the other joints,
and connecting the hand with the trunk.
The common position of the arm-bone is with its distal
end most raised. The fore-arm, with the elbow raised, is
in the state between pronation and supination, the radial
side of the hand being downwards, and the palm directed
outwards. The whole limb, in its position and structure,
is unequalled in the vertebrate series as a fossorial instrument, and only paralleled by the corresponding limb in
the mole-cricket (Gryllotalpa) amongst the insect-tribes.
No impediment is offered by the hinder parts of the
body or limbs when the thickest part of the animated
wedge has worked its way through the soil. The pelvis
17*




198          SKELETON OF THE BAT.
is remarkably narrow. The ossa innominata have coalesced with the sacrum, but not with each other, the
pubic arch remaining open.  The bodies of the sacral
vertebrae are blended together, and are carinate below;
their neural spines have coalesced to form a high ridge.
The acetabula look almost directly outwards. The head
of the femur has no pit for a round ligament. A fabella
is preserved behind the outer condyle. A hamular process is sent off from the head of the tibia and fibula; the
lower moieties of the shafts of these bones are blended
together. The toes are five in number on the'hind-feet as
in the fore, but are much more feebly developed. They
serve to throw back the loose earth detached by the
spade-shaped hands.
SKELETON OF THIE BAT.
The form of limb presented by the arm and hand of
the bat, offers the most striking contrast to the burrowing
trowel of the mole. Viewed in the living animal, it is a
thin, widely expanded sheet of membrane, sustained like
an umbrella by slender rays, and flapped by means of
these up and down in the air, and with such force and
rapidity, as, combined with its extensive surface, to react
upon the rare element more powerfully than gravitation
can attract the weight to which the fore-limbs are attached;
consequently, the body is raised aloft, and borne swiftly
through the air. The mammal now rivals the bird in its
faculty of progressive motion; it flies, and the instruments of its aerial course are called "wings." The whole
frame of the bat is in harmony with this faculty, but the
mammalian type of skeleton is in nowise departed from.
The vertebral formula of the common bat (Vespertilio




SKELETON OF THE BAT.                  199
murinus) (Fig. 42), is: 7 cervical, 12 dorsal, 7 lumbar, 3
sacral, and 8 caudal vertebra.  The chief characteristics
of the skeleton are: the gradual diminution of size of the
spinal column from the cervical to the sacral regions; the
absence of neural spines in the vertebrae beyond the dentata; a keeled sternum; long and strong, bent clavicles,
Fig. 42.
6 I,
SKELETON OF THFE BAT (Vlespertilio mnurin8ls).
58; broad scapulae, 51; elongated humeri, 53; more
elongated and slender radius, 55; and still longer and
more slender metacarpals and phalanges of the four fingers, ii, iii, iv, v, which are without claws, the thumb, i,
being short, and provided with a claw; the pelvis, 62, is
small, slender, and open at the pubis, 63; the fibula, 67,
is rudimental, like the ulna, 54, in the fore-arm.  The
common bat has a long and slender stilliform appendage




200          SKELETON OF THE LION.
to the heel, 68, which helps to sustain the caudo-femoral
membrane. The hind digits are five in number, short,
subequal, each provided with a claw; they are the instruments by which the bat suspends itself, head downwards, during its daily summer sleep, and continued
winter torpor.
SKELETON OF TIIE CARNIVOROUS
MA M MALIA.
The lion may be regarded as the type of a quadruped.
The well-adjusted proportions of the head, the trunk, the
fore-limbs, and tail concur with their structure to form
an animal swift in course, agile in leaps and bounds, terrible in the overpowering force of the blows inflicted by
the fore-limbs. The strong, sharp, much-curved, retractile talons, terminating the broad powerful feet; enable
the carnivore to seize the prey it has overtaken, and to
rend the body it has struck down. The jaws have a proportional strength, and are armed with fangs fitted to
pierce, lacerate, and kill.
The carnivorous character of the skull, as exemplified
by the sagittal and occipital crests, by the strength and
expanse of the zygomatic arches, by the breadth, depth,
and shortness of the jaws, by the height of the coronoid
processes, and by the depth and extent of the fossia of the
lower jaw for the attachment of the biting muscles, reaches
its maximum in the lion. The triangular occipital region
is remarkable for the depth and boldness of the sculpturing of its outer surface, indicative of the powerful muscles
working the whole skull upon the neck and trunk. The
conjoined paroccipitals and mastoids form a broad and




SKELETON OF THE LION.               201
thick capsular support for the back part of the acoustic
bulle. The pterygoid processes are imperforate. A wellmarked groove extends on each side of the bony palate
from the posterior to the anterior palatine foramina.
The premaxillaries are comparatively short, and one-half
of the lateral border of the nasals directly articulates with
the maxillaries. The antorbital foramina are largely
indicative of the size of the sensitive nerve supplying
the well-developed whiskers. Within the cranium  we
find that ossification has extended into the membrane
dividing the cerebrum from the cerebellum. This bony
tentorium extends above the petrosal to the ridge overhanging the Gasserian fossa; the petrosal is short, its
apex is neither notched nor perforated; the cerebellar
pit is very shallow. The sella-turcica is deep, and well
defined by both the anterior and posterior clinoids. The
rhinencephalic fossa is relatively larger in the lion than
in most carnivora, and is defined by a well-marked angle
of the inner table of the skull from the prosencephalic
compartment.  The olfactory chamber extends backwards both above and below the rhinencephalic fossa;
the upper part of the chamber is divided into two sinuses
on each side. The superior turbinals extend into the
anterior sinus, and below into the presphenoidal sinus.
All the bones of the skeleton are remarkable for their
whiteness and compact structure.
The vertebral formula of the lion (Fig. 43) is-7 cervical, 13 dorsal, 7 lumbar, 3 sacral, and 23 caudal. The
last cervical vertebra has the transverse processes imperforate, being formed only by diapophyses. The eleventh
dorsal is that toward which the spines of the other trunkvertebra, converge, and indicates the centre of motion of
the trunk in this bounding quadruped.  Eight pairs of




202           SKELETON OF THE LION.
ribs directly. join the sternum, which consists of eight
bones. The clavicles are reduced to clavicular bones,
58, suspended in the flesh. The supraspinal fossa of
the scapula is less deep than the infraspinal one, and
its border is almost uniformly convex; the acromion is
bifid, the recurved point being little larger than the extreinity or anterior point. The humerus, 53, is perforated
Fig. 43.
53
SKELETON OF THE LION (Felis leo).
above the inner condyle, but not between the condyles.
The radius, 55, and ulna, 54, are so articulated as to
permit a free rotation of the fore-paw. The scaphoid and
lunar bones are connate. Besides these, the bones of the
carpus are the cuneiforme; the pisiforme; the trapezium,
which gives an articulation to the ulnar side of the base
of the short metacarpus of the pollex; the trapezoides;
the magnum, which is the least of the carpal bones; the
ullciforme, which supports, as lusal.], the mietacarpals of




SKELETON OF' T'E LION.             203
the fourth and fifth digits; and the pisiforme, which projects far backwards, like a small calcaneum: there is also
a supplementary oscicle wedged in the interspace between
the prominent end of the scapllo-lunar bone and the
proximal end of the metacarpal of the pollex. The pollex
is retained on the fore-foot, and, like the other toes, is
terminated by a large, compressed, retractile, ungual
phalanx, forming a deep sheath, for the firm attachment
of the large curved and sharp-pointed claws.
The pelvis, 62, 63, 64, the femur, 65, the tibia, 66, and
fibula, 67, offer no remarkable modifications of structure;
the patella, 66, is well ossified, and there is a fabella, 67,
behind each condyle of the femur. The tarsal bones are
the astragalus; the scaphoides; the calcaneum; the cuboides, which, like the unciforme in the carpus,-supports
the two outer digits; the cuneiforme externum, which,
like the magnum, supports the middle digit; the cuneiforme medium, which, like the trapezoides, supports the
second digit; and the cuneiforme internum, which supports the rudiment of the metatarsal of the first or innermost digit.
The last or ungual phalanx, in both fore and hind feet,
has a bony sheath at its base for the firmer implantation
of the claw; and its joint is at the back part of the proximal end of the phalanx, whereby it can be drawn upwards
upon the second phalanx, when the claw becomes concealed in the fold of integument forming the interspace
of the digits.
This state of retraction is constantly maintained, except
when overcome by an extending force, by means of elastic
ligaments. The principal one arises from the outer side
and distal extremity of the second phalanx, and is inserted
into the superior angle of the last phalanx; a second arises




204          SKELETON OF THE LION.
from the outer side and proximal end of the second phalanx, and passes obliquely to be inserted at the inner side
of the base of the last phalanx. A third, which arises
from the inner side and proximal extremity of the second
phalanx, is inserted at the same point as the preceding.
The tendon of the flexor profundus perforans is the antagronist of the elastic ligaments. By the action of that
muscle, the last phalanx is drawn forwards and downwards, and the claw exposed. In order to produce the
full effect of drawing out the claw, a corresponding action
of the extensor muscle is necessary, to support and fix
the second phalanx; by its ultimate insertion in the terminal p)halanx, it serves also to restrain and regulate the
actions of the flexor muscle. As the phalanges of the
hind-foot are retracted in a different direction to those of
the fore-foot, i. e. directly upon, and not by the side of the
second phalanx, the elastic ligaments are differently disposed, but perform the same main office.
It seems scarcely necessary to allude to the final intention of these beautiful structures, which are, with some
slight modifications, common to the genus Felis. The
claws being thus retracted within folds of the integument,
are preserved constantly sharp, and ready for their destined functions, not being blunted and worn away in the
ordinary progressive motions of the animal; while at the
same time the sole of the foot, being padded, such soft
parts only are brought in contact with the ground as
conduce to the noiseless tread of the stealthy feline tribe.
This highly-developed unguiculate structure, with the
dental system and concomitant modifications of the skull,
complete the predatory character of the typical Carnivora.




SKELETON OF THE KANGAROO.               205
SKELETON OF THE KANGAROO.
Australia possesses an indigenous race of herbivorous
mammals, created to enjoy existence on its grassy plains.
But the climate of this fifth continent, as, from its extent,
it has been termed, is subject to droughts of unusual duration; and the parched up grass, ignited by the electric
bolt or other cause, often raises a conflagration of fearful
extent, and leaves a correspondingly wide-spread blackened desert. To the antelope, and other ruminants of
Fig. 44.
15
SKELETON OF THE KANGAROO (ilfacropts elegans).
tropical or warmer latitudes, swiftness of limb has been
given, which enables them to migrate to river valleys,
where the vegetation is preserved from the influence of
the dry season. Australia, however, is peculiar for its
18




206      SKELETON OF THE KANGAROO.
scanty supply of perennial streams; the torrents of the
brief periods of rain are reduced to detached pools in the
dry season, and these are parched up in the long droughts,
leaving hundreds of miles of the country devoid of surface water. If, then, the parent herbivore could traverse
the required distance to quench its thirst, or satisfy its
hunger, the tender young would be unable to follow the
dam. A modification of the procreative process has accordingly been superinduced, which characterizes the
Australian mammals; the young are prematurely brought
forth of embryonic size and helplessness, and are transferred to a pouch of inverted skin, concealing the udder;
and in this marsupium, as in a well-stored vehicle, they
are easily transferred by the parent to any distance to
which the climatal conditions may compel her to migrate.
The economy of this portable nursery, the requisite manipulation of the suckling young therein suspended from
the teat, demand a certain prehensile power of the forelimbs, a freedom of the digits, with some opposable faculty
in them, and the possession of so much sense of touch as
would be impossible were the digit to be incased in a
hoof; the horny matter is accordingly developed only on
the upper surface of the finger-end, and is in the form of
a claw. But the unguiculate pentadactyle extremitythough a higher grade of structure in the progress of
limbs-is not suited for the exigences of the herbivore,
and would have appeared utterly incompatible with an
existence dependent on grazing in wild pastures, had we
argued from knowledge restricted to the forms and structures of the hoofed herbivores of the Europaeo-Asiatic,
African, and American continents. Htow, then, it may
be asked, is this difficulty overcome in the case of a grazing animal, necessarily a marsupial, and consequently an




CONDITIONS OF MARSUPIAL STRUCTURE. 207
unguiculate. one.? The answer need only be a reference
to Fig. 44; the requisite faculty of migration of the parent
with the tender offspring is gained by transferring the
locomotive power to the hinder pair of limbs extraordinarily developed, and aided by a correspondingly powerful tail; the fore-limbs being restricted in their development to the size requisite for the marsupial offices and
other accessory uses.
This is the condition or explanation of the seemingly
anomalous form  and proportions of the kangaroo-so
strange, indeed, that the experienced naturalists, Banks
and Solander, may well be excused for surmising they
had seen a huge bird when they first caught a glimpse
of the kangaroo in the strange land which they, with
Cook, discovered.
The rapid course of the kangaroo is by a succession of
leaps, in which twenty to thirty yards are cleared at a
bound; the herbivore, instead of a swift courser on four
pretty equally developed hoofed extremities, is, in Australia, a leaping animal; and the saltatorial modification
of the mammalian skeleton is here shown in that of one
of the swiftest and most agile of the numerous species of
kangaroo, the 1facropus elegans.
In this kangaroo, 13 vertebrae are dorsal, 6 are lumbar,
2 are sacral, and 28 are caudal, the first fourteen of which
have hbemapophyses. These elements coalesce at their
distal ends, and form small hbemal arches; they overspan
and protect from pressure the great bloodvessels of the
tail, the powerful muscular fasciculi of which derive inc~reased surface of attachment from these h3emal arches.
The pelvis is long; the strong prismatic ilia, 52, and the
ischia, 63, carry out the great flexors and extensors of the
thigh to a distance from their point of insertion-the




208       SKELETON OF TIIE KANGAROO.
femur, which makes these muscles operate upon that lever
at a most advantageous angle; the trunk, borne along in
the violent leaps, needs to be unusually firmly bound to
the pelvic basis of the chief moving powers. Accordinogly, we find a pair of bones, 64', extending forwards
from the pubic symphysis, 64, along the ventral walls,
giving increased bony origin to the unusually developed
median abdominal muscles attaching the thorax to the
pelvis; and these " marsupial bones," as they are called,
have accessory functions relating to reproduction in both
sexes of the marsupial quadrupeds. The femur, 65, is
more than twice the length of the humerus; it is proportionally strong, with well-developed great and small
"trochanters," and a "fabella" behind one or both condyles. The patella is unossified. The fibula, 67, is immovably united to the lower half of the tibia.  This
bone, 66, is of unusual length and strength, and is firmly
interlocked below with the trochlear astragalus.  The
heel-bone sends backwards a long lever-like process for
the favorable insertion of the extensors of the foot. This
member is of very unusual length. The innermost toe,
or hallux, is absent; the second and third toes are extremely slender, inclosed as far as the ungual phalanx in a
common fold of integument, and reduced to the function
of cleansing the fur. The offices of support and progression are performed by the two outer toes, iv and v, and
principally by the fourth, which is enormously developed,
and terminated by a long, strong, three-sided, bayonetshaped claw; these two toes are supported, as usual, by
the os cuboides, which is correspondingly large, whirst
the naviculare and the cuneiform bones are proportionally reduced in size. The bones of the fore-limb, though
comparatively diminutive, present all the complexities of




SKELETON OF THE QUADRUMANA.   209
structure of the unguiculate limb. The clavicle, 58, connects the acromion with the sternum, and affords a fulcrum
to the shoulder-joint. The humerus, articulating below
with a radius and ulna which can rotate on each other,
develops ridges above both inner and outer condyles for
the extended origin of the muscles of pronation and
supination. The brachial artery pierces the entocondyloid
ridge. The carpal bones, answering to the scaphoid and
lunar in the human wrist, are here confluent. The digits
are five in number, enjoy free, independent movements,
ard are each terminated by a sharp-curved claw.
SKELETON OF THE QUADRUMANA.
The sloth is an exclusively arboreal animal; its diet is
foliage; it has but to bring its mouth to the leafy food,
and the lips and tongue serve to strip it from the branches.
The extremities, as we have seen, serve mainly to climb
and cling to branches, and occasionally to hook down a
tempting twig within reach of the mouth. There is, however, another much more extensive and diversified order
of arboreal mammals destined to subsist on the fruits and
other more highly developed products of the vegetable
kingdom than mere leaves. In the monkeys, baboons,
and apes the extremities are endowed with prehensile
faculties of a more perfect and varied character than in
the sloths; and this additional power is gained by a full
development of the digits in normal number, with free
and independent movements, which in one of them-the
first or innermost-are such as that it can be opposed to
the rest, so that objects of various size can be grasped.
This modification converts a foot into a hand; and, as the
18*




210         SKELETON  OF THE,APE TRIBE.
mammals in question have the opposable "thumb" on
both fore and hind limbs, they are called "quadrurnana,"
or four-handed. The rest of the limb manifests a correFig. 46.
Fig. 45. 
SKLTN62OIi'Pthcsstyu)ADMN.5`6
SKELETONS OF ORANG (Pithecet8 sat,1lts) AND -MAN.




STRUCTURE OF THE APE AND MAN.    211
sponding complexity or perfection of structure; the trunk
is adjusted to accord with the actions of such instruments,
and the brain is developed in proportion with the power
of executing so great a variety of actions and movements
as the four-handed structure gives capacity for.
In the skull of the quadrumana are seen indications of
a concomitant perfection of the outer senses; the orbits
are entire, and directed forwards, with their outlets almost
on the same plane; both eyes can thus be brought to bear
upon the same object. The rest of the face, formed by
the jaws, -now begins to bear a smaller proportion to the
progressively expanding cranium. The neck, of moderate length, has its seven vertebrae well developed, with
the costal processes large in the fifth and sixth: the dorsal
vertebras, twelve, in the species figured (Pithecus satyrus),
show, by the convergence of their spines towards the vertical one on the ninth, that this is the centre of movement
of the trunk. The lumbar vertebrae are four in number;
in the inferior monkeys they are seven, and the anterior
ones are firmly interlocked by well-developed anapophyses and metapophyses. The sacrum is still long and
narrow. The tail, in some of the lower quadrumana, is
of great length, including 30 vertebrae in the red monkey
(Cereopithecus ruber), in which the anterior ones are complicated by having haemal arches. The clavicles are entire in all quadrumana. The humerus has its tuberosities
and condyloid crests well developed. The radius rotates
freely on the ulna. The wrist has nine bones, owing to
a division of the scaphoid, besides supplementary sesamoids adding to the force of some of the muscles of the
hand; the thumb is proportionally shorter in the fore than
in the hind foot. The patella is ossified, and in most
baboons and monkeys there is a fabella behind each con



212    STRUCTURE OF THE APE AND MAN.
dyle of the femur. The fibula is entire, and articulated
with the tibia at both ends. The tarsus has the same
number and relative position of the bones as in man; but
the heel-bone is shorter, and the whole foot rather more
obliquely articulated upon the leg, the power of grasping
being more cared for than that of supporting the body;
the innermost toe forms a large and powerful opposable
thumb.
- There is a well-marked gradation in the quadrumanous
series from the ordinary quadrupedal to the more bipedal
type. In the lemurs and South American monkeys, the
anterior thumb is shorter and much less opposable than
the hinder one; in the spider-monkeys it is wanting, and
a compensation seems to be given by the remarkable prehensile faculty of the: curved and callous extremity of the
long tail. This member, in the African and Asiatic monkeys, is not prehensile, but the thumb of the fore-hand is
opposable. In the true apes, the tail is wanting, i. e. it is
reduced to the rudiment called "os coccygis;" but the
fore-arms are unusually developed in certain species, hence
called "long-armed apes;"  These can swing themselves
rapidly from bough to bough, traversing wide spaces in
the aerial leap. The orang (Fig. 45) is also remarkable
for the disproportionate length of the arms, but this difference from man becomes less in the chimpanzees. The
large species called Gorilla, which of all brutes makes the
nearest approach to man, is still strictly " quadrumanous;"
the great toe, or "hallux," being a grasping and opposable digit. But the hiatus that divides this highest of the
ape tribe from the lowest of the human species, is more
strikingly and decisively manifested in the skull (Fig. 50).
The common teeth in the male gorilla are developed, as
in the male orang, to proportions emulating the tusks of




STRUCTURE OF THE APE AND MAN.    213
the tiger; they are, however, weapons of combat and defence in these great apes, which are strictly frugivorous.
Nevertheless, the muscles that have to work jaws so armed
require modifications of the cranium akin to those that
characterize the lion, viz: great interparietal, 7, and occipital, 3, cristhe and massive zygomatic arches. The spines
of the cervical vertebrae are greatly elongated in relation
to the support of such a skull, the facial part of which
extends so far in advance of the joint between the head
and neck. The chimpanzees, moreover, differ from man
in having thirteen pairs of thoracic movable ribs. The
long and flat iliac bones, 62, the short femora, 65, so articulated with the leg-bones, 66, as to retain habitually a
bent position of the knee, the short calcanea, c, and the
inward inclination of the sole of the foot, all indicate, in
the highest as in the lowest quadrumana, an inaptitude
for the erect position, and a compensating gain of climbing power favorable for a life to be spent in trees.
In the osteological structure of man (Fig. 46), the vertebrate archetype is furthest departed from by reason of
the extreme modifications required to adjust it to the peculiar posture, locomotion, and endless variety of actions
characteristic of the human race.
As there is nothing, short of flight, done by the moving
powers of other animals that serpents cannot do by the
vertebral column alone, so there is no analogous action
or mode of motion that man cannot perform, and mostly
better, by his wonderfully developed limbs. The reports
of the achievements of our athletes, prize wrestlers, prize
pedestrians, funambulists, and the records of the sharkpursuing and shark-slaying amphibious Polynesians, of
the equestrian people of the Pampas, of the Alpine
chasers of the chamois, and of the scansorial bark-strip



214  ADAPTATION OF THE HUMAN SKELETON
pers of Aquitaine, concur in testifying to the intensity of
those varied powers, when educed by habit and by skilled
practice. The perfection of almost all modifications of
active and motive structures seems to be attained in the
human frame, but it is a perfection due to especial adaptation of the vertebrate type, with a proportional departure from its fundamental pattern. Let us see how this
is exemplified in the skeleton of man (Fig. 46), viewing
it from the foundation upwards.
In the typical mammalian foot, the digits decrease from
the middle to the two extremes of the series of five toes;
and in the modifications of this type, as we have traced
them through the several gradations (pp. 185, 187, Figs.
35-39), the innermost,;, is the first to disappear. In man,
it is the seat of excessive development, and receives the
name of "hallux," or "great toe;" it retains, however, its
characteristic inferior number of phalanges. The tendons
of a powerful muscle, which in the orang aad chimpanzee
are inserted into the three middle toes, are blended in
man into one, and this is inserted into the hallux, upon
which the'force of the muscle now called "flexor longus
pollicis" is exclusively concentrated.
The arrangement of other muscles, in. subordination to
the peculiar development of this toe, makes it the chief
fulcrum when the weight of the body is raised by the
power acting upon the heel, the whole foot of man exemplifying the lever of the second kind. The strength and
backward production of the heel-bone, c, relate to the
augmentation of the power. The tarsal and metatarsal
bones are coadjusted so as to form arches, both lengthwise and across, and receive the superincumbent weight
from the tibia on the summit of a bony vault, which has
the advantage of a certain elasticity combined with ade



TO THE ERECT POSTURE.              215
quate strength. In proportion to the trunk, the pelvic
limbs are longer than in any other animal; they even
exceed those of the kangaroo, and are peculiar for the
superior length of the femur, 65, and for the capacity of
this bone to be brought, when the leg is extended, into
the same line with the tibia, 66; the fibula, 67, is a distinct bone. The inner condyle of the femur is longer
than the outer one, so that the shaft inclines a little outwards to its upper end, and joins a neck longer than in
other animals, and set on at a very open angle. The
weight of the body, received by the round heads of the
thigh-bones, is thus transferred to a broader base, and its
support in the upright posture facilitated. The pelvis is
modified so as to receive and sustain better the abdominal
viscera, and to give increased attachment to the muscles,
especially the "glutei," which, comparatively small in
other mammals, are in man vastly developed to balance
the trunk upon the legs, and reciprocally to move. these
upon the trunk. The great breadth and anterior concavity of the ilium, 62, are characteristic modifications of
this bone in man. The pelvis is more capacious, the
tuberosity of the ischium is less prominent, and the symphysis pubis shorter, than in apes. The tail is reduced
to three or four stunted vertebrae, anchylosed to form the
bone called "os coccygis." The five vertebrae which coalesce to form the sacrum, are of unusual breadth, and the
free or "true" vertebrae, that rest on the base of the sacral
wedge, gradually decrease in size to the upper part of the
chest; all the free vertebrae, divided into five lumbar,
twelve dorsal, and seven cervical, are so articulated as to
describe three slight and graceful curves, the bend being
forward in the loins, backward in the chest, and forward
again in the neck. A soft elastic cushion, of "interver



216  MODIFICATIONS OF THE HUMAN SKELETON
tebral" substance, rests between the bodies of the vertebrse. The distribution and libration of the trunk, with
the superadded weight of the head and arms, are favored
by these gentle curves, and the shock in leaping is broken
and diffused by the numerous elastic intervertebral joints.
The expansion of the cranium behind, and the shortening
of the face in front, give a globe-like form to the skull,
which is poised by a pair of coudyles, advanced to near
the middle of its base upon the cups of the atlas; so that
there is but a slight tendency to incline forwards when
the balancing action of the muscles ceases, as when the
head nods during sleep in an upright posture.
The framework of the upper extremity shows all the
perfections that have been superinduced upon it in the
mammalian series, viz: a complete clavicle, 58, antibrachial bones, 54, 55, with rotatory movements as well as
those of flexion and extension, and the five digits, 57,
free and endowed with great extent and variety of movements: of these, the innermost, which is the first to
shrink and disappear in the lower mammalia, is in man
the strongest, and is modified to form an opposable thumb
more powerful and effective than in any of the quadrumana. The scapula, 51, presents an expanded surface of
attachment for the muscles which work the arm in its
free socket; the humerus, 53, exceeds in length the bones
of the fore-arm. The carpal bones, 56, are eight in number, called scaphoides, lunare, cuneiforme, pisiforme, trapezium, trapezoides, magnum, and unciforme: of these
the scaphoid and unciforme are compound bones; i. e.
they consist each of two of the bones of the type-carpus,
connate.
In the human skull, viewed in relation to the archetype, as exemplified in the fish and the crocodile, the fol



IN RELATION TO THE ARCHETYPE.    217
lowing extreme modifications have been established. In
the occipital segment, the heemal arch is detached and
displaced, as in all vertebrates above fish; its pleurapophysis (scapula, 51) has exchanged the long and slender
for the broad and flat form; the haemapophysis (coracoid,
52) is rudimental, and coalesces with 51. The neurapophyses (exoccipitals, 2) coalesce with the neural spine
(superoccipital), and next with the centrum (basioccipital).
This afterwards coalesces with the centrum (basisphenoid)
of the parietal segment. With this centrum also the
neurapophyses, called "alisphenoids," and the centrum of
the frontal vertebra, called " presphenoid," become anchylosed. The neural spine (parietal) retains its primitive
distinctness, but is enormously expanded, and is bifid, in
relation to the vast expansion of the brain in man. The
parapophysis (mastoid) becomes confluent with the tympanic, petrosal, and squamosal, and with the pleurapophysis, called "stylohyal," of the hbemal (hyoidian) arch.
The hemapophysis is ligamentous, save at its junction
with the haemal spine, when it forms the ossicle called
"lesser cornu of the hyoid bone," the spine itself being
the basihyal or body of the hyoid bone. The whole of
this inverted arch is much reduced in size, its functions
being limited to those of the tongue and larynx, in regard
to taste, speech, and deglutition. The neurapophyses
(orbitosphenoids) becoming confluent with the centrum
(presphenoid) of the frontal vertebra, and the latter coalescing with that of the parietal vertebra, the compound
bone called "sphenoid" in anthropotomy results, which
combines the centrums and neurapophyses of two cranial
vertebrae, together with a diverging appendage (pterygoid) of the maxillary arch.
The knowledge of the essential nature of such a com19




218  MODIFICATIONS OF THE HUMAN SKELETON
pound bone gives a clue to the phenomena of its development from so many separate points, which final causes
could never have satisfactorily afforded. As the centrum,
5, becomes confluent with No. 1, a still more complex
whole results, which has accordingly been described as a
single bone, under the name of " os spheno-occipital" in
some anthropotomies. Such a bone has not fewer than
twelve distinct centres of ossification, corresponding with
as many distinct bones in the cold-blooded animals that
depart less from the vertebrate archetype. The spine of
the frontal vertebra (frontal bone) is much expanded and
bifid, like the parietal bone; but the two halves more frequently coalesce into a single bone, with which the parapophysis (postfrontal) is connate. The pleurapophysis of
the hemal arch (tympanic bone) is reduced to its function
in relation to the organ of hearing, and becomes anchylosed to the petrosal, the squamnosal, and the mastoid.
The hmmapophysis is modified to form the dentigerous
lower jaw, but articulates, as in other mammals, with a
diverging appendage (squamosal) of the antecedent haemal
arch, now interposed between it and its proper pleurapophysis; the two hemapophyses, moreover, become confluent at their distal ends, forming the symphysis mandibulhe.
The centrum of the first or nasal vertebra, like that of
the last vertebra in birds, is shaped like a ploughshare,
and is called "vomer;" the neurapophyses have been subject to similar compression, and are reduced to a pair of
vertical plates, which coalesce together, and with parts of
the olfactory capsules (upper and middle turbinals) forming the compound bone called " sethmoid;" of which the
neurapophyses (prefrontals) form the "lamina perpendicularis" in human anatomy. The prefrontals assume this




IN RELATION TO THE ARCHETYPE.    219
confluence and concealed position even in some fishes —
xi4hias, e. g. —and repeat the character in all mammalia
and in most birds; but they become partially exposed in
the ostrich and the batrachia. The spine of the nasal
vertebra (nasal bones) is usually bifid, like those of the
two succeeding segments; but it is much less expanded.
The haemal, called "maxillary" arch, is formed by the
pleurapophyses (palatines) and by the hoamapophyses
(maxillaries), with which the halves of the bifid hbemal
spine (premaxillaries) are partly connate, and become
completely confluent. Each moiety, or premaxillary, is
reduced to the size required for the lodgement of two vertical incisors: as the canines in man do not exceed the
adjoining teeth in length, and the premolars are reduced
to two in number, the alveolar extent of the maxillary is
short, and the whole upper jaw is very slightly prominent.
Of the diverging appendages of the maxillary arch, the
more constant one, called "pterygoid," articulates with
the palatine, but coalesces with the sphenoid; the second
pair, formed by the malar, 26, and squamosal, 27, has been
subject to a greater degree of modification; it still performs the function assigned to it in lizards and birds,
where it has its typical ray-like figure, of connecting the
maxillary with the tympanic; but the second division of
the appendage (squamosal) which began to expand in the
lower mammalia, and to strengthen, without actually
forming part, of the walls of the brain-case, now attains
its maximum of development, and forms an integral constituent of the cranial parietes, filling up a large cavity
between the neural arches of the occipital and parietal
segments. It coalesces, moreover, with the tympanic,
mastoid, and petrosal, and forms, with the subsequently




220 GENERAL AND SPECIAL TERMS IN OSTEOLOGY.
anchylosed stylohyal, a compound bone called " temporal"
in human anatomy. The key to the complex beginning
of this "cranial" bone is again given by the discovery of
the general pattern on which the skulls of the vertebrate
animals have been constructed. In relation to that pattern, or to the archetype vertebrate skeleton, the human
temporal bone includes two pleurapophyses, 38 and 28, a
parapophysis, 8, part of a diverging appendage, 27, and a
sense-capsule, 16.
The departure from the archetype, which we observe
in the human skull, is most conspicuous in the neural
spines of the three chief segments, which, archetypally,
may be regarded as deformities by excess of growth to
fulfil a particular use, dependent on the maximization of
the brain; the deviation is again marked by arrest of
growth or suppression of parts, as e. g. in certain parapophyses, and in the haemal arch of the parietal segment; it
is most frequently exemplified in the coalescence of parts
primarily and archetypally distinct; and it is finally manifested by the dislocation of a part, viz: the haemal arch
of the occipital segment —the diverging rays of which
have become the seat of that marvellous development
which has resulted in the formation of the osseous basis
of the human hand and arm. With the above explanation the structure of the human skull can be intelligibly
comprehended, and not merely empirically understood,
as through the absolute descriptions penned in reference
to material and utilitarian requirements, and without reference to the great scale of vertebrate structures, of which
man is the summit.
The fruit of a series of comparisons, extended over all
the vertebrate-kingdom, being the recognition of the
archetype governing the structure of the vertebrate skele



GENERAL AND) SPECIAL TERMS IN OSTEOLOGY. 221
ton, the expression of such knowledge has necessitated
the use of general terms, such as "vertebra," for the segments of the skeleton, "neurapophyses," for a constant
element of such segment, and the like "general names"
for other elements. When any of these elements are
modified for special functions, then also a special name
for it becomes a convenience, as when a "pleurapophysis" becomes a jaw or blade-bone, &c., a " diverging appendage" an arm or a leg. Deep thinking anatomists
have heretofore caught glimpses of these higher, or more
general, relations of the vertebral elements, when much
modified or specialized, as e. g. in the head, and have tried
to give expression to the inchoate notion, as when Spix
called the " maxillary arch" the " arm of the head." These
glimpses of a great truth were, however, ill received; and
Cuvier alluded to them, with ill-disguised contempt, as
being unintelligible and mystical jargon, in his great work
on Fossil Animals (1825). But the error or obscurity
lay rather in the mode of stating the relationship of certain bones of the head to those of the trunk, than in the
relationship itself: in the endeavor, e. g. to express the
relation by special instead of general terms. Even in
1845, the learned and liberal-minded editor of Baron Cu.
vier's last course of lectures, M. de Saint Agy, commenting upon the osteological essays of Spix and Oken,
remarks: "For my part, an'upper-jaw' is an'upper-jaw,'
and an'arm' is an'arm.' One must not seek to originate
an osteology out of a system of metaphysics."' But a
jaw is not the less a jaw because it is a " haemapophysis,"
1 "Pour moi, une machoire supericure est une machoire superieure,
et un bras est un bras, 11 ne faut pas chercher A faire sortir l'osteologie
d'un systEme de metaphysique."
10



222              FACIAL ANGLE.
nor is an arm the less an arm because it is a "diverging
appendage." In the same spirit a critic might write:
"Newton calls this earth a'planet,' and the moon a'satellite;' for me the earth is an earth, and the moon is a
moon. One must not strive to make an ouranology out
of a system of metaphysics." After the first recognition
of a thing, one may seek to penetrate, and succeed in
knowing, its essential nature, and yet keep within the
bounds of nature.
In no class of vertebrate animals is the progressive
superiority of the cranium over the face marked by such
distinct stages as in the mammalia. Various methods
of determining these proportions have been proposed;
but the only satisfactory one is by comparing vertical
sections of the skull, as in the series figured in the cuts
47-52.
In the cold-blooded ferocious crocodile (Fig. 47), the
Fig. 47.
CROCODILE.
cavity for the brain, in a skull three feet long, will
scarcely contain a man's thumb. Almost all the skull is
made up of the instruments for gratifying an insatiable
Fig. 48.
ALBATROSS.




PROGRESSIVE EXPANSION OF CRANIUM. 223
propensity to slay and devour: it is the material symbol
of the lowest animal passion.
In the bird (Fig. 48), the brain-case has expanded vertically and laterally, but is confined to the back part of
the skull. In the small singing birds, with shorter beaks,
the proportion of the cranial cavity becomes much greater.
Fig. 49.
DOG.
In the dog (Fig. 49), the brain-case, with more capacity,
begins to advance further forward. In the chimpanzee
Fig. 50.
CHIMPANZEE.
(Fig. 50), the capacities or area of the cranium and face
are about equal. In man, the cranial area vastly surpasses
that of the face.




224-  PROGRESSIVE EXPANSION OF CRANIUM.
A difference in this respect is noticeable between the
savage (Fig. 51) and civilized (Fig. 52) races of mankind;
but it is immaterial as compared with the contrast in this
respect presented by the lowest form of the human head
(Fig. 51) and the highest of the brute species (Fig. 50).
Fig. 51;                      Fig 52.
AUSTRALIAN.                  EUROPEAN'.
Such as it is, however, the more contracted cranium is
commonly accompanied by more produced premaxillaries
and thicker walls of the cranial cavity, as is exemplified
in the negro or Papuan skull.
If a line be drawn from the occipital condyle along the
floor of the nostrils, and be intersected by a second touching the most prominent parts of the forehead and upper
jaw, the intercepted angle gives, in a general way, the
proportions of the cranial cavity and the grade of intelligence; it is called the facial angle. In the dog, this angle
is 20~; in the great chimpanzee, or gorilla, it is 40~, but
the prominent superorbital ridge occasions some exaggeration; in the Australian it is 850; in the European it is
95~. The ancient Greek artists adopted, in their beau
ideal of the beautiful and intellectual, an angle of 100.




CONCLUDING REMARKS.               225
CONCLUDING REMARKS.
A retrospect of the varied forms and proportions of the
skeletons of animals, whether modified for aquatic, aerial,
or terrestrial life, will show that whilst they were perfectly and beautifully adapted to the sphere of life and
exigences of the species, they adhered with remarkable
constancy to that general pattern or archetype which was
first manifested on this planet, as Geology teaches, in the
class of fishes, and which has not been departed from even
in the most extremely modified skeleton of the last and
highest form which Creative Wisdom has been pleased to
place upon this earth.
It is no mere transcendental dream, but true knowledge
and legitimate fruit of inductive research, that clear insight into the essential nature of each element of the bony
framework, which is acquired by tracing them step by
step, as e. g. from the unbranched pectoral ray of the
lepidosiren to the equally small and slender but bifid
pectoral ray of the amphiume, thence to the similar but
trifid ray of the proteus, and through the progressively
superadded structures and perfections of the limbs in
higher reptiles and in mammals. If the special homology of each part of the diverging appendage and its
supporting arch are recognizable from man to the fish,
we cannot close the mind's eye to the evidences of that
higher law of archetypal conformity on which the very
power of tracing the lower and more special correspondences depend.
Buffon has well remarked, in the Introduction to his
great work on Natural History: " It is only by compar



226           CONCLUDING RlMARKS.
ing that we can judge, and our knowledge turns entirely
on the relations that things bear to those which resemble
them and to those which differ from them; so, if there
were no animals, the nature of man would be far more
incomprehensible than it is."
And if this be true, as to man's general nature and
powers, it is equally so with regard to his anatomical
structure.
In the same spirit our philosophic poet felt that"'Tis the sublime of man,
Our noontide majesty, to know ourselves
Part and proportions of a wondrous whole."-CoLERIDGE.
Vertebrated animals of progressively higher grades of
structure have existed at successive periods of time on
this planet, and they were constructed on a common plan
with those that still exist.
Some have concluded, therefore, that the characters of
a species became modified in successive generations, and
that it was transmuted into a higher species; a reptile,
e. g. into a mammal; an ape, into a negro. Let us consider, therefore, the import and value of the osteological
differences between the gorilla-the highest of all apesand man, in reference to this "transmutation hypothesis."
The skeleton of an animal may be modified to a certain
extent by the action of the muscles. By the development of the processes, ridges, and crests, the anatomist
judges of the muscular power of the individual to whom
a skeleton under comparison has appertained. A very
striking difference from the form of the human cranium
results from the development of certain crests and ridges
for the attachment of muscles, in the great apes; but
none of the more important differences, on which the




CONCLUDING REMARKS.                227
naturalist relies for the determination of the genus and
species of the orangs and chimpanzees, have such an
origin or dependent relation. The great superorbital
ridge, e. g. against which the facial line rests in Fig. 50,
is not the consequence of muscflar action or development: it is characteristic of the genus Troglodytes from
the time of birth; and we have no grounds for believing
it to be a character to be gained or lost through the operations of external causes, inducing particular habits
through successive generations of a species.
No known cause of change productive of varieties of
mammalian species could operate in altering the size,
shape, or connections of the prominent premaxillary
bones, which so remarkably distinguish the great Troglodytes gorilla from the lowest races of mankind. There is
not, in fact, any other character than that founded upon
the development of bone for the attachment of muscles,
which is known to be subject to change through the
operation and influence of external causes. Nine-tenths
of the differences which have been cited (see the Transactions of the Zoological Society, Vol. iii. p. 413), as distinguishing the great chimpanzee from the human species,
must stand in contravention of the hypothesis of transmutation and progressive development, until the acceptors
of that hypothesis are enabled to adduce the facts demonstrative of the conditions of the modifiability of such
characters. Moreover, as the generic forms of the ape
tribe approach the human type, they are represented by
fewer species. The unity of the human species is demonstrated by the constancy of those osteological and dental
peculiarities which are seen to be most characteristic of
the bimana in contradistinction from the quadrumana.
Man is the sole species of his genus (homo)-the sole




228          CONCLUDING REMARKS.
representative of his order (bimana); he has no nearer
physical relations with the brute kind than those that
belong to the characters which link together the unguiculate division of the mammalian class.
Of the nature of the creative acts by which the successive races of animals were called into being, we are ignorant. But this we know, that as the evidence of unity
of plan testifies to the oneness of the Creator, so the
modifications of the plan for different modes of existence
illustrate the beneficence of the Designer. Those structures, moreover, which are at present incomprehensible
as adaptations to a special end, are made comprehensible.
on a higher principle, and a final purpose is gained in
relation to human intelligence; for in the instances where
the analogy of humanly invented machines fails to explain the structure of a divinely created organ, such
organ does not exist in vain if its truer comprehension,
in relation to the Divine idea, or prime Exemplar, lead
rational beings to a better conception of their own origin
and Creator.




ON THE PRINCIPAL
FORMS AND STRUCTURES OF THE TEETH.
AT the commencement of the Treatise on the Principal Forms of the Skeleton, it was stated that " tooth,"
like "bone," was the result of the combination of certain
earthy salts with a pre-existing cellular basis of animal
matter. The salts, as shown in a subjoined table, are
nearly the same as those in bone, but enter in a larger
proportion into the composition of tooth, and render it a
harder body. So composed, teeth are peculiar to the
back-boned (vertebrate) animals, and are attached to
parts of the mouth, commonly to the jaws. They present many varieties as to number, size, form, structure,
position, and mode of attachment, but are principally
adapted for seizing, tearing, dividing, pounding, or grinding the food. In some species they are modified to serve
as formidable weapons of offence and defence; in others,
as aids in locomotion, means of anchorage, instruments
for uprooting or cutting down trees, or for transport and
working of building materials. They are characteristic
of age and sex; and in man they have secondary relations subservient to beauty and to speech.
Teeth are always intimately related to the food and
20




230            SUBSTANCE OF TEETH.
habits of the animal, and are, therefore, highly interesting to the physiologist. They form, for the same reason,
important guides to the naturalist in the classification of
animals; and their value, as zooloFig. 53.      gical characters, ij enhanced by the
facility with which, from their position, they can be examined in living or recent animals; whilst the
A.ddi  /durability of their tissues renders
<l- A —.'them not less available to the pala3onthologist in the determination of'  "'.the nature and affinities of extinct
species, of whose organization they
are often the sole remains discoverable in the  deposits of former
periods of the earth's history.
The substance of teeth is not so
uniform  as in bone, but consists
commonly of two or more tissues,
*!.W  characterized by the proportions
of their earthy and animal constituents, and by the size, form, and
direction of the cavities in the ani-mal basis which contain the earth,
SECTION OF HUMAN INCISOR  the fluid, or the vascular pulp.
TOOTH (magnified).
The tissue which forms the body
of the tooth is called "dentine" (dentinum, Lat.), Fig.
53, 1.
The tissue which forms the outer crust of the tooth is
called the "cement" (ccementum, and crusta petrosa, Lat.),
ib. 3.
The third tissue, when present, is situated between the
dentine and cement, and is called L enamel" (enzcustum,
or adamnas, Lat.), ib. 4.




DEFINITION OF DENTAL TISSUES.          231
"Dentine" consists of an organized animal basis disposed in the form of extremely minute tubes and cells,
and of earthy particles; these particles have a twofold
arrangement, being either blended with the animal matter of the interspaces and parietes of the tubes and cells,
or contained in a minutely granular state in their cavities.
The density of the dentine arises principally from the
proportion of earth in the first of these states of combination. The tubes and cells contain, besides the granular
earth, a colorless fluid, probably transuded " plasma," or
"' liquor sanguinis," and thus relate not only to the mechanical conditions of the tooth, but to the vitality and
nutrition of the dentine.
In hard or true dentine, the tubes called "dentinal
tubes" diverge from the hollow of the tooth, called "pulpcavity," and proceed with a slightly wavy course at right
angles, or nearly so,-to the outer surface. The hard substance of the tooth is thus arranged in hollow columns,
perpendicular to the plane of pressure, and a certain
elasticity results from their curves: they are upright
where the grinding surface of the crown receives the
appulse of the opposing tooth, and are horizontal where
they have to resist the pressure of contiguous teeth. In
Fig. 54, a highly magnified view is given of a small portion of human dentine, showing the tubuli, in the intertubular substance, with the traces of the primitive cellular constitution of that substance. For the mode in
which the nucleated cells of the primary basis of the
tooth, called "tooth-pulp," are converted into dentine,
reference may be made to the author's " Odontography"
(Introd., plates 1 and 2). The tubuli, besides fulfilling
the mechanical ends above stated, receive the plasma
transuded from the remains of the vascular pulp, which




232      DEFINITION OF DENTAL TISSUES.
circulates, by anastomosing branches of the tubuli and
by the plasmatic cells of the intertubular substance,
through the dentine, maintaining a sufficient though
languid vitality of the tissue.  The delicate nervebranches on the pulp's surface, some minute production
Fig. 54.
SECTION OF HUMT3AN TOOTH (highly magnified).
of which may penetrate the tubuli, convey sensations of
impressions affecting the dentine-sensations of which
every one has experienced the acuteness when decay has
affected the dentine, or when mechanical or chemical
stimuli have " set the tooth on edge;" but true "dentine"
has no canals large enough to admit capillary vessels
with the red particles of blood.
The first modification of dentine is that in which capillary tracts of the primitive vascular pulp remain uncalcified, and permanently carry red blood into the substance
of the tissue. These so-called "vascular canals" present
various dispositions in the dentine which they modify,
and which modification is called "'vaso-dentine."  It is
often combined with true dentine in the same tooth, e.g.,




DEFINITION OF DENTAL TISSUES.           233
in the large incisors of certain rodents, the tusks of the
elephant, the molars of the extinct iguanodon.
A second modification of the fundamental tissue of the
tooth is where the cellular basis is arranged in concentric layers around the vascular canals, and contains
"radiated cells" like those of the osseous tissue; it is
called "osteo-dentine."  The transition from dentine to
vaso-dentine, and from this to osteo-dentine, is gradual,
and the resemblance of osteo-dentine to true bone is very
close.' Cement" always closely corresponds in texture with
the osseous tissue of the same animal; and wherever it
occurs of sufficient thickness, as upon the teeth of the
horse, sloth, or ruminant, it is also traversed, like bone,
by vascular canals. In reptiles and mammals, in which
the animal basis of the bones of the skeleton is excavated
by minute radiated cells, these are likewise present, of
similar size and form, in the cement, and are its chief
characteristic as a constituent of the tooth. The relative
density of the dentine and cement varies according to
the proportion of the earthy material, and chiefly of that
part which is combined with the animal matter in the
walls of the cavities, as compared with the size and number of the cavities themselves. In the complex grinders
of the elephant, the masked boar, and the capybara, the
cement, which forms nearly half the mass of the tooth,
wears down sooner than the dentine.
The "enamel" is the hardest constituent of a tooth,
and consequently the hardest of animal tissues; but it
consists, like the other dental substances, of earthy matter, arranged by organic forces in an animal matrix.
Here, however, the earth is mainly contained in the
canals of the animal membrane, and in mammals and
20*




234   CHEMICAL COMPOSITION OF TEETH.
reptiles, completely fills those canals, which are comparatively wide, whilst their parietes are of extreme tenuity.
CHEMICAL COMPOSITION OF TEETH.1
MAN.       LION.          OX.        CROCODILE. PIKE..0..              0...
Phosphate of lime
with a trace of flu-  66.72 89.82 60.03 83.33 59.57 81.86 58.73 53.69 53.39 63.98
ate of lime    )
Carbonate of lime    3.36  4.37  3.00  2.94  7.00  9.33  7.22  6.30  6.29  2.54
Phosphate ofmagnesia  1.08  1.34  4.21  3.70  0.99  1.20  0.99 10.22  9.99  0.73
Salts......  0.83  0.88  0.77  0.64  0.91  0.93  0.82  1.34  1.42  0.97
Chondrine...   27.61  3.39 31.57  9.39:30.71  6.66 31.31 27.66 28.15 30.60
Fat.....   0.40  0.20  0.42 trace  0.82  0.02  0.93  0.79  0.76  1.18
100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.0
The examples are extremely few, and, as far as I know,
are peculiar to the class Pisces, of calcified teeth, which
consist of a single tissue, and this is always a modification of dentine. The large pharyngeal teeth of the
wrasse (Labrus) consist of a very hard kind of dentine.
The next stage of complexity is where a portion of the
dentine is modified by vascular canals. Teeth, thus
composed of dentine and vasodentine, are very common
in fishes.
The hard dentine is always external, and holds the
place  and  performs  the  office  of enamel in the teeth of
higher animals. The grinding teeth of the dugong, and
the conical teeth of the great sperm whale, are examples
of teeth composed of dentine and cement, the latter tissue
forming a thick external layer.
In the teeth of the sloth, and its great extinct conge.
1 Selected from the analytic tables given in the author's'Odontography," 4to. vol. i. pp. lxii., lxiv. (1840.)




COMPLEX AND COMPOUND TEETH.              235
ner, the megatherium, the hard dentine is reduced to a
thin layer, and the chief bulk of the tooth is made up of
a central body of vaso-dentine, and a thick external crust
of cement. The hard dentine is, of course, the firmest
tissue of a tooth so composed, and forms the crest of the
transverse ridges of the grinding surface, like the enamel
plates in the elephant's grinder.
The human teeth, and those of the carnivorous mammals, appear at first sight to be composed
of dentine and enamel only; but their      Fig. 55.
crowns are originally, and their fangs
are always, covered by a thin coat of
cement. There is also commonly a small
central tract of osteo-dentine in old
teeth.
The teeth, called compound or complex, in mammalia, differ as regards their
composition from the preceding only by
the different proportion and disposition           i
of the constituent tissues. Fig. 55 is a
longitudinal section of the incisor of a
horse; d is the dentine, e the enamel, and
c the cement, a layer of which is reflected  /
into the deep central depression of the
crown; s indicates the colored mass of SECTION OF HORSE'S
INCISOR.
tartar and particles of food which fills up
the cavity, forming the "mark" of the horse-dealer.
A very complex tooth may be formed out of two tissues
by the way in which these may be interblended, as the
result of an original complex disposition of the constitu.
ents of the dental matrix.
Certain fishes, and a singular family of gigantic extinct
0           zn~~~~~c




236      COMPLEX AND COMPOUND TEETH.
batrachians, which T have called " Labyrinthodonts,"' exhibit, as the name implies, a remarkable instance of this
kind of complexity. The tooth appears to be of the
simple conical kind, with the exterior surface merely
striated longitudinally; but, on making a transverse section, as in Fig. 56, each streak is a fissure into which the
very thin external layer of cement, c, is reflected into the
body of the tooth, following the sinuous wavings of the
lobes of dentine, d, which diverge from the central pulp
cavity, a. The inflected fold of cement, c, runs straight
Fig. 56.
TRANSVERSE SECTION OF TOOTH OF LABYRINTHODON.
for about half a line, and then becomes wavy, the waves
rapidly increasing in breadth as they recede from the
periphery of the tooth; the first two, three, or four undulations are simple, then their contour itself becomes
broken by smaller or secondary waves; these become
stronger as the fold approaches the centre of the tooth,
I" Proceedings of the Geological Society," Jan. 20, 1841, p. 257.




COMPLEX AND COMPOUND TEETH.              237
when it increases in thickness, and finally terminates by
a slight dilatation or loop close to the pulp-cavity, from
which the free margin of the inflected fold of cement is
separated by an extremely thin layer of dentine. The
number of the inflected converging folds of dentine is
about fifty at the middle of the crown of the tooth, but is
greater at the base. All the inflected folds of cement, at
the base of the tooth, have the same complicated disposition with increased extent; but, as they approach their
termination towards the upper part of the tooth, they also
gradually diminish in breadth, and consequently penetrate to a less distance into the substance of the tooth.
Hence, in such a sectiorp as is delineated (Fig. 56), it will
be observed that some of the convoluted folds, as those
marked cc, extend near to the centre of the tooth; others, as
those marked c', reach only about half-way to the centre;
and those folds, c", which, to use a geological expression,
are "' cropping out," penetrate to a very short distance'into
the dentine, and resemble, in their extent and simplicity,
the converging folds of cement in the fangs of the tooth
of the ichthyosaurus.
The disposition of the dentine, d, is still more complicated than that of the cement. It consists of a slender,
central, conical column, excavated, by a conical pulpcavity, a, for a certain distance from the base of the tooth;
and this column sends from its circumference, radiating
outwards, a series of vertical plates, which divide into
two, once or twice, before they terminate at the periphery
of the tooth. Each of these diverging and dichotomizing
plates gives off; throughout its course, smaller processes,
which stand at right angles, or nearly so, to the main
plate. They are generally opposite, but sometimes alternate; many of the secondary plates or processes, which are




238     COMPLEX AND COMPOUND TEETH.
given off near the centre of the tooth, also divide into two
before they terminate, as at n; and their contour is seen,
in the transverse section, to partake of all the undulations
of the folds of cement which invest them, and divide the
dentinal plates and processes from each other.
Another kind of complication is produced by an aggregation of many simple teeth into a single mass.
The examples of these truly compound teeth are most
common in the class of fishes; but the illustration here
selected is from the mammalian class. Each tooth of the
Cape ant-eater (Orycteropus), preFig. 57.      sents a simple form, is deeply
set in the jaw, but without divid12d  - ing into fangs; its broad and flat
~s    |    _I"~    base is porous, like the section of
a common cane. The canals to
which these pores lead, contain
processes of a vascular pulp, and
are the centres of radiation of as
many independent series of dend   tinal tubules. Each tooth, in fact,
consists of a congeries of long and
slender prismatic denticles of denTRANSVERSE SECTION OF PART tine, which are cemented together
OF TOOTH OF Orycteropue by their ossified capsules, the co(magnified).   lumnar denticles slightly decreasing in diameter, and occasionally bifurcating as they
approach the grinding surface of the tooth. Fig. 57 gives
a magnified view of a portion of the transverse section of
the fourth molar, showing c, the cement; d, the dentine;
and p, the pulp-cavity of the denticles.
In the elephant, the denticles of the compound molars
are in the form of plates, vertical to the grinding surface




COMPLEX AND COMPOUND TEETH.                  239
and transverse to the long diameter of the tooth.  When
the tooth is bisected vertically and lengthwise, the three
substances, d, dentine, e, enamel, and c, cement, are seen
interblended, as in Fig. 58, in which p is the common
pulp-cavity, and r one of the roots of this complex tooth.
Such are some of the prominent features of a field of
Fig. 58.
LONGITUDINAL SECTION OF PART OF GRINDEI' OF ELEPHLANT.
observation which Comparative Anatomy opens out to
our view-such the varied nature, and such the gradation
of complexity of the dental tissues, which, up to December,
1839, continued, notwithstanding successive approximations to the truth, to be described, in systematic works,
as a "phaneros," or "a dead part or product, exhaled
from the surface of a formative bulb!"
I See the Fasciculus of AM. de Blainville's great work, " Ostdographie
et Odontographie d'Aninlaux Vertlbr6s," which he submitted to the




240           DENTAL SYSTEM OF FISHES.
DENTAL SYSTEM OF FISHIES.
The teeth of fishes, whether we study them in regard
to their number, form, substance, structure, situation, or
mode of attachment, offer a greater and more striking
series of varieties than do those of any other class of animals.
As to number, they range from  zero to countless quanFig. 59.
SKULL OF THE PIKE, SHOWING THE TEETI.
tities.  The lancelet, the  ammocete, the sturgeon, the
paddle-fish, and the whole order of lephobranchii, are edenAcademy of Sciences of the Institute of France on the same day, December 16, 1839, on which I communicated, on the occasion of my election
as correspondcling member of that body, my "Theory of the develop1ment
of dentine by centripetal calcification and conversion of the cells of the
pulp."




DENTAL SYSTEM  OF FISHIES.              241
tulous.  The rnyxinoids have a single pointed tooth on
the roof of the mouth, and two serrated dental plates on
the tongue. The tench has a single grinding tooth on
the occiput, opposed to two dentigerous pharyngeal jaws
below. In the lepidosiren, a single maxillary dental plate
is opposed to a single mandibular one, and there are two
small denticles on the nasal bone. In the extinct sharks
with crushing teeth, called ceratodus and tenodus, the jaws
were armed with four teeth, two above and two below.
In the hiircera, two mandibular teeth are opposed to four
maxillary teeth. From this low point the number in
different fishes is progressively multiplied, until, in the
pike (Fig. 59), the siluroids, and many other fishes, the
mouth becomes crowded with countless teeth.
With respect to form, it may be premised that, as organized beings withdraw themselves more and more, in
their ascent in the scale of life, from the influence of the
general polarizing forces, so their parts progressively deviate from geometrical figures; it is only, therefore, in the
lowest vertebrated class that we find teeth in the form of
perfect cubes, and of prisms or plates with three sides (as
in mnyletes), four sides (as in scarus), five or six sides (as in
myliobates, Fig. 60). The cone is the most common form
in fishes; such teeth may be slender, sharp-pointed, and
so minute, numerous, and closely aggregated, as to resemble the plush or pile of velvet. These are called
"villiform  teeth" (dentes villjformes, Lat.; dents en velours,
Fr.). All the teeth of the perch are of this kind.  When
the teeth are equally fine and numerous, but longer, these
are called " ciliiform" (dentes cilijiormes); when the teeth
are similar to but rather stronger than these, they are
called "setiform" (dentes setiformes, Lat.; dents en brosse,
Fr.); the teeth in the upper jaw of the pike (Fig. 59) are
21




242         DENTAL SYSTEM  OF FISHES.
of this kind. Conical teeth, as close-set and sharp-pointed
as the villiforme teeth, but of larger size, are called " raspteeth" (dentes raduliformes, Lat.; dents en rape, or en cardes,
Fr.); the pike presents such teeth on the back part of the
vomer.  The teeth of the sheat-fish (Silurus glanis) present
Fig. 60.
JAWS AND TEETH OF THE STING-RAY (M2yliobates).
all the gradations between the villiform  and raduliform
types. Setiform teeth are common in the fishes thence
called Chsetodonts; in the genus Citharince they bifurcate
at their free extremities; in the genus Platax they end
there in three diverging points, and the cone here merges
into the long and slender cylinder.  Sometimes the cone
is compressed into a slender trenchant blade: and this
may be pointed and recurved, as in the murcena; or
barbed, as in trichiurus and some other Scomberoides; or
it may be bent upon itself, like a tenter-hook, as in the
fishes thence called Goniodonts.  In the bonito may be
perceived a progressive thickening of the base of the
conical teeth; and this being combined in other predatory
fishes with increased size and recurved direction, they
then resemble the laniary or canine teeth of carnivorous
quadrupeds, as we see in the large teeth of the pike (Fig.
59), in the lophius, and in certain sharks.




DENTAL SYSTEM  OF FISHES.             243
The anterior diverging grappling teeth of the wolf-fish
(Fig. 61), i, form stronger cones; and by progressive
blunting, flattening, and expansion of the apex, observable in different fishes, the cone gradually changes to the
thick and short cylinder, such as is seen in the back teeth
of the wolf-fish, m, and in similar grinding and crushing
teeth in other genera, whether the fishes be feeders on
sea-weeds, or on crustaceous and testaceous animals. The
grinding surface of these short cylindrical teeth may be
convex, as in the sheep's-head fish (Sargus); or flattened,
as in the pharyngeal teeth of the wrasse (Labrus). Sometimes the hemispheric teeth are so numerous, and spread
over so broad a surface, as to resemble a pavement, as in
the pharyngeal bones of the wrasse; or they may be so
small, as well as numerous, as to give a granulated surface to the part of the mouth to which they are attached,
when they are called, in ichthyology, dentes graniformes.
A progressive increase of the transverse over the vertical diameter may be traced in the molar teeth of different fishes, and sometimes in those of the same individual,
as in labrus, until the cylindrical form is exchanged for
that of the depressed plate. Such dental plates (dentes
lamelliformes) may be formed not only circular, but elliptical, oval, semilunar, sigmoid, oblong, or even square,
hexagonal, pentagonal, or triangular; and the grinding
surface may present various and beautiful kinds of sculpturing. The broadest and thinnest lamelliform teeth are
those that form the complex grinding tubercle of the
diodon.
In the sharks and rays, the teeth are supported by the
upper and lower jaws, as in most quadrupeds; but many
other fishes have teeth growing from the roof of the
mouth, from the surface of the tongue, from the bony




244         TEETHI OF THE WOLF-FISH.
hoops or arches supporting the gills, and some have them
developed from the bone of the nose and the base of the
skull. In the carp and tench the teeth are confined to
this latter unusual position, and to a pair of bones, called
"pharyngeal," which circumscribe the back outlet of the
mouth. -
Fishes exhibit, moreover, a greater range of variety in
the mode of attachment of the teeth than any other class
of animals. In the sharks, and the singular fish called
the "angler," the teeth are movable, their base being tied
by ligaments to the jaw. In the angler the ligaments are
so inserted that they do not permit the teeth to be bent
outwards beyond the vertical position, but yield to pressure in the contrary direction, by which the point of the
tooth may be directed towards the back of the mouth;
the instant, however, that the pressure is remitted, the
tooth returns through the elasticity of the bent ligaments,
as by the action of a spring, to its usual erect position;
the deglutition of the prey of this voracious fish is thus
facilitated, and its escape prevented.  The broad and
generally bifurcate bony base of the teeth of sharks is
attached by ligaments to the semi-ossified crust of the
cartilaginous jaws; but they have no power of erecting
or depressing the teeth at will.
The teeth of the sphyrsena are examples of the ordinary
implantation in sockets, with the addition of a slight anchylosis of the base of the fully-formed tooth with the
alveolar walls; and the compressed rostral teeth of the
saw-fish are deeply implanted in sockets; the hind
margin of their base is grooved, and a corresponding
ridge from the back part of the socket fits into the groove,
and gives additional fixation to the tooth.
The singular and powerfully developed dental system




TEETH OF THE WOLF-FISH.              245
of the wolf-fish (Anarrhicas lupus, Fig. 61) has been a subject of interest to many anatomists. Most of the teeth
are powerful crushers; some present the laniary type,
with the apices more or less recurved and blunted by use,
and consist of strong cones, spread abroad, like grapplinghooks, at the anterior part of the mouth, i, i.
The premaxillary teeth, 22, i, are all conical, and arranged in two rows; there are two, three, or four in the
exterior row, at the mesial half of the bone, which are the
largest; and from six to eight smaller teeth are irregularly arranged behind.  There are three large,-strong,
diverging laniaries at the anterior end of each premandibular bone, and immediately behind these an irregular
number of shorter and smaller conical teeth, which gradually exchange this form for that of large obtuse tubercles, m, m; these extend backwards, in a double alternate
series, along a great part of the alveolar border of the
bone, and are terminated by two or three smaller teeth
in a single row, the last of which again presents the conical form. Each palatine bone, 20, supports a double row
of teeth, the outer ones being conical and straight, and
from four to six in number; the inner ones two, three, or
four in number, and tuberculate. The lower surface of
the vomer, 13, is covered by a double irregularly alternate series of the same kind of large tuberculate crushing
teeth as those at the middle of the premandibular bone.
Thus the inside of the mouth appears to be paved with
teeth, by means of which the wolf-fish can break in pieces
the shells of whelks and lobsters, and effectually disengage the nutritious animal parts from them. All the
teeth are anchylosed to more or less developed alveolar
eminences of bones. From the enormous power of the
muscles of the jaws, and the strength of the shells which
21*




246         TEETII OF THE WOLF-FISH.
are cracked and crushed by the teeth, their fracture and
displacement must obviously be no unfrequent occurc;Fq
I  I 1
rence; and most specimens of the jaws of the wolf-fish
exhibit some of the teeth either separated at this line of
imperfect anchylosis, or, more rarely, detached by fracture of the supporting osseous alveolar process.
Thus, with reference to the main and fundamental tissue of tooth, we find not fewer than six leading modifications in fishes.




TISSUE OF TOOTH IN FISHES.           247
Hard or true dentine —Sparoids, labroids, lophius,
balistes, pycnodonts, prionodon, sphyr'ena, megalichthys,
rhizodes, diodon, scarus;
Osteodentine-Cestracion, acrodus, lepidosiren, ctenodus, hybodus, percoids, scisenoids, cottoids, gobioids,
sharks, and many others;
Vasodentine-Psammodus, chimseroids, pristis, myliobates;
Plicidentine-Lophius, holoptychius, bothriolepis; and
Dendrodentine-Dendrodus;
Besides the compound teeth of the scarus and diodon.
One structural modification may prevail in some teeth,
another in other teeth, of the same fish; and two or more
modifications may be present in the same tooth, arising
from changes in the process of calcification and a persistency of portions or processes of the primitive vascular
pulp or matrix of the dentine.
The dense covering of the beak-like jaws of the parrotfishes (Scari) consists of a stratum of prismatic denticles,
standing almost vertically to the external surface of the
jaw bone; this peculiar armature of the jaws is adapted
to the habits and exigences of a tribe of fishes which
browse upon the lithophytes that clothe, as with a richly
tinted carpet, the bottom of the sea, just as the ruminant
quadrupeds crop the herbage of the dry land.
The irritable bodies of the gelatinous polypes, which
constitute the food of these fishes, retreat, when touched,
into their star-shaped stony shells, and the scari consequently require a dental apparatus strong enough to
break off or scoop out these calcareous recesses. The
jaws are, therefore, prominent, short, and stout, and the
exposed portions of the premaxillaries and premandibulars are incased by a complicated dental covering. The




248     TEETH OF THE BARRACUDA FISH.
polypes and their cells are reduced to a pulp by the action
of the pharyngeal jaws and teeth that close the posterior
aperture of the mouth.
There is a close analogy between the dental mass of
the scarus and the complicated grinders of the elephant,
both in form, structure, and in the reproduction of the
component denticles in horizontal succession. But in the
fish, the complexity of the triturating surface is greater
than in the mammal, since, from the mode in which the
wedge-shaped denticles of the scarus are implanted upon,
and anchylosed to, the processes of the supporting bone,
this likewise enters into the formation of the grinding
surface when the tooth is worn down to a certain point.
The proof of the efficacy of the complex masticatory
apparatus above described, is afforded by the contents of
the alimentary canal of the scari. Mr. Charles Darwin,
the accomplished naturalist and geologist, who accompanied Captain Fitzroy, R. N., in the circumnavigatory
voyage of the Beagle, dissected several parrot-fishes
soon after they were caught, and found the intestines
laden with nearly pure chalk, such being the nature of
their excrements; whence he ranks these fishes among
the geological agents to which is assigned the office of
converting the skeletons of the lithophytes into chalk.
The most formidable dentition exhibited in the order of
osseous fishes is that which characterizes the sphyraena,
and some extinct fishes allied to this predatory genus.
In the great barracuda of the southern shores of the
United States (Sphyrcena barracuda, Cuv.), the lower-jaw
contains a single row of large, compressed, conical, sharppointed, and sharp-edged teeth, resembling the blades of
lancets, but stronger at the base; the two anterior of
these teeth are twice as long as the rest, but the posterior




TEETH OF TIlE BARRACUDA FISH.    249
and serial teeth gradually increase in size towards the
back part of the jaw; there are about twenty-four of these
piercing and cutting teeth in each premandibular bone.
They are opposed to a double row of similar teeth in the
upper-jaw, and fit into the interspace of these two rows
when the mouth is closed. The outermost row is situated
on the intermaxillary, the innermost on the palatine
bones; there are no teeth on the vomer or superior maxillary bones. The two anterior teeth in each premaxillary bone equal the opposite pair in the lower-jaw in
size; the posterior teeth are serial, numerous, and of small
size; the second of the two anterior large premaxillary
teeth is placed on the inner side of the commencement of
the row of small teeth, and is a little inclined backwards.
The retaining power of all the large anterior teeth is increased by a slight posterior projection, similar to the barb
of a fish-hook, but smaller. The palatine bones contain
each nine or ten lancet-shaped teeth, somewhat larger
than the posterior ones of the lower-jaw. All these teeth
afford good examples of the mode of attachment by implantation in sockets, which has been denied to exist in
fishes.
The loss or injury to which these destructive weapons
are liable, in the conflict which the sphyrmena wages with
its living and struggling prey, is repaired by an uninterrupted succession of new pulps _and teeth. The existence
of these is indicated by the foramina, which are situated
immediately posterior to, or on the inner margin of, the
sockets of the teeth in place; these foramina lead to alveoli
of reserve, in which the crowns of the new teeth in different stages of development are loosely imbedded. It is
in this position of the germs of the teeth that the sphyrenoid fishes, both recent and fossil, mainly differ, as to their




250    DENTAL REPRODUCTION IN FISHES.
dental characters, from the rest of the scomberoid family,
and proportionally approach the sauroid type.
In all fishes the teeth are shed and renewed, not once
only, as in mammals, but frequently during the whole
course of their lives. The maxillary dental plates of
lepidosiren, the cylindrical dental masses of the chimoeroid
and edaphodont fishes, and the rostral teeth of the sawfish (if these modified dermal spines may be so called) are,
perhaps, the sole examples of "permanent teeth" to be
met with in the whole class. In the great majority of
fishes, the germs of the new teeth are developed like those
of the old, from the free surface of the buccal membrane
throughout the entire period of succession; a circumstance
peculiar to the present class. The angler, the pike, and
most of our common fishes, illustrate this mode of dental
reproduction; it is very conspicuous in the cartilaginous
fishes (Fig. 60, e. g.), in which the whole phalanx of their
numerous teeth is ever marching slowly forwards in rotatory progress over the alveolar border of the jaw, the
teeth being successively cast off as they reach the outer
margin, and new teeth rising from the mucous membrane
behind the rear rank of the phalanx.
This endless succession and decadence of the teeth, together with the vast number in which they often coexist
in the same fish, illustrate the law of "vegetative or irrelative repetition," as it manifests itself on the first introduction of new organs in the animal kingdom, under
which light we must view the above-described organized
and calcified preparatory instruments of digestion in the
lowest class of the vertebrate series.




DENTAL SYSTEM OF REPTILES.           251
DENTAL SYSTEM  OF REPTILES.
In the class reptilia an entire order (Chelonia), including
the tortoises, terrapenes, and turtles, are devoid of teeth;
but the jaws in these edentulous reptiles are covered by a
sheath of horn, which in some species is of considerable
thickness and density; its working surface is trenchant in
the carnivorous species, but is variously sculptured and
adapted for both cutting and bruising in the vegetable
feeders. No species of toad possesses teeth; neither have
the jaws the compensatory covering above described in
the chelonians. Frogs have teeth in the upper but not
in the lower jaw. Newts and salamanders have teeth in
both jaws, and also upon the palate; and teeth are found
in the latter situation as well as on the jaws in most serpents and in the iguana lizard. In most other lizards and
in crocodile's, the teeth are confined to the jaws: in the
former they are cemented or anchylosed to the jaw; in
the latter they are implanted in sockets.
The existing lizards exhibit many modifications in the
form of the teeth, according to the nature of the food.
They are pointed with sharp cutting edges in the great
carnivorous monitor (Varanus), and are obtuse and
rounded like paving-stones in the herbivorous or mixed
feeding scinks, called, on account of the shape of the
teeth, cyclodus.  The gigantic extinct lizards showed
similar modifications of their teeth. The megalosaurus
had teeth which combined the properties of the knife,
the sabre, and the saw (Fig. 62). When first protruded
above the gum, the apex of the tooth presented a double
cutting edge of serrated enamel; its position and line of




252       DENTAL SYSTEM OF REPTILES.
action were nearly vertical, and its form, like that of the
two-edged sword, cutting equally on
Fig. 62.     each side. As the tooth advanced in
growth, it became curved backwards
in the form of a pruning-knife, and
the edge of serrated enamel was continued downwards to the base of the
concave and cutting side of the tooth;
whilst on the other side a similar
edge descended but a short distance
from the point, and the convex part
of the tooth became blunt and thick,
as the back of a knife is made thick
for the purpose of producing strength.'In a tooth thus formed for cutting
along its concave edge, each moveTOOF — EA-   ment of the jaw combined the power
TOOTH OF THE MIEGALOSAURTUS.     of the knife and the saw. The backward curvature of the full-grown
teeth enables them to retain, like barbs, the prey which
they had penetrated.
In the iguanodon —the gigantic contemporary of the
megalosaurus —the crown of
Fig. 63.       the teeth (Fig. 63)was so shaped
j.  /~ ~? that, after the apex became
worn  down, it presented a
11/9   broad and nearly horizontal
surface, exposing dental substances of four. different degrees of density, viz: a ridge
of enamel along the outer border of the crown; a layer of
NEW-FORMED AND WOR TEETunvscular  dentineOF
THE IGUANODON.     hard  or unvascular dentine




DENTAL SYSTEM OF REPTILES.            253
next to this; a layer of softer vascular dentine forming
the inner half of the crown; and a portion of firm osteodentine in the middle of the grinding surface, formed by
the ossified remnant of the tooth-pulp.  The series of
complex teeth, so constructed, seems to have been admirably adapted to the cropping and comminution of such
tough vegetable food as the clathrarice and similar now
extinct plants, the fossil remains of which are found
buried with those of the iguanodon. No existing reptile
now presents so complicated a structure of the tooth in
relation to vegetable food. The still more complex, and
indeed marvellous structure of the teeth of the extinct
gigantic lizard-like toad, called Labyrinthodon, has been
already noticed (Fig. 56, p. 236). But, perhaps, the most
singular dental structure yet found in the ancient members of the class Reptilia, is that presented by certain
species of fossil found in South Africa, and probably
from a geological formation nearly as old as our coal
strata.  I have called them "Dicynodonts," from their
dentition being reduced to one long and large canine
tooth on each side of the upper jaw. As these teeth give,
at first sight, a character to the jaws like that which the
long poison-fangs give, when erected, to the jaws o-f the
rattlesnake, I shall briefly notice their characters before
entering upon the description of the more normal saurian
dentition.
Fig. 64 gives a reduced side view of the skull and
teeth of the Dicyiiodon lacerticeps.
The maxillary bone, 21, is excavated by a wide and
deep alveolus, with a circular area of half an inch, and
lodges a long and strong, slightly curved, and sharppointed canine tooth or tusk, which projects about twothirds of its length from the open extremity of the socket.
22




254           TEETHI OF DICYNODON.
The direction of the tusks is forwards, downwards, and
very slightly inwards; the two converging in the descent
Fig. 64.
SKULL AND TUSKS OF Dicynodon lacerticcps.
along the outer side of the compressed symphysis of the
lower jaw, cc. The tusk is principally composed of a
body of compact unvascular dentine. The base is excavated by a wide conical pulp-cavity, p, with the apex
extending to about one-half of the implanted part of the
tusk, and a linear continuation extending along the centre
of the solid part of the tusk.
Until the discovery of the rhynchosaurus, this edentuIous and horn-sheathed condition of the jaws was supposed
to be peculiar to the chelonian order among reptiles; and
it is not one of the least interesting features of the dicynodonts of the African sandstones, that they should repeat
a chelonian character hitherto peculiar amongst lacertians,
to the above-cited remarkable extinct edentulous genus
of the new red sandstone of Shropshire; but, our interest
rises almost to astonishment when, in a saurian skull, we
find, superadded to the horn-clad mandibles of the tortoise, a pair of tusks, borrowed, as it were, from the mammalian class, or rather foreshadowing a structure which,




TEETH OF CROCODILES.                255
in the existing creation, is peculiar to certain members of
the highest organized warm-blooded animals.
In the other reptilia, recent or extinct, which most
nearly approach the mammalia in the structure of their
teeth, the difference characteristic of the inferior and
cold-blooded class is manifested in the shape, and in the
system of shedding and succession of the teeth; the base
of the implanted teeth seldom becomes consolidated,
never contracted to a point, as in the fangs of the simple
teeth of mammalia, and at all periods of growth one or
more genus of teeth are formed within or near the base
of the tooth in use, prepared to succeed it, and progressing
towards its displacement. The dental armature of the
jaws is kept in serviceable order by uninterrupted change
and succession; but the forming organ of the individual
tooth is soon exhausted, and the life of the tooth itself
may be said to be comparatively short.
If one of the conical, sharp-pointed, and two-edged
teeth of the Gangetic crocodile, called "garrhial," by the
Hindoos, be extracted, its base will be found hollow, and
Fig. 65.
TOOTH, WITH GERMS OF SUCCESSORS, OF THE GARRHIAL (Gavialis gangeticu8).




256       TEETH OF POISONOUS SNAKES.
partly absorbed or eaten away, as at a, Fig. 65; and
within the cavity will be seen the half-formed succeeding
tooth, b; at the base of which may probably be found the
beginning or germ, c, of the successor of that tooth; all
the teeth in the crocodile tribe being pushed out and replaced in the vertical direction by new teeth, as long as
they live. The individual teeth inucrease in size as the
animal grows; but the number of teeth remains the same
from the period when the crocodile quits the egg to the
attainment of its full size and age. No sooner has the
young tooth penetrated the interior of the old one, than
another germ begins to be developed from the angle between the base of the young tooth and the inner alveolar
process, or in the same relative position as that in which
its immediate predecessor began to rise; and the processes
of succession and displacement are carried on, uninterruptedly, throughout the long life of these cold-blooded
carnivorous reptiles.  The fossil jaws of the extinct
crocodiles demonstrate that the same law regulated the
succession of the teeth at the ancient epochs when they
prevailed in greatest numbers, and under the most variel
specific modifications, as at the present day, when they
are reduced to a single family.
The most complex condition of the dental system in
the reptile class is that which is presented by the poisonous serpents, in which certain teeth are associated with
the tube or duct of a poison-bag and gland.
These teeth, called "poison-fangs," are confined to those
bones of the upper jaw called "maxillary," and are
usually single; or, when more, one only is connected
-with the.poison-apparatus, and the others are either
simple teeth, or preparing to take the, place of the poison-fang.




TEETH OF POISONOUS SNAKES.              257
To give an idea of the structure of this   Fig. 66.
tooth, we may suppose a simple slender          A
tooth, like that of a boa-constrictor, to be
flattened, and its edges then bent towards
each other and soldered together so as to
form a tube, open at both ends, and inclosing
the end of the poison-duct. Such a tooth is
represented at Fig. 66, where A is the oblique
opening penetrated by the duct, and v the
narrower fissure by which the venom escapes.
The duct which conveys the poison, although it runs through the centre of the  POISON-FANG
tooth, is really on the outside of the tooth.  OF RATTLESNAKE (magThe bending of the dentine about it begins    nified).
a little beyond the base of the tooth, where
the poison-duct rests in a slight groove or longitudinal
indentation on the convex side of'the fang; as it proceeds, it sinks deeper into the substance
of the tooth, and the sides of the groove  Fig. 67.
meet and seem to coalesce, so that the,
trace of the inflected fold ceases, in some
species, to be perceptible to the naked
eye; and the fang appears, as it is comrn
monly described, to be perforated by
the duct of the poison!gland.
In the viper, the line of union may
be seen as marked at v, Fig. 66; and 
when such a tooth is carefully divided
lengthwise, as in Fig. 67, the true pulp.
cavity in the substance of the tooth is
seen, as at p,p, to terminate in a point;
and the poison-canal, as at u, v, to run  SECTION OF A POISONalong the forepart of the singularly  FANG-RATTLESNAKE.
22*




258      DENTAL SYSTEM OF MA'MMALIA.
modified tooth. This tooth is soldered to the maxillary
bone (Fig. 68), which rotates so as to keep the tooth laid
flat in the mouth at ordinary times, and to erect it when
the deadly blow is about to be
Fig. 68.       struck. The head of the snake
28                  is raised, drawn back, and the
21  fings, erect, and exposed by the
widely open mouth, are struck,
by the force of the powerful
SKULL OF A RATTLESNAKE    muscles of the head and neck,
(Crotalus horridus).  into the surface aimed at, the
poison-bags at the same inoment are squeezed, and their contents driven through the
canal in the tooth into the wound. And here may be
noticed the advantage of having the solid point of the
tooth prolonged beyond the outlet of the poison-canal,
and not weakened by its continuation to the apex.
DENTAL SYSTEM OF MAMMALS.
The class iammalia, like those of Reptilia and Pisces,
includes a few genera and species that are devoid of
teeth; the true ant-eaters (myrmnecophaga), the scaly anteaters or pangolins (manis), and thIe spiny monotrematous
ant-eater (echidna), are examples of strictly edentulous
mammals. The ornithorhynchus has horny teeth, and
the whales (balcena and balcenoptera) have transitory embryonic calcified teeth, succeeded by whalebone substitutes in the upper jaw.
The female narwhal seems to be edentulous, but has
the germs of two tusks in the substance of the upper
jaw-bones; one of these becomes developed into a large




DENTAL SYSTEM OF MAMMALIA.           259
and conspicuous weapon in the male narwhal, whence the
name of its genus, of monodon, meaning single tooth. In
another cetacean, the great bottle-nose or hyperoodon, the
teeth are reduced in the adult to two in number, whence
the specific name II. bidens, but they are confined to the
lower jaw.
The elephant has never more than one entire molar, or
parts of two, in use on each side of the upper and lower
jaws; to which are added two tusks, more or less developed, in the upper jaw.
Some rodents, as the Australian water-rats (Hydronys),
have two grinders on each side of both jaws; which,
added to the four cutting-teeth in front, make twelve in
all; the common number of teeth in this order is twenty,
but the hares and rabbits have twenty-eight each.
The sloth has eighteen teeth. The number of teeth,
thirty-two, which characterizes man, the apes of the old
world, and the true ruminants, is the average one of the
class mammalia; but the typical number is forty-four.
The examples of excessive number of teeth are presented in the order Bruta, by the priodont armadillo,
which has ninety-eight teeth; and in the cetaceous order
by the cachalot, which has upwards of sixty teeth, though
most of them are confined to the lower jaw; by the common porpoise, which has between eighty and ninety teeth;
by the Gangetic dolphin, which has one hundred and
twenty teeth; and by the true dolphins (delphinus), which
have from one hundred to one hundred and ninety teeth,
yielding the maximum number in the class Mammalia.
FoRM.-Where the teeth are in excessive number, as
in the species above cited, they are small, equal, or subequal, and usually of a simple conical form.
In most other mammalia, particular teeth have special




260   CHARACTERS OF MAMMALIAN TEETHI.
forms for special uses: thus, the front teeth, from being
commonly adapted to effect the first coarse division of
the food, have been called cutters or incisors; and the
back teeth, which complete its comminution, grinders or
molars; large conical teeth situated behind the incisors,
and adapted by being nearer the insertion of the biting
muscles to act with greater force, are called holders,
tearers, laniaries, or, more commonly, canine teeth, from
being well developed in the dog and other carnivora.
Molar teeth, which are adapted for mastication, have
either tuberculate, or transversely ridged, or flat summits,
and usually are either surrounded by a ridge of enamel,
or are traversed by similar ridges arranged in various
patterns.
The large molars of the capybara and elephant have
the crown cleft into a numerous series of compressed
transverse plates, cemented together side by side.
The teeth of the mammalia have usually so much more
definite and complex a form than those of fishes and reptiles, that three parts are recognized in them, viz: the
"fang," the "neck," and the "crown."  The fang or root
(radix) is the inserted part; the crown (corona) the exposed part; and the constriction which divides these is
is called the neck (cervix).
FIXATION. —It is peculiar to the class mammalia to
have teeth implanted in sockets by two or more fangs;
but this can only happen to teeth of limited growth, and
generally characterizes the molars and premolars; perpetually growing teeth require the base to be kept simple
and widely excavated for the persistent pulp. In no
mammiferous animal does anchylosis of the tooth with the
jaw constitute a normal mode of attachment. Each tooth
has its particular socket, to which it firmly adheres by




CHARACTERS OF MAMMALIAN TEETH.   261
the close coadaptation of their opposed surfaces, and by
the firm adhesion of the alveolar periosteum to the organized cement which invests the fang or fangs of the tooth.
True teeth implanted in sockets are confined, in the
mammalian class, to the maxillary, premaxillary, and
mandibular, or lower maxillary bones, and form a single
row in each. They may project only from the premaxillary bones, as in the narwhal, or only from the lower
maxillary bone, as in ziphius; or be apparent only in the
lower maxillary bone, as in the cachalot; or be limited to
the superior and inferior maxillaries, and not present in
the premaxillaries, as in the true peccora (cow, sheep),
and most bruta (sloth, armadillo) of Linnmeus. In general,
teeth are situated in all the bones above mentioned. In
man, where the premaxillaries early coalesce with the
maxillary bones, where the jaws are very short, and the
crowns of the teeth are of equal length, there is no vacant
space in the dental series of either jaw, and the teeth derive some additional fixity by their close apposition and
mutual pressure. N'o inferior mammal now presents this
character; but its importance, as associated with the
peculiar attributes of the human organization, has been
somewhat diminished by the discovery of a like contiguous arrangement of the teeth in the jaws of a few extinct
quadrupeds, e. g. anoplotherium, nesodon, and dichodon.
STRUCTURE.-The teeth of the mammalia usually consist of hard unvascular dentine, defended at the crown by
an investment of enamel, and everywhere surrounded by
a coat of cement. The coronal cement is of extreme
tenuity in man, quadrumana, and the terrestrial carnivora;
it is thicker in the herbivora, especially in the complex
grinders of the elephant. Vertical folds of enamel and
cement penetrate the crown of the tooth in the ruminants,




262   DEVELOPMENT OF MAMMALIAN TEETH.
and in most rodents and pachyderms, characterizing by
their varions forms the genera of the last two orders.
The teeth of the sloths, armadillos, and sperm-whales
have no true enamel. The tusks of the narwhal, walrus,
and elephant consist of modified dentine, which in the
last great proboscidian animal is properly called "ivory,"
and is covered by cement.
The forming-organ of a mammalian tooth consists, as
in the lower classes, of a pulp and a capsule. The substance of the pulp is converted into the " dentine;" that
of the capsule into the "cement."  Where enamel is to
be added, a peculiar organ is formed on the inner surface
of the capsule, which arranges the hardening material
into the form, and of the density, characteristic of enamel.
This substance is so hard in the tooth of the hippopotamus, as to "strike fire" like flint with steel. The whole
forming-organ is called "matrix."
The matrix of certain teeth does not give rise during
any period of their formation to the germ of a second
tooth, destined to succeed the first; this tooth, therefore,
when completed and worn down, is not replaced. The
sperm whales, dolphins, and porpoises are limited to this
simple provision of teeth. In the armadillos and sloths,
the want of germinative power, as it may be called, in
the matrix is compensated by the persistence of the matrix, and by the uninterrupted growth of the teeth.
In most other mammalia, the matrix of the first developed tooth gives origin to the germ of a second tooth,
which sometimes displaces the first, sometimes takes its
place by the side of the tooth from which it has originated.
Al those teeth which are displaced by their progeny are
called temporary, deciduous, or milk teeth; the mode and
direction in which they are displaced and succeeded, viz:




DEVELOPMENT OF MAMMALIAN TEETH.  263
from above downwards in the upper, from below upwards
in the lower jaw: in both jaws vertically-are the same
as in the crocodile; but the process is never repeated more
than onzce in any mammiferous animal. A  considerable
proportion of the dental series is thus changed; the
second or permanent teeth having a size and form as
suitable to the jaws of the adult as the displaced temporary teeth were adapted to those of the young animal.
The permanent teeth, which assume places not previously occupied by deciduous ones, are always the most
posterior in their position, and generally the most complex in their form.
The term  "molar," or "true molar," is restricted to
these teeth; the teeth between them and the canines are
called "premolars;" they push out the milk-teeth that
precede them, and are usually of smaller size and simpler
form than the true molars. They are called "bicuspids"
in human anatomy.
Fig. 69.
JAMWS AND TEETH OF TIlE LION.
Thus the class mammalia, in regard to the times of
formation and the succession of their teeth, have been




264            TEETH OF CARNIVORA.
divided into two groups: the monophyodonts,' or those
that generate a single set of teeth; and the diphyodonts,2
or those that generate two sets of teeth.
I proceed next to notice the principal modifications of
the teeth, as they are adapted to carnivorous, herbivorous,
or mixed feeding habits in the diphyodont mammalia.
The lion may be taken as the type of the flesh-feeders
(Fig. 69).
The largest and most conspicuous teeth in this and
other feline quadrupeds are the "canines," c; they are of
great strength, deeply implanted in the jaw, with the fang
thicker and longer than the enamelled crown: this part
is conical, slightly recurved, sharp-pointed, convex in
front, almost flat on the inner side, and with a sharp
edge behind. The lower canines pass in front of the
upper ones when the mouth is closed.
The incisors, six in number on both jaws, form a transverse row; the outermost above, i, is the largest, resembling a small canine: the intermediate ones have broad
and thick crowns indented by a transverse cleft.
The first upper premolar, p 2, is rudimental: there is
no answerable tooth in the lower jaw. The second, p 3,
in both jaws has a strong conical crown supported on two
fangs. The third upper tooth, p4, has a cutting or
trenchant crown, divided into three lobes, the last being
the largest, and with a flat inner side, against which the
cutting tooth, m 1, in the lower jaw works, like a scissorblade. Behind, and on the inner side of the upper tooth,
p 4, there is a small tubercular tooth, m 1. A glance at
the long and strong, sub-compressed, trenchant, and
sharp-pointed canines, suffices to appreciate their pecufroAQVo, once: pswa, I generate; osov;, tooth.
2 &C, twice; fun and ohoLv.




TEETHi OF CARNIVORA.              265
liar adaptation to seize, to hold, to pierce and lacerate a
struggling prey. The jaws are strong, but shorter than
in other carnivora, and with a concomitant reduction in
the number of the teeth: thus, the canines are brought
nearer to the insertion of the very powerful' biting muscles (called "temporal" and "masseter"), which work
them with proportionally greater force. The use of the
small pincer-shaped incisor teeth is to gnaw the soft
gristly ends of the bones, and to tear and scrape off the
tendinous attachments of the muscles and the periosteum.
The compressed trenchant blades of the sectorial teeth
play vertically upon each other's sides, likes the blades
of scissors, serving to cut and coarsely divide the flesh;
and the form of the joint of the lower jaw almost restricts its movement to the vertical direction, up and
down. The wide and deep zygomatic arches, and the
high crests of bone upon the skull, concur in completing
the carnivorous physiognomy of this most formidable of
the feline tribe.
The dentition of the hyena assumes those characteristics which adapt it for the peculiar food and habits of
the adult. The main modification is the great size and
strength of the molars as compared with the canines,
and more especially the thick and strong conical crowns
of the second and third premolars in both jaws, the base
of the cone being belted by a strong ridge which defends
the subjacent gum. This form of tooth is especially
adapted for gnawing and breaking bones, and the whole
cranium has its shape modified which work the jaws and
teeth in this operation.
The strength of the hyena's jaw is such that, in attacking a dog, he begins by biting off his leg at a single
snap.  Adapted, however, to obtain its food from the




266           TEETH OF CARNIVORA.
coarser parts of animals which are left by the nobler
beasts of prey, the hyena chiefly seeks the dead carcass,
and bears the same relation to the lion which the vulture
does to the eagle. The hyena cracks, crushes, and devours the bones as well as the softer parts of the animals
it preys upon. In consequence of the quantity of bones
which enter into its food, the excrements consist of solid
balls of a yellowish-white color, and of a compact
earthy fracture. Such specimens of the substance, known
in the old " Materia Medica" by the name of "album
grianum," were discovered by Dr. Bucklandr in the celebrated ossiferous cavern at Kirkdale. They were recognized at first sight by the keeper of a menagerie, to
whom they were shown, as resembling both in form and
appearance the feces of the spotted hyena; and, being
analyzed by Dr. Wollaston, were found to be composed
of the ingredients that might be expected in fecal matter
derived from bones-viz., phosphate of lime, carbonate
of lime, and a very small proportion of the triple phosphate of ammonia and magnesia. This discovery of the
coprolites of the hyena formed, perhaps, the strongest of
the links in that chain of evidence by which Dr. BuckFig. 70.        land proved that the cave at
Kirkdale, in Yorkshire, had
iii": ~~~~~been, during a long succession of years, inhabited as
a den by hyenas, and that
they dragged into its recesses the other animal bodies,
whose remains, splintered,
and bearing marks of teeth
of the hyena, were found
mixed indiscriminately with
their own.
SKULL AND TEETH OF THE MORSE.




TEETH OF THE PORCUPINE.              267
Before quitting the carnivorous order, the peculiar
development of the upper canines of the morse or walrus
deserve to be noticed. The staple food of this large modified seal is shell-fish, crustaceans, and sea-weed, which
are pounded to a pulp by its small obtuse molar teeth.
The canines (Fig. 70), c, exist only in the upper jaw,
where they are imbedded in deep and large prominent
sockets, whence they sweep down, slightly incurved,
forming large and long tusks, which serve as weapons of
attack and defence, and as instruments in aid of climbing
the floes and hummocks of ice, amongst which the walrus
passes its existence.
In the order of mammalia, called gnawers or rodents,
some of which, e. g. the rat, are mixed feeders, but most
of them herbivorous, the canine teeth are wanting in
both jaws, and the incisors, reduced to two in number,
are the seat of that excessive and uninterrupted growth,
which makes them allied to tusks.
These incisors (Fig. 71), i, are curved, the upper pair
Fig. 71.
SKULL AND TEETH OF A PORCUPINE.
describing a larger part of a smaller circle, the lower
ones a smaller part of a larger circle, the latter being the




268        TEETH OF THE PORCUPINE.
longest, and usually having their sockets extending from
the fore to the back part of the under jaw. The tooth
consists of a body of compact dentine, with a plate of
enamel laid upon its anterior or convex surface, and the
enamel commonly consists of two layers, of which the
anterior and external one is the densest. Thus the sub
stances of the incisor diminish in hardness from the front
to the back part of the tooth. The wear and tear from
the reciprocal action of the upper and lower incisors produce, accordingly, an oblique surface, sloping from a
sharp anterior margin formed by the denser enamel, like
that which, in a chisel, slopes from the sharp edge formed
by the plate of hard steel laid on the back of that tool,
whence these teeth have been called " chisel-teeth" (dentes
scalprarii). Their growth never ceases while the animal
lives, and the implanted part retains the form and size of
the exposed part, and ends behind in a widely open or
hollow base, which contains a long, conical, persistent
forming pulp. This law of unlimited growth is unconditional, and constant exercise and abrasion are required
to maintain the normal form and serviceable proportions
of the scalpriform teeth of the rodents. When, by accident, an opposing incisor is lost, or when, by the distorted
union of a broken jaw, the lower incisors no longer meet
the upper ones, as sometimes happens to a wounded hare
or rabbit, the incisors continue to grow until they project, like the tusks of the elephant, and the extremities,
in the poor animal's attempts to acquire food, also become
pointed like tusks. Following the curve prescribed to
their growth by the form  of their socket, their points
often return against some part of the head, are passed
through the skin, cause absorption of the bone, and perhaps again enter the mouth, rendering mastication im



TEETH OF THE RODENT MAMMALIA.    269
practicable, and causing death by starvation. In the
Museum of the College of Surgeons there is a lower jaw
of a beaver, in which the scalpriform incisor has, by unchecked growth, described a complete circle; the point
has pierced the masseter muscle, entered the back of the
mouth, and terminated close to the bottom of the socket
containing its own hollow root.
The difference in the diet of the rodent quadrupeds has
been alluded to; there is a corresponding difference in the
mode of implantation of their molar teeth. Those which
subsist on mixed food, and which, like the rats, betray a
tendency to carnivorous habits, or which subsist, like
squirrels, on the softer and more nutritious vegetable substances, as the kernels of nuts, suffer less rapid abrasion
of the grinding teeth; a less depth of crown is, therefore,
needed to perform the office of mastication during the
brief period of life allotted to these active little mammals;
and, as the economy of nature is manifested in the smallest
particulars as well as in her grandest operations, no more
dental substance is developed after the crown is formed
than is requisite for the firm fixation of the tooth in the
Jaw.
The rodents that exclusively subsist on vegetable substances, especially of the coarser and less nutritious kinds,
as herbage, foliage, and the bark and wood of trees, wear
away more rapidly the grinding surface of the molar
teeth; the crowns are, therefore, larger, and their growth
continues by a reproduction of the formative matrix at
their base in proportion as its calcified constituents, forming the working part of the tooth, are worn away. So
long as this reproductive force is active, the molar tooth
is implanted, like the incisor, by a long, undivided continuation of the crown. These rootless and perpetually
23*




270    TEETHl OF THE RODENT MAMMIALIA.
growing molars are always more or less curved, for they
derive from this form the same advantage as the incisors,
in the relief of the delicate tissues of the active vascular
matrix from the effects of the pressure which would otherwise have been transmitted more directly from the grinding surface; the capybara, and the Patagonian hare
(DoUichotis), afford good examples of this more complex
condition of the grinding teeth.
The variety in the pattern of the folds of enamel that
penetrate the substance of the tooth, and add to its triturating power, is almost endless; but the folds have always
a tendency to a transverse direction across the crown of
the tooth in the rodents. This direction relates to the
shape of the joint of the lower jaw, which almost restricts
it to horizontal movements to and fro, during the act of
mastication. In the true hoofed herbivorous animals, in
which the joint of the lower jaw allows a free rotatory
movement, the folds of enamel take other forms and
directions, with modifications, constant in each genus, and
characteristic of such.
The horse is here selected as an example of such herbivorous dentition (Fig. 72). The grinding teeth are six
in number, on each side of both upper and lower jaws,
with thick square crowns of great length, and deeply implanted in the sockets, those of the upper jaw being
slightly curved. When the summits or exposed ends of
these teeth begin to be worn down by mastication, the
interblended enamel, dentine, and cement show the pattern figured in Cut 72; it is penetrated from within by a
valley, entering obliquely from behind forwards, and
dividing into or crossed by the two crescentic valleys,
which soon become insulated. There is a large lobe at
the end of the valley. The outer surface of the crown is




TEETII  OF THE HORSE.               271
impressed by two deep longitudinal channels.. In the lower
jaw the teeth are narrower transversely than in the upper
jaw, and are divided externally into two convex lobes, by
a median longitudinal fissure; internally they present
three principal unequal convex ridges, and an anterior
and posterior narrower ridge. All the valleys, fissures,
Fig. 72.
-tHF~s  %t~L           ~         ", _3 AkZ
GRINDING SURFACES OF THE UPPER AND LOWER MOLARS OF A HORSE.
and folds in both upper and lower grinders are lined by
enamel, which also coats the whole exterior surface of the
crown. Of the series of six teeth in each jaw, the first
three, p 2,-3, 4, are premolars, the rest, m 1, 2, 3, are true
molars.
The canines are small in the horse, and are rudimental
in the mare; the unworn crown is remarkable for the
folding in of the anterior and posterior margins of enamel.
The upper canine is situated in the middle of the long
interspace between the incisors and molars; the lower
canine is close to the outer incisor, but is distinguished by
its more pointed form. The incisors are six in number
in both jaws; they are arranged close together in a curve,




272  DEVELOPMENT OF TEETH IN THE HORSE.
at the end of the jaw; the crown is broad, and the contour
of the biting surface, before it is much worn, approaches
an ellipse. The incisors of the horse are distinguished
from those of ruminants by their greater length and curvature, and from those of all other animals by the fold of
enamel (Fig. 55), a, which penetrates the crown from its
flat summit, like the inverted finger of a glove. When
the tooth begins to be worn, the fold becomes an island
of enamel, inclosing a cavity partly filled by cement, and
partly by the substances of the food, and is called the
"mark."  In aged horses, the incisors are worn down
below the extent of the fold, and the "mark" disappears.
This cavity is usually obliterated in the first or mid incisors at the sixth year, in the second incisors at the
seventh year, and in the third or outer incisors at the
eighth year, in the lower jaw. The mark remains somewhat longer in the incisors of the upper jaw.
The following is the average course of development
and succession of the teeth in the horse (Equus caballus):
The summits of the first functional deciduous molar, d, 2,
"first grinder" of veterinary authors, are usually apparent at birth; the succeeding grinder, d 3, sometimes
arises a day or two later, sometimes together with the
first. Their appearance is speedily followed by that of
the first deciduous incisor —"centre nipper" of veterinarians-which usually cuts the gum between the third and
sixth days. The second deciduous incisor appears between the twentieth and fortieth days, and about this
time the rudimental grinder, p 1, comes into place, and
the last deciduous molar, d 4, begins to cut the gum;
about the sixth month the inferior lateral, or third incisors, with the deciduous canine, make their appearance.
The minute canine is shed about the time that the con



TEETH OF THE ELEPHANT.              273
tiguous incisor is in place, and is not retained beyond
the first year. The upper deciduous canine is shed in
the course of the second year. The first true molar, m 1,
appears between the eleventh and thirteenth months.
The second molar follows before the twentieth month.
The first functional premolar, p 2, displaces the deciduous molar, d 2, at from two years to two years
and a half old. The first permanent incisor protrudes
from the gum at between two years and a half and three
years. At the same period, the penultimate premolar, p
3, pushes out the penultimate milk molar, d 3, and
the penultimate true molar comes into place. The last
premolar displaces the last deciduous molar at between
three years and a half and four years; the appearance
above the gum of the last true molar, m 3, is usually
somewhat earlier. The second incisor pushes out its
deciduous predecessor about the same period. The permanent canine, or "tusk," next follows; its appearance
indicates the age of four years, but it sometimes comes
earlier. The third, or outer incisor, pushes out the deciduous incisor about the fifth year, but is seldom in full
place before the horse is five and a half years old. Upon
the rising of the third permanent incisor, or "corner
nipper" of the veterinarians, the "colt" becomes a "horse,"
and the "filly," a "mare," in the language of the horsedealers. After the disappearance of the "mark" in the
incisors, at the eighth or ninth year the horse becomes
"aged."
The most complex condition of teeth adapted to a
vegetable diet is that presented by the elephant. The
dentition of the genus Elephas includes two long tusks
(Fig. 73), one in each of the intermaxillary bones, and large
and complex molars (ib.), rn 3, 4, and 5, in both jaws; of




274         TEETH OF THE ELEPHANT.
the latter there is never more than one wholly, or two
partially, in place and use on each side at any given time,
Fig. 73.
SECTION OF SKULL AND TEETH OF ELEPHANT.
for the series is continually in progress of formation and
destruction, of shedding and replacement; and all the
grinders succeed one another, like true molars, horizontally, from behind forward.
The total number of teeth developed in the elephant
appears to be i2  2m77 —- 32, the two large permanent
0-0  7-7
incisors being preceded by two small deciduous ones, and
the number of molar teeth which follow one another on
each side of both jaws being seven, or at least six, of




TEETH OF THE ELEPHANT.                275
which the last three may, by analogy, be regarded as
answering to the true molars of other pachyderms.
The incisors not only surpass other teeth in size, as
belonging to a quadruped so enormous, but they -are the
largest of all teeth in proportion to the size of the body;
representing, in a natural state, those monstrous tusks of
the rodents, which are the result of accidental suppression of the wearing force of the opposite teeth.
The tusks of the elephant consist chiefly of that modification of dentine that is called " ivory," and which shows,
on transverse fractures or sections, strie proceeding in
the arc of a circle from the centre to the circumference,
in opposite directions, and forming by their decussations
curvilinear lozenges. This character is peculiar to the
tusks of the proboscydian pachyderms.
In the Indian elephant, the tusks are always short and
straight in the female, and less deeply implanted than in
the male; she thus retaining, as usual, more of the characters of the immature state. In the male, they have
been known to acquire a length of nine feet, with a basal
diameter of eight inches, and to weigh one hundred and
fifty pounds; but these dimensions-are rare in the Asiatic
species.
A mammoth's tusk has been dredged up off Dungeness
which measured eleven feet in length.' In several of
the instances of mammoth's tusks from British strata, the
ivory has been so little altered as to be fit for the purposes of manufacture; and the tusks of the mammoth,
which are still better preserved in the frozen drifts of
Siberia, have long been collected in great numbers as
articles of commerce. In the account of the mammoth's
I Owen's "History of British Fossil Mamlmalia," 8vo. 1844, p. 244.




276        TEETH OF THE ELEPIIANT.
bones and teeth of Siberia, published in the Philosophical
Transactions for 1737, 1No. 446, tusks are cited which
weighed two hundred pounds each, and "are used as
ivory to make combs, boxes, and such other things, being
but little more brittle, and easily turning yellow by weather and heat."  From that time to the present there has
been no intermission in the supply of ivory, furnished by
the tusks of the extinct elephants of a former world.
The musket-balls and other foreign bodies which are
occasionally found in ivory, are immediately surrounded
by osteo-dentine in greater or less quantity. It has often
been a matter of wonder how such bodies should become
completely imbedded in the substance of the tusk, sometimes without any visible aperture, or how leaden bullets
may have become lodged in the solid centre of a very
large tusk without having been flattened. The explanation is as follows: a musket-ball, aimed at the head of
an elephant, may penetrate the thin bony socket and the
thinner ivory parietes of the wide conical pulp-cavity
occupying the inserted base of the tusk; if the projectile
force be there spent, the ball will gravitate to the opposite
and lower side of the pulp-cavity, as indicated in Fig. 73.
The presence of the foreign body exciting inflammation
of the pulp, an irregular course of calcification ensues,
which results in the deposition around the ball of a certain thickness of osteo-dentine. The pulp then resuming
its healthy state and functions, coats the surface of the
osteo-dentine inclosing the ball, together with the rest of
the conical cavity into which that mass projects, with
layers of normal ivory.
The portions of the cement-forming capsule suriounding the base of the tusk, and the part of the pulp, which
were perforated by the ball in its passage, are soon re



TEETH OF TIlE ELEPHANT.            277
placed by the active reparative power of these highly
vascular bodies. The hole formed by the ball in the base
of the tusk is then more or less completely filled up by
a thick coat of cement from without, and of osteo-dentine
from within.
By the continued progress of growth, the ball so inclosed is carried forwards, in the course indicated by the
arrow in Fig. 73, to the middle of the solidified exserted
part of the tusk. Should the ball have penetrated the
base of the tusk of a young elephant, it may be carried
forwards by the uninterrupted growth and wear of the
tusk, until that base has become the apex, and be finally
exposed and discharged by the continual abrasion to
which the apex of the tusk is subjected.
I had the tusk and pulp of the great elephant at the
Zoological Gardens longitudinally divided, soon after the
death of that animal in the summer of 1847. Although
the pulp could be easily detached from the inner surface
of the pulp-cavity, it was not without a certain resistance;
and when the edges of the coadapted pulp and tooth were
examined by a strong lens, the filamentary processes from
the outer surface of the pulp could be seen stretching as
they were withdrawn from the dentinal tubes before they
broke. They are so minute that, to the naked eye, the
detached surface of the pulp seems to be entire, and Cuvier was thus deceived in concluding that there was no
organic connection between the pulp and the ivory.
The molar teeth of the elephant are remarkable for
their great size, even in relation to the bulk of the animal, and for the extreme complexity of their structure.
The crown, of which a great proportion is buried in the
socket, and very little more than the grinding surface
appears above the gum, is deeply divided into a number
24




278         TEETH OF THE ELEPHANT.
of transverse perpendicular plates, consisting each of a
body of dentine, coated by a layer of enamel, e, and this
again by the less dense bone-like substance, c, which fills
the interspaces of the enamelled plates, and here more
especially merits the name of "cement," since it binds
together the several divisions of the crown before they
are fully formed and united by the confluence of their
bases into a common body of dentine. As the growth
of each plate begins at the summit, they remain detached,
and like so many separate teeth or denticules, until their
base is completed, when it becomes blended with the bases
of contiguous plates to form the common body of the
crown of the complex tooth, from which the roots are
next developed.
Fig. 74.
C! 
dd
African.              Asiatic.         Elephas priinfgenius.
MOLAR TEETH OF ELEPHANTS AND THE SIBERIAN IAMM3IOTH.




TEETH OF THE ELEPHANT.              279
The plates of the molar teeth of the Siberian mammoth
(Elephas primigenius), (Fig. 74), are thinner in proportion
to their breadth, and are generally a little expanded at
the middle; and they are more numerous in proportion
to the size of the crown than in the existing species of
Asiatic elephantj(ib.). In the African elephant (ib.), on
the other hand, the lamellar divisions of the crown are
fewer and thicker, and they expand more uniformly from
the margins to the centre, yielding a lozenge-form when
cut or worn transversely, as in mastication.
The formation of each grinder begins with the summits
of the anterior plate, and the rest are completed in succession; the tooth is gradually advanced in position as its
growth proceeds; and in the existing Indian elephant the
anterior plates are brought into use before the posterior
ones are formed. When the complex molar cuts the gum,
the cement is first rubbed off the digital summits; then
their enamel cap is worn away, and the central dentine
comes into play with a prominent enamel ring; the digital processes are next ground down to their common
uniting base, and a transverse tract of dentine, with its
wavy border of enamel, is exposed; finally, the transverse plates themselves are abraded to their common
base of dentine, and a smooth and polished tract of that
substance is produced. From this basis the roots of the
molar are developed, and increase in length to keep the
worn crown on the grinding level, until the reproductive
force is exhausted. When the whole extent of a grinder
has successively come into play, its last part is reduced to
a long fang, supporting a smooth and polished field of
dentine, with, perhaps, a few remnants of the bottom of
the enamel folds at its hinder part. When the complex




280         TEETH OF THE ELEPHANT.
molar has been thus worn down to a uniform surface, it
becomes useless as an instrument for grinding the coarse
vegetable substances on which the elephant subsists; it is
attacked by the absorbent action, and the wasted portion
of the molar is finally shed.
The grinding-teeth of the elephant progressively increase
in size, and in the number of lamellar divisions, from the
first to the last; they succeed each other from behind
forwards, moving not in a right line, but in the arc of a
circle, shown by the curved line in Fig. 73. The position
of the growing tooth in the closed alveolus, m, 5, is almost
at right angles with that in use, the grinding surface being
at first directed backwards in the upper jaw, and forwards
in the lower jaw, and brought by the revolving course
into a horizontal line in both jaws, so that they oppose
each other when developed for use. The imaginary pivot
on which the grinders revolve is next their root in the
upper jaw, and is next the grinding surface in the lower
jaw; in both, towards the frontal surface of the skull.
Viewing both upper and lower molars as one complex
whole, subject to the same revolving movement, the section dividing such whole into upper and lower portions
runs parallel to the curve described by the movement,
the upper being the central portion, or that nearest the
pivot; the lower, the peripheral portion. The grinding
surface of the upper molars is consequently convex from
behind forwards, and that of the lower molars concave;
the upper molars are always broader than the lower ones.
The bony plate forming the sockets of the growing
teeth is more than usually distinct from the body of the
maxillary, and participates in this revolving course, advancing forwards with the teeth.




SUCCESSION OF THE ELEPHANT'S GRINDERS. 281
SUCCESSION.-As the rate of increase, both of size and
in the number of the component plates of the grinding
tooth, is nearly identical in both jaws, it will suffice to
briefly describe the teeth and the periods at which they
successively appear in the lower jaw of the Asiatic elephant.
The first molar, which cuts the gum in the course of
the second week after birth, has a sub-compressed crown,
nine lines in antero-posterior diameter, divided by three
transverse clefts into four plates, the third being the
broadest, and the tooth here measuring six lines across;
the base slightly contracts, and forms a neck as long as
the enamelled crown, but of less breadth, and this divides
into an anterior and posterior, long, sub-cylindrical, diverging, but mutually incurved fangs; the total length
of this tooth is one inch and a half. The corresponding
upper molar cuts the gum a little earlier than the lower
one: the neck of this tooth is shorter, and the two fangs
are shorter, larger, and more compressed than those of
the lower first molar. The first molar of the elephant is
the homologue of the probably deciduous molar (Fig.
75), d2, in other ungulates; it is not a mere miniature
of the great molars of the mature animal, but retains,
agreeably with the period of life at which it is developed,
a character much more nearly approaching that of the
ordinary pachydermal molar, manifesting the adherence
to the more general type by the minor complexity of the
crown, and by the form and relative size of the fangs.
In the transverse divisions of the crown we perceive the
affinity to the tapiroid type, the different links connecting
which with the typical elephants are supplied by the extinct lophiodons, dinotheriums, and mastodons.  The
24*




282  SUCCESSION OF THE ELEPHANT'S GRINDERS.
subdivision of the summits of the primary plates recalls
the character of the molars, especially the smaller ones,
of the phacochere in the hog tribe. As the elephant advances in age, the molars rapidly acquire their more special and complex character.
The first molars are completely in place and in full
use at three months, and are shed when the elephant is
about two years old.
The sudden increase and rapid development of the
second molar may account for the non existence of any
vertical successor, or " premolar," to the former tooth, in
the elephant. The eight or nine plates of the crown are
formed in the closed alveolus, behind the first molar by
the time this cuts the gum, and they are united with the
body of the tooth, and most of them in use, when the
first molar is shed. The average length of the second
molar is two inches and a half, ranging from two inches
to two inches and nine lines. The greatest breadth,
which is behind the middle of the tooth, is from one
inch to one inch three lines. There are two roots; the
cavity of the small anterior one expands in the crown,
and is continued into that of the three anterior plates.
The thicker root supports the rest of the tooth. The
second molar is worn out and shed before the beginning
of the sixth year.
The third molar has the crown divided into from eleven
to thirteen plates; it averages four inches in length, and
two inches in breadth, and has a small anterior, and a
very large posterior root; it begins to appear above the
gum about the end of the second year, is in its most
complete state and extensive use during the fifth year,
and is worn out and shed in the ninth year. The last




SUCCESSION OF THE ELEPHANT'S GRINDERS. 283
remnant of the third molar is shown at m 3 (Fig. 73). It
is probable that the three preceding teeth are analogous
to the deciduous molars, d2, d 3, and d 4, in the hog
(Fig. 75).
The fourth molar presents a marked superiority of size
over the third, and a somewhat different form; the anterior angle is more obliquely abraded, giving a pentagonal
figure to the tooth in the upper jaw (Fig. 73), m 4. The
number of plates in the crown of this tooth is fifteen or
sixteen, its length between seven and eight inches, its
breadth three inches. It has an anterior simple and
slender root supporting the first three plates, a second of
larger size and bifid, supporting the four next plates, and
a large contracting base for the remainder. The forepart of the grinding surface of this tooth begins to protrude through the gum at the sixth year; the tooth is
worn away, and its last remnant shed, about the twentieth
or twenty-fifth year. It may be iregarded as the homologue of the first true molar of ordinary pachyderms
(Fig. 75), m 1.
The fifth molar, with a crown of from seventeen to
twenty plates, measures between nine and ten inches in
length, and about three inches and a half in breadth.
The second root is more distinctly separated from the
first simple root than from the large mass behind. It
begins to appear above the gum about the twentieth
year; its duration has not been ascertained by observation, but it probably is not shed before the sixtieth year.
The sixth molar is the last, and has from twenty-two
to twenty-seven plates; its length, or antero-posterior
extent, following the curvature, is from twelve to fifteen
inches; the breadth of the grinding surface rarely ex



284  DEVELOPMENT OF ELEPHANT'S GRINDERS.
ceeds three inches and a half. One may reasonably conjecture that the sixth molar of the Indian elephant, if it
make its appearance about the fiftieth year, would, from
its superior depth and length, continue to do the work of
mastication until the pondrous pachyderm had passed
the century of its existence.
DEVELOPMENT.- The long-mistaken phenomena of the
formation of the dental substances will be here described
as they have been observed in the large teeth of the elephant; if the description be comprehended in regard to
these, the most complex members of the dental system,
the true theory of dental development will be readily
understood in regard to all the various forms and gradations of teeth. The matrix, or formative organ of the
tusk, consists of a large conical pulp, which is renewed
quicker than it is converted, and thus is not only preserved, but grows, up to a certain period of the animal's
life; it is lodged in the cavity at the base of the tusk;
this base is surrounded by the remains of the capsule, a
soft, vascular membrane of moderate thickness, which is
confluent with the border of the base of the pulp, where
it receives its principal vessels.
Each molar of the elephant is formed in the interior
of a membranous sac-the capsule, the form of which
partakes of that of the future tooth, being cubical in the
first molar, oblong in the last, and rhomboidal in most of
the intermediate teeth; but always decreasing in vertical
extent towards its posterior end, and closed at all points,
save where it is penetrated by vessels and nerves. It is
lodged in an osseous cavity of the same form as itself,
and usually in part suspended freely in the maxillary
bone, the bony case being destined to form part of the




DEVELOPMENT OF ELEPHANT'S GRINDERS. 285
socket of the tooth. The exterior of the membranous
capsule is simple and vascular, as shown at m 5, Fig. 73;
its internal surface gives attachment to numerous folds
or processes, as in most other ungulate animals.
The dentinal pulp rises from the bottom of the capsule,
or that part which lines the deepest part of the alveolus,
in the form of transverse parallel plates extending towards that part of the capsule ready to escape from the
socket. These plates adhere only to the bottom of the
capsule; their opposite extremity is free from all adhesion. This summit is thinner than the base; it might be
termed the edge of the plate; but it is notched, or divided
into many digital processes. The tissue of these digitated
plates is identical with that of the dentinal pulp of simple
Mammalian teeth; it becomes also highly vascular at the
parts where the formation of the dentine is in active
progress.
Processes of the capsule descend from its summit into
the interspaces of the dentinal pulp-plates, and consequently resemble them in form; but they adhere not only
by their base to the surface of the capsule next the mouth,
but also by their lateral margins to the sides of the capsule, and thus resemble partition-walls, confining each
plate of the dentinal pulp to its proper chamber; the
margin of the partition opposite its attached base is free
in the interspace of the origins of the dentinal pulpplates.
The enamel organ, which Cuvier appears to have re-,
cognized under the name of the internal layer of the capsule, is distinguishable by its light blue sub-transparent
color and usual microscopic texture, adhering to the free
surface of the partitions formed by the true inner layer




286 DEVELOPMENT OF ELEPHANT'S GRINDERS.
of the capsule. Although the enamel-pulp be in close
contact with the dentinal pulp prior to the commencement of the formation of the tooth, one may readily conceive a vacuity between them, which is continued uninterruptedly, in many foldings, between all the gelatinous
plates of the dentinal pulp, and the partitions formed by
the combined enamel-pulp and the folds of the capsule.
According to the excretion view, this delicate apparatus
must have been immediately subjected to the violence of
being compressed in the unyielding bony box, by the deposition of the dense matters of the tooth in the hypothetical vacuity between the enamel and dentinal pulps;
a process of absorption must have been conceived to be
set on foot immediately that the altered condition of the
gelatinous secreting organs took place; and, according to
Cuvier's hypothesis, the secreting function must be supposed to have proceeded, without any irregularity or interruption, while the process of absorption was superinduced in the same part to relieve it from the effects of
pressure produced by its own secretion.
The formation of the dentine commences immediately
beneath the membrana propria of the pulp; a part which
Cuvier distinctly recognized, and which he accurately
traced as preserving its relative situation between the
dentine and enamel throughout the whole formation of
the dentine, and discernible in the completed tooth " as a
very fine grayish line, which separates the enamel from
the internal substance," or dentine.
The calcification and conversion of the cells of the
dentinal pulp commence as usual at the peripheral parts
of the lamelliform processes furthest from the attached
base. It may readily be conceived, therefore, that, at the




I'EVELOPMENT OF ELEPHANT'S GRINDERS. 287
commencement, there is formed a little cap upon each of
the processes into which the edges of the pulp-plates are
divided. As the centripetal calcification proceeds, the
caps are converted into horn-shaped cones. When it has
reached the bottom of the notches of the edge of the pulpplate, all the cones become united together into a single
transverse plate; and, the process of conversion, having
reached the base of the pulp-plate, these plates coalesce
to form a common base to the crown of the tooth, which
would then present the same eminences and notches that
characterized the gelatinous pulp, if, during the period of
conversion, other substances had not been formed upon
the surface and in the interspaces of the pulp-plates.
Coincident, however, with the formation of the dentine,
is the deposition of the hardening salts of the enamel in
the extremely slender prismatic cells, which are for the
most part vertical to the plane of the inner surface of the
folds of the capsule to which they are attached. The
true inner part of the capsule forms those thick transverse
folds or partitions which support the enamel organ, and
with it fill the interspaces of the dentinal pulps. With
regard to the formation of the cement, Cuvier, after citing
the opinion of Tenon-that it was the result of ossification of the internal layer of the capsule, and that of
Blake-that it was a deposition from the opposite surface
of the capsule to that which had deposited the enamel,
states his own conviction to be that the cement is produced by the same layer and by the same surface as that
which has produced the enamel. The proof alleged is,
that so long as any space remains between the cement
and the external capsule, that space is found to contain a
soft internal layer of the capsule with m free surface next
the cement. The phenomena could not, in fact, be other



288  DEVELOPMENT OF ELEPHANT'S GRINDERS.
wise explained according to the "excretion theory" of
dental development. To the obvious objection that the
same part is made, in this explanation, to secrete two
different products, Cuvier replies, that it undergoes a
change' of tissue: " Vhilst it yielded enamel only, it was
thin and transparent; to give cement, it becomes thick,
spongy, and of a reddish color." The external characters
of the enamel-organ and cement-forming capsule are correctly defined; only, the one, instead of being converted
into the other, is in fact changed into its supposed transudation; the enamel fibres being formed, and properly disposed in the direction in which their chief strength is to
lie, by the assimilative properties of the prearranged
elongated, prismatic, non-nucleated cells, which take from
the surrounding plasma the required salts, and compact
them in their interior.
Whilst this process is on foot, and before the enamel
fibres are firm in their position, the capsule begins to
undergo that change which results in the formation of the
thick cement; the calcifying process commences from
several points, and proceeds centrifugally, radiating therefrom, and differing from the ossification of bone chiefly
in the number of these centres, which, though close to the
new-formed enamel, are in the substance of the inner
vascular surface of the capsular folds. The cells arrange
themselves in concentric layers around the vessels, and
act like those of the enamel pulp in receiving into their
interior the bone-salts in a clear and compact state. During this process they become confluent with each other,
their primitive distinctness being indicated only by their
persistent granular nuclei, which now form the radiated
Purkingian capsules. The interspaces of the concentric
series of confluent cells become filled with the calcareous




DEVELOPMENT OF ELEPHIANT'S GRINDERS. 289
salts in a rather more opaque state; and the conversion of
the capsule into cement goes on, according to the processes more particularly described in the Introduction to
my Odontograjphy, until a continuous stratum is formed
in close connection with the layer of enamel.
Calcification extending from the numerous centres, the
different portions coalesce, and progressively add to the
thickness of the cement, until all the interspaces of the
coronal plates and the whole exterior of the crown are
covered with the bone-like substance. The enamel-pulp
ceases to be developed at the base of the crown, but the
capsule continues to be formed _paHr, passu with the partial
formation of the pulp, as this continues, progressively
contracting, from the base of the crown, to form, by its
calcification, the roots. The calcification of the capsule
going on at the same time, a layer of cement is formed
in immediate connection with the dentine. The circumscribed spaces at the bottom of the socket to which the
capsule and dentinal pulp adhere, where they receive
their vessels and nerves, and which are the seat of the
progressive formation of these respective moulds of the
two dental tissues, become gradually contracted, and subdivided by the further localization of the reproductive
forces to particular spots, whence the subdivision of the
base into roots. The surrounding bone undergoes corresponding modifications, growing and filling up the interspaces left by the dividing and contracting points of
attachment of the residuary matrix. All is subordinated
to one harmonious law of growth by vascular action and
cell-formation, and of molecular decrement by absorption.
Mechanical squeezing, or drawing out, has no share in
these changes of the pulp or capsule; pressure at most
25




290  DEVELOPMENT OF ELEPHANT'S GRINDERS.
exercises only a gentle stimulus to the vital processes.
Cuvier believed that there were places where the dentinal
pulp and the capsule were separate from each other. I
have, never found such, except where the enamel-pulp
was interposed between them in the crown of the tooth,
or where both pulp and capsule adhered to the periosteum
of the socket, below the crown. Cuvier affirms that the
number of fangs of an elephant's molar depends upon
the number of points at which the base of the gelatinous
(dentinal) pulp is attached to the bottom of the capsule;
and that the interspaces of these attachments constitute
the under part of the crown or body of the tooth, the
attachments themselves forming the first beginnings of
the fangs. True to his hypothesis of the formation of the
dental tissues by excretion, he says that the elongation
of the fangs is produced by two circumstances; first, the
progressive elongation of the layers of osseous substance
(dentine) which force the tooth to rise and emerge from
its socket; secondly, the thickening of the body of the
tooth by the addition of successive layers to its inner surface, which, filling up the interior cavity, leaves scarcely
room for the gelatinous pulp, and forces it down into the
interior of the roots.
This pulling up of the fang on the one hand, and squeezing down the pulp on the other, are forces too gross and
mechanical to be admitted in actual physiology to explain
the growth of the root of a tooth or of any other organized
product; such modes of explanation were, however, inevitable in adopting the "excretion theory" of dental
development.
There are few examples of organs that manifest a more
striking adaptation of a highly complex and beautiful
structure to the exigences of the animal endowed with it,




DEVELOPMENT OF ELEPHANT'S GRINDERS.  291
than the grinding teeth of the elephant. We perceive, for
example, that the jaw is not incumbered with the whole
weight of the massive tooth at once, but that it is formed
by degrees as it is required; the division of the crown
into a number of successive plates, and the subdivision of
these into cylindrical processes, presenting the conditions
most favorable to progressive formation. But a more
important advantage is gained by this subdivision of the
tooth; each part is formed like a perfect simple tooth,
having a body of dentine, a coat of enamel, and an outer
investment of cement. A single digital process may be
compared to the simple canine of a carnivore; a transverse
row of these, therefore, when the work of mastication has
commenced, presents by virtue of the different densities
of their constituent substances, a series of cylindrical
ridges of enamel, with as many depressions of dentine, and
deeper external valleys of cement; the more advanced
and more abraded part of the crown is traversed by the
transverse ridges of the enamel inclosing the depressed
surface of the dentine, and separated by the deeper channels of cement; the forepart of the tooth exhibits its least
efficient condition for mastication, the inequalities of the
grinding surface being reduced, in proportion as the
enamel and cement have been worn away. This part of
the tooth is, however, still fitted for the first coarse crushing of the branches of a tree; the transverse enamel
ridges of the succeeding part of the tooth divide it into
smaller fragments, and the posterior islands and tubercles
of enamel pound it to the pulp fit for deglutition.
The structure and progressive development of the
tooth not only give to the elephant's grinder the advantage
of the uneven surface which adapts the millstone for its
office, but, at the same time, secure the constant presence




292       TEETH OF THE MEGATHERIUM.
of the most efficient arrangement for the finer comminution of the food, at the part of the mouth which is nearest
the fauces.
In the tusks of the 1fastodon giganteus, the outer laver
of cement is relatively thicker than in the tusks of the
mammoth, or in those of the Indian elephant. The general character of the microscopic structure of the ivory
of the masto(lon's tusk is the same as that of the elephant.
By the minuteness and close arrangement of the dentinal tubes, and especially by their strongly undulating
secondary curves, a tougher and more elastic tissue is
produced than results from their disposition in ordinary
dentine; and the modification which distinguishes " ivory"
is doubtless essential to the due degree of coherence of so
large a mass as the elephant's tusk, projecting so far from
the supporting socket; and to be frequently applied in
dealing hard blows and thrusts.
TEETII OF TIIE  MEGATIIERIUM.
The megatherium (Gr. megas, great; therion, beast), so
called from  its colossal size-being as large as the
elephant, and even surpassing that hugest of existing
quadrupeds in some of its proportions-was once an inhabitant, and apparently in some numbers, of the American continent, especially its southern division, and subsisted on a similar kind of food to the elephants, viz: the
smaller branches and leaves of trees; but all the genera
and species of megatheroid beasts are now extinct.
Nevertheless, from the fossil remains of the megatherium
the anatomist is able unerringly to deduce the nature of




TEETH OF THE MIEGATHERIUM,            293
its food and many of its peculiar habits; and also to bring
to light a system of dentition, designed, like that of the
elephants, for the service of crushing and masticating a
coarse vegetable diet throughout a long-protracted individual existence; and yet, by a modification of the formative processes and economy of the teeth, quite different
from those that have been adopted for the same ends in
the elephant tribe.
In these, as has been shown, the supply of a masticating apparatus, to serve the requirements of a gigantic
animal during one or perhaps two centuries of existence,
was provided by a succession of dicferet molar teeth presenting the due complexity of structure. In the megatherium, the same end was obtained by a perpetual growth
of the same complex molar teeth-the different dental
substances being formed at and added to the base of the
tooth, in proportion as they were ground down at the
exposed summit.
The true number of teeth was determined by a removal
of the mineral substances adhering to the surface of a
portion of a fossil skull of a megatherium, brought by
Mr. Charles Darwin, from South America (Fossil Mamin
malia of the UVoyage of the Beagloe," 4to. 1840, p, 102),
The animal has not, as in the elephlant, any tusks; its
teeth are molars or grinders exclusively; they are five in
number on each side of the upper jaw, and four on each
side of the lower jaw-eighteen in all. All these teeth
are remarkable for their great length in proportion to
their breadth or thickness,.being from eight to ten. inches
in length, and between two and three inches only in
breadth. They are very deeply implanted in the jaw,
and the lower jaw has a quite peculiar form, in order to
25



294  DENTAL SYSTEM OF THE MEGATIIERIUM.
acquire the requisite room for the lodgement of the lower
teeth and their "matrices," or formative organs.
The next peculiarity to be noticed in these remarkable
teeth is the great length of the conical cavity at their
base, for lodging the part of the matrix called the " pulp;"
the apex of the pulp-cavity rising as far as the part of the
tooth where it emerges from the socket. A transverse
fissure is continued from this apex to the middle concavity
of the grinding surface of the tooth, which is thus divided
into two halves. Each of these halves consists of three
distinct substances-a central column of "vaso-dentine,"
a peripheral and nearly equally thick layer of " cement,"
and an intermediate thinner stratum  of true or "hard
dentine." This latter has been described as being enamel;
but it is only analogous to that differently constituted
and harder substance in the compound teeth of the elephant, in regard to its relative situation, and its degree of
density to the other constituents of the tooth of the megatherium.
No species of the order called "Bruta," or "Edentata,"
to which the extinct megatherium belongs, has true enamel entering into the composition of its teeth; but the
modifications of structure which the teeth present in the
different genera of this order are considerable, and their
complexity is not less that that of the enamelled teeth of
the herbivorous, ruminant, and other hoofed animals, in
consequence of the introduction of a dental substance-the
" vaso-dentine"-into their composition, analogous in structure to that of the teeth of the Myliobates and other cartilaginous fishes. The cement of the megatherium's tooth
differs from the vaso-dentine in the larger size and wider
interspaces of its medullary canals, and by the presence
of radiated bone-cells in their interspaces; but they are




DENTAL SYSTEMI OF THE MEGATHERIUMI.  295
brought into organic communication with each other, not
only by means of the tubes of coarse dentine, but by
occasional continuity of the vascular canals across that
substance. The tooth of the megatherium thus offers an
unequivocal example of a course of nutriment from the
dentine to the cement, and reciprocally; so that the main
substance, or body of the tooth, can obtain the requisite
supply for its languid vitality from the vessels of the capsule as well as from those of the pulp.
The conical cavity at the base of the tooth attests the
large size, and demonstrates the form of the persistent
pulp in the living megatherium; the diameter of its base
is equal to the part of the tooth which is formed by the
combined dentine and vaso-dentine. From the gradual
thinning off and final disappearance of those substances
as they reach the base of the tooth, it may be inferred
that both were formed at the expense of the pulp. The
fine dentinal tubes must have been established and calcified in the peripheral layer of the pulp, which layer
must have been wholly so converted into the dentine;
but as the deposition of the hardening salts proceeded
in the rest of the pulp, certain tracts of that soft and
vascular substance were left uncalcified, to form the medullary or vascular canals which characterize the vasodentine.  The space between the inserted base of the
tooth and the walls of the socket indicates the thickness of the dental capsule, by the ossification of which the
exterior layer of cement was formed; anid this modification of the tooth-forming organ in the megatherium permitted the progressive addition of cement, as the persistence of the compound pulp occasioned the uninterrupted
and continuous formation of the harder dentine, which is
analogous to the enamel in the elephant's grinder.




296  DENTAL SYSTEM OF THE MEGATHERIUM.
In all essential characters the teeth of the megatherium
repeat, on a magnified scale, the dental peculiarities of the
sloth;- and since, from a similarity of the form, number,
kinds, and structure of teeth, a similarity of food is to be
inferred, it may be concluded that the leaves and soft
succulent sprouts of trees formed the staple diet of the
megatherium, and of the cognate and contemporary megalonyx and mylodon, as of the existing sloths. The
enormous claws of those great extinct sloth-like quadrupeds, to judge by the fossorial (digging and scratching)
character of the powerful mechanism of the limbs that
worked them, were employed, not, as in the sloths, to
carry the animal to its food, but to bring the food within
the reach of the animal, by uprooting the trees on which
it grew.
In the remains of the megatherium, we have evidence
of the framework of a quadruped equal to the task of undermining and tearing down the largest trees in a tropical forest. In the latter operation, it is obvious that
the immediate application of the anterior extremities to
the trunk of the tree would demand a corresponding
fulcrum to be effectual; and it is the necessity for an adequate basis of support and resistance to such an application of the fore-extremities which gives the explanation
of the seemingly anomalous development of the pelvis,
tail, and hinder extremities of the megatherium and its
extinct allies. No wonder, therefore, that their type of
structure should be so peculiar; for, where shall we now
find quadrupeds equal, like them, to the habitual task of
uprooting trees for food.




TEETH OF THE EXTINCT ANOPLOTHERIUM. 297
TEE TII  OF THE ANOPLOTHERIUM.
Of the extinct quadrupeds with hoofs, and which were
consequently herbivorous, the species restored by Cuvier
from fossil remains discovered in the quarries at Montmartre, near Paris, was one of the most ancient. The
great comparative anatomist called it anoplotlherium, from
the Greek words signifying " weaponless," because it had
neither horns nor tusks. It was, however, characterized
by the most complete system of dentition; for it not only
possessed incisors and canines in both jaws, but these
were so equably developed that they formed one unbroken series with the premolars and molars, which character is now found only in the human species.
The dental formula of the genus Anoplolheriurn is ex-.3-3  1-1  4-4   3-3
pressed by:        c 1_ 1,p4, m _     = 44, signify3  3'  1   4  4 3  3
ing that it had, on each side of both upper and lower
jaws, three incisors, one canine, four premolars, and three
true molars; in all, forty-four teeth.
Those teeth which are transitorily manifested in the
embryo state of some ruminants, as the upper incisors
and canines and the anterior premolars, p 1, were in the
ancient anoplothere retained and raised to a proportional
equality of size and function with the rest of the teeth.
The true molars had a broad grinding surface, with enamel-covered crescentic lobes, remotely resembling those
of the existing ruminants. In some of the smaller species
of anoplotherium, the ruminant type of grinding surface
was more closely adhered to, and the fossil lower jaws of
such species, as e.g. of the Dichobune cervinum, have been




298           TEETH OF IRUMINANTS.
mistaken for those of a ruminant, and have been referred
to the genus Moschus. One of these interesting transitional
extinct quadrupeds, described in the Geological Journal,
for 1847, under the name of Dichodon, had forty-four teeth
in one uninterrupted series, and of the same kinds, as in
the anoplothere; but the teeth there marked p4, and
mn 1, upper jaw, I have ascertained to be "milk-teeth."
TEETH OF RUMINANTS.
The even-toed or artiodactyle Ungulata, superadd the
characters of simplified form and diminished size to the
more important and constant one of vertical succession in
their premolar teeth. These teeth, in the ruminants, represent only the moiety of the true molars, or one of the
two -semi-cylindrical lobes of which these teeth consist,
with at most a rudiment of the second lobe. An analogous morphological character of the premolars will be
found to distinguish them in the dentition of the genus
Sus (Fig. 75, p2, p 3, p 4), in the hippopotamus, and in the
phacochwerus, or wart-hog, where the premolar series is
greatly reduced in number; yet this instance of a natural
affinity, manifested in so many other parts of the organization of the artiodactyle genera, has been overlooked in
F. Cuvier's work, above cited, although it is expressly
designed to show how much zoological relations are
illustrated by the teeth.
Most of the deciduous teeth of the ruminants resemble
in form the true molars; the last, e. g. has three lobes in
the lower jaw like the last true molar. When, therefore,
the third grinder of the lower jaw of any new or rare
ruminant shows three lobes, the crowns of the premolars




TEETH OF SEALS.               299
should be sought for in the substance of the jaw below
these, and above their opponents in the upper jaw; and
thus the true characters of the permanent dentition may
be ascertained.
The deciduous molars are three in number on each
side, and, being succeeded by as many premolars, the
3-3   3-3
ordinary permanent molar formula is p   3' m 33:
but there is a rudiment of an anterior milk-mplar, d 1, in
the embryo fallow-deer, and in one of the most ancient
of the extinct ruminants (dorcatherium, Kaup) the normal
number of premolars was fully developed.
The molar series of all the Diphyodonts is naturally
divisible into only two groups, premolars and molars;
4 —-4 3 —3
the typical number of these is 4-, --— 3; and each
4-4 3- 3
individual tooth may be determined and symbolized
throughout the series, as is shown in the instances under
Cut 75.
SEAL TRIBE.
(Phocidce). —There is a tendency to deviate from the
ferine number of the incisors in the most aquatic and
piscivorous of the Musteline quadrupeds, viz., the seaotter (enhydra), in which species the two middle incisors of
the lower jaw are not developed in the permanent dentition. In the family of true seals, the incisive formula is
further reduced, in some species even to zero in the lower
jaw, and it never exceeds  -— 2  All the phocidce possess
2 -2
powerful canines; only in the aberrant walrus are they
absent in the lower jaw; but this is compensated by the




300               TEETI  OF SEALS.
singular excess of development which they manifest in
the upper jaw (Fig. 70). In the pinnigrade, as in the
plantigrade family of carnivores, we find the teeth which
correspond to true molars more numerous than in the
digitigrade species, and even occasionally rising to the
typical number, three on each side; but this, in the seals,
is manifested in the upper, and not, as in the bears, in
the lower jaw. The entire molar series usually includes
five, rarely six teeth on each side of the upper jaw, and
five on each side of the lower jaw, with crowns, which
vary little in size or form in the same individual; they
are supported in some genera, as the eared seals (otarice),
and elephant seals (cystophora), by a single fang; in other
genera by two fangs, which are usually connate in first
or second teeth; the fang or fangs of both incisors, canines and molars, are always remarkable for their thickness, which commonly surpasses the longest diameter of
the crown. The crowns are most commonly compressed,
conical, more or less pointed; in a few of the largest
species they are simple and obtuse, and particularly so
in the walrus, in which the molar teeth are reduced to a
smaller number than in the true seals. In these, the line
of demarcation between the true and false molars is very
indefinitely indicated by characters of form or position;
but, according to the instances in which a deciduous
dentition has been observed, the first three permanent
molars in both jaws succeed and displace the same
number of milk molars, and are consequently p-remolars; occasionally, in the seals with two-rooted molars,
the more simple character of the premolar teeth is
manifested by their fangs being connate, and in the
Stonorlhynichus serridenls the more complex character of




TEETH OF QUADRUMANA.               301
of the true molars is manifested in the crown. In the
Stenorhynchus leptontyx, each molar tooth in both jaws is
trilobed, the anterior and posterior accessory curving towards the principal one, which is bent slightly backwards; all the divisions are sharp-pointed, and the crown
of each molar thus resembles the trident or fishing-spear;
the two fangs of the first molar in both jaws are connate.
In the Stenorhyncus serridens, the three anterior molars on
each side of both jaws are four-lobed, there being one
anterior and two posterior accessory lobes; the remaining
posterior molars (true molars) are five-lobed, the principal cusp having one small lobe in front, and three developed from its posterior margin; the summits of the lobes
are obtuse, and the posterior ones are recurved like the
principal lobe. Sometimes the third molar below has
three instead of two posterior accessory lobes. Occasionally, also, the second, as well as the first molar above,
has its fangs connate: but the essentially duplex nature
of the seemingly single fang, which is unfailingly manifested within by the double pulp-cavity, is always outwardly indicated by the median longitudinal opposite
indentations of'the implanted base.
TEETH OF QUADRUMANA.
The chief aim of comparative anatomy being the better comprehension of the structure of man, we shall
finally describe those modifications of the dental system
which throw more immediate light on the nature of the
teeth in the human subject, and which are met with, as
might be expected, in the order (Quadrumana) of mam26




302   TEETH OF ORANG AND CHIMPANZEE.
malia that makes the nearest approach to that represented by the genus homo.
Through a considerable part of the quadrumanous
series, e.g., in all the apes and monkeys of the Old World,
in all the genera, indeed, which are above the lemurs
(cat-monkeys and slow monkeys) of Madagascar, the same
number and kinds of teeth are present as in man; the
first deviation being the disproportionate size of the canines and the concomitant break, or " diastema," in the
dental series for the reception of their crowns when the
mouth is shut. This is manifested in both the chimpanzees and orangs, together with a sexual differenacgin the
proportions of the canine teeth.
In that large ape of tropical Africa, called the "gorilla"
(Troglodytes gorilla), which, in some important particulars,
more resembles man than does the smaller kind of chimpanzee (Troglodytes niger), the dentition seems to approach
nearer to the carnivorous type, at least in the full-grown
male (see Fig. 50, p. 223). It is nevertheless strictly
quadrumanous in its essential characters, as in the broad,
flat, tuberculate grinding surfaces of the molar teeth; but
in the minor particulars in which it differs from the dentition of the orang, it approaches nearer the human type.
In the upper jaw the middle incisors are smaller, the
lateral ones larger than those of the orang; they are thus
more nearly equal to each other; nevertheless, the proportional superiority of the middle pair is much greater
than in man, and the proportional size of the four incisors both to the entire skull and to the other teeth is
greater. Each incisor has a prominent posterior basal
ridge, and the outer angle of the lateral incisors, i 2, is
rounded off as in the orang. The incisors incline forwards from the vertical line as much as in the great




TEETH OF ORANG AND CHIMPANZEE.   303
orang. The characteristics of the human incisors are, in
addition to their true incisive wedge-like form, their near
equality of size, their vertical or nearly vertical position,
and small relative size to the other teeth and to the entire skull. The diastema, between the incisors and the
canine on each side, is as well marked in the male chimpanzee as in the male orang. The crown of the canine
(ib.), c, passing outside the interspace between the lower
canine and premolar, extends, in the male Troglodytes
gorilla, a little below the alveolar border of the under
jaw when the mouth is shut: the canines in both jaws
are twice the size of those teeth in the female gorilla.
Both premolars are bicuspid; the outer cusp of the
first and the inner cusp of the second being the largest,
and the first premolar consequently appearing the largest
on an external view. The anterior external angle of the
first premolar is not produced as in the orang, which, in
this respect, makes a marked approach to the lower quadrumana. In man, where the outer curve of the premolar
part of the dental series is greater than the inner one, the
outer cusps of both premolars are the largest; the alternating superiority of size in the chimpanzee accords with
the straight line which the canine and premolars form
with the true molars.
The three true molars are quadricuspid, relatively
larger in comparison with the bicuspids than in the
orang. In the first and second molars of both species of
chimpanzee, a low ridge connects the antero-internal with
the postero-external cusp, crossing the crown obliquely,
as in man. There is a feeble indication of the same ridge
in the unworn molars of the orang; but the four principal cusps are much less distinct, and the whole grinding
surface is flatter and more wrinkled than in the chim



304   TEETH OF ORANG AND CHIMPANZEE.
panzee. The repetition of the strong sigmoid curves,
which the unworn prominences of the first and second
true molars present in man, is a very significant indication of the near affinity of the gorilla and the chimpanzee,
as compared with the approach made by the orangs or
any of the inferior quadrumana, in which the four cusps
of the true molars rise distinct and independently of each
other. The premolars as well as molars are severally implanted by one internal and two external fangs, diverging,
but curving towards each other at their ends as if grasping the substance of the jaw. In no variety of the human
species are the premolars normally implanted by three
fangs; at most the root is bifid, and the outer and inner
divisions of the root are commonly connate. It is only
in the black varieties, and more particularly that race inhabiting, Australia, that' I have found the wisdom tooth,
or last true molar, with three fangs as a general rule; and
the two outer ones are more or less confluent.
The molar series in both species of chimpanzee forms
a straight line, with a slight tendency in the upper jaw to
bend in the opposite direction to the well-marked curve
which the same series describes in the human subject.
This difference of arrangement, with the more complex
implantation of the premolars, the proportionally larger
size of the incisors as compared with the molars; the still
greater relative magnitude of the canines; and, above all,
the sexual distinction in that respect illustrated by the
skull of the full-grown male gorilla (Fig. 50, p. 223),
stamp the chimpanzees most decisively with not merely
specific but generic distinctive characters as compared
with man. For the teeth are fashioned in their shape
and proportions in the dark recesses of their closed
formative alveoli, and do not come into the sphere of ope



TEETH OF ORANG AND CHIMPANZEE.   305
ration of external modifying causes, until the full size of
the crowns has been acquired. The formidable natural
weapons, with which the Creator has armed the powerful
males of both species of chimpanzee, form the compensation for the want of that psychical capacity to forge destructive instruments which has been reserved as the
exclusive prerogative of man. Both chimpanzees and
orangs differ from the human subject in the order of the
development of the permanent series of teeth; the second
molar, rnu 2, comes into place before either of the premolars has cut the gum, and the last molar, m 3, is acquired before the canine. WTe may well suppose that the
larger grinders are earlier required by the frugivorous
chimpanzees and orangs than by the higher organized
omnivorous species with more numerous and varied resources; and probably one main condition of the earlier
development of the canines and premolars in man may
be their smaller relative size.
In the South American quadrumana, the number of
teeth is increased to thirty six, by an addition of one
tooth to the molar series on each side of both jaws. It
might be concluded, a priori, that as three is the typical
number of true molars in the placental mammalia with
two sets of teeth, the additional tooth in the cebince would
be a premolar, and form one step to the resumption of the
normal number (four) of that kind of teeth. The proof
of the accuracy of this inference is given by the state of
the dentition in any young spider-monkey (Ateles), or
Capucin-monkey (Cebus), which may correspond with that
of the human child in Fig. 76, i. e. where the whole of the
deciduous dentition is retained, together with the first
true molar (mn 1) on each side of both jaws. If the germs
of the other teeth of the permanent series be exposed in
26*




306    TEETH OF 3MONKEYS AND LEMURS.
the upper jaw (as in Fig. 76), the crown of a premolar
will be found above the third molar in place, as well as
above the second and first. As regards number; therefore, the molar series, in the South American monkeys
(Aiycetes, Ateles, Cebus), is intermediate between that of the
genus Miustela and of Felis (Fig. 69); the little premolar,
p i, in Mustela, shows plainly enough which of the four is
wanting to complete the typical number in the South
American monkey, and which is the additional premolar
distinguishing its dental formula from that of the Old
World monkeys and man.
Zoologists have rightly stated, as a matter of fact, that
the little marmoset monkeys (Ilapa le, Ouistiti) " have only
the same number of teeth as the monkeys of the Old.4  1 —1  5-5,, 
YWorld-viz: 32, ic    im_    5.  But the difference
is much greater than this numerical conformity would
intimate. In a young Jacchus penicillatus, I find that
there are three deciduous molars displaced by three premolars, as in the other South American quadrumana, and
that it is the last true molar, m 3, the development of
which is suppressed, not the premolar,p 2, and thus these
diminutive squirrel-like monkeys actually differ from the
Old World forms more than the Cebidce do; i. e. they diffir
not only in having four teeth (p 2 11), which the monkeys of the Old World do not possess, but also by wanting four teeth (m 3 Li), which those monkeys, as well
1 1
as the C(ebicie, actually have. It is thus that the investigation of the exact homologies of parts leads to a recognition of the true characters indicative of zoological
affinity.




TEETI OF MIONKEYS AND LEMURS.    307
3-3  3-3
Most of the Lemurinrce have p3 3   3, together with
remarkable modifications of their incisive and canine
teeth, of which an extreme example is shown in the pectinated tooth of the gct~copithecus. The inferior incisors
slope forwards in all, and the canines also, which are
contiguous to them, and very similar in shape.
In the hoofed quadrupeds with toes in uneven number
(perissodactyla), whose premolars, for the most part, repeat
both the form and the complex structure of the true
molars, such premolars are distinguished by the same
character of development as those of the artiodactyla, or
ungulates, with toes in even number; although here the
premolars are distinguished also by modifications of size
and shape. The complex ridged and tuberculate crowns
of the second, third, and fourth grinders of the rhinoceros,
hyrax, and horse, no more prove them to be true molars
than the trenchant shape of the lower carnassials of the
lion proves them to be false molars. It is by development alone that the primary division of the series of
grinding teeth can be established, and by that character
only can the homologies of each individual tooth be determined, and its proper symbol applied to it.
In Fig. 72, the three posterior teeth of the almost uniform grinhding series of the horse's dentition are thus
proved to be the only ones entitled to the name of "true
molars;" and, if any one should doubt the certainty of
the rule of counting, by which the symbols, p 4, p 3, and
p 2, are applied to the three large anterior grinding teeth
(ib.), which are commonly the only premolars present in
each lateral series of the horse's jaws, yet the occasional
retention of the diminutive tooth (p 1), would establish
its accuracy, whet-her such tooth be regarded as the first




308        HOMOLOGIES OF THE TEETH.
of the deciduous series unusually long retained, or the
unusually small and speedily lost successor (p 1) of an
abortive (d 1).
The law of development, so beautiful for its instructiveness and constancy in the placental diphyodonts, is well
illustrated in the little hyrax, in which the d 1 is normally
developed and succeeded by a permanent, p 1, differing
from the rest only by a graduated inferiority of size,
which, in regard to the last premolar, ceases to be a distinction between it and the first true molar.
The elephant, which by its digital characters belongs to
the odd-toed, or perissodactyle, group of pachyderms, also
resembles them in the close agreement in form and structure of the grinding teeth representing the premolars, with
those that answer to the- true molars of the hyrax, tapir,
and rhinoceros. The gigantic proboscidian pachyderms
of Asia and Africa present, however, so many peculiarities of structure as to have led to their being located in a
particular family in the Systematic Mammalogies. And
this seems to be justified by no character more than by
the singular seeming exception which they present to the
diphyodont rule which governs the dentition of other
hoofed quadrupeds. In fact, the elephant, like the dugong, sheds and replaces vertically only its incisors,
which are also two in number, very long, and of constant
growth, forming tusks, with an analogous sexual difference in this respect in the female of the Asiatic'species.
The molars, also, are successively lost, are not vertically
replaced, and are reduced finally to one on each side of
both jaws, which is larger than any of its predecessors.
These analogies are interesting and suggestive in connection with the other approximations in the "Sirenia" to
the pachydermal type.




HOMOLOGIES OF THE TEETH.              309
In the mammalian orders with two sets of teeth, these
organs acquire fixed individual characters, receive special
denominations, and can be determined from species to
species. This individualization of the teeth is eminently
significative of the high grade of organization of the animals manifesting it. Originally, indeed, the name "incisors," "laniaries," or "canines," and " molars" were given
to the teeth, in man and certain mammals, as in reptiles,
in reference merely to the shape and offices so indicated;
but they are now used as arbitrary signs, in a more fixed
and determinate sense. In some carnivora, e. g. the front
teeth have broad tuberculate summits, adapted for nipping and bruising, while the principal back teeth are
shaped for cutting, and work upon each other like the
blades of scissors. The front teeth in the elephant project from the upper jaw, in the form, size, and direction
of long-pointed horns. In short, shape and size are the
least constant of dental characters in the mammalia; and
the homologous teeth are determined, like other parts, by
their relative position, by their connections, and by their
development.
Those teeth which are implanted in the premaxillary
bones, and in the corresponding part of the lower jaw, are
called " incisors," whatever be their shape or size. The
tooth in the maxillary bone, which is situated at, or near
to, the suture with the premaxillary, is the " canine," as is
also that tooth in the lower jaw which, in opposing it,
passes in front of its crown when the mouth is closed.
The other teeth of the first set are the "deciduous molars;"
the teeth which displace and succeed them vertically are
the " premolars;" the more posterior teeth, which are not
displaced by vertical successors, are the " molars" properly
so called.




310 DECIDUOUS AND PERMANENT TEETH OF HOG.
The hog is one of the few existing quadrupeds which
retain the typical number and kinds of teeth.
Figure 75, part of the lower jaw of a young hog, illustrates the phenomena of development which distinguishes
the premolars from the molars. The first premolar, p 1,
Fig. 75.
DECIDUOUS AND PERMANENT TEETH OF THE HOG.
and the first molar, rn 1, are in place and use, together
with the three deciduous molars, d 2, d 3, and d 4; the
second molar, m 2, has just begun to cut the gum; p 2,
p 3, and p 4, together with rn 3, are more or less incomplete, and concealed in their closed alveoli.
The premolars must displace deciduous molars in order
to rise into place; the molars have no such relations. It
will be observed that the last deciduous molar, d 4, has
the same relative superiority of size to d 3, and d 2, which
m 3 bears to mn 2 and m 1; and the crowns of p 3 and p
4 are of a more simple form than those of the milk-teeth
which they are destined to succeed.
The germ of the permanent canine has not yet appeared
below the deciduous one, c; those of the permanent incisors, i 1, i 2, i 3, are seen ready to push out the deciduous incisors d 1, d 2, d 3. When the whole of the second




HOMOLOGIES OF THE HUMAN TEETH.    311
set of teeth is in place, its nature is indicated by the
formula: —,ck 11,44,  m3           44: which sig3 —3   i-_11 —! 4 7  3 
nifies that there are, on each side of both upper and lower
jaws, three incisors, one canine, four premolars, and three
molars, making in all forty-four teeth; each distinguished
by the symbol marked in the cut.
When the premolars and the molars are below their
typical number, the absent teeth are missing from the fore
part of the premolar series, and from the back part of the
molar series. The most constant teeth are the fourth
premolar and the first true molar; and, these being known
by their order and mode of development, the homologies
of the remaining molars and premolars are determined by
counting the molars from before backwards, e. g., "one,"
"two," " three," and the premolars from behind forwards,
"four," "three," "two," "one."
Examples of the typical dentition are exceptions in
the actual creation; but it was the rule in the forms of
mammalia first introduced into this planet; and that, too,
whether the teeth were modified for animal or vegetable
food.
With regard to the human dentition, the discovery by
the great poet Goethe of the limits of the premaxillary
bone in man, leads to the determination of the incisors,
which are reduced to two on each side of both jaws; the
contiguous tooth shows by its shape, as well as position,
that it is the canine, and the characters of size and shape
have also served to divide the remaining five teeth in
each lateral series into two bicuspids and three molars.
In this instance, the secondary characters conform with
the essential ones. But, since we have seen of how little
value shape or size are, in the order carnivora, in the de



312    HOMOLOGIES OF THE HUMAN TEETtH.
termination of the exact homologies of the teeth, it is
satisfactory to know that the more constant and important
character of development gives the requisite certitude as
to the nature of the so-called bicuspids in the human subject. In Fig. 76, the condition of the teeth is shown in
Fig. 76.
DECIDUOUS AND PERMANENT TEETH, HUMAN, AET. 70
the jaws of a child of about six years of age. The two
incisors on each side, d, i, are followed by a canine, c, and
this by three molar teeth like those of the adult; in fact,
the last of the three, m, is the first of the permanent
molars; it has pushed through the gum, like the two
molars which are in advance of it, without displacing any
previous tooth, and the substance of the jaw contains no
germ of any tooth destined to displace it; it is, therefore,




NOTATION AND SYMBOLS OF TEETH.   313
by this character of its development, a true molar, and
the germs of the permanent:teeth,'which are exposed in
the substance of the jaw, between the diverging fangs of
the molars d 3 and d 4, prove those molars to be temporary, destined to be replaced, and prove also that the teeth
about to displace them are premolars. According, therefore, to the rule previously laid down, we'count the permanent molar in place as the first of its series, m 1, and
the adjoining premolar as the last of its series, and consequently the fourth of the typical dentition, or p 4.
We are thus enabled, with the same scientific certainty
as that whereby we recognize in' the middle toe of the
foot the homologue of that great digit which forms the
whole foot and is incased by the hoof of the horse, to
point to p 4, or the second bicuspid in the upper jaw, and
to m 1, or the first molar in the lower jaw; of man, as the
homologues of the great carnassial, or flesh-cutting teeth
of the lion (Fig. 69). We also conclude that the teeth
which are wanting in man to complete the typical molar
series are the first and second premolars, the homologues
of those marked p 1 and p 2 in the hog. The characteristic shortening of the maxillary bones required this diminution of the number of their teeth, as well as their size,
and of the canines more especially; and the still greater
curtailment of the premaxillary bone is attended with a
diminished number and an altered position of the incisors.
The homologous teeth being thus determinable, they
may be severally signified by a symbol as well as by a
name. The incisors, e. g., are here represented by their
initial letter, i, and individually by an added number, i 1,
i 2, and i 3; the canines by the letter c; the premolars by
the letter p; and the molars by the letter m; these also
being differentiated by added numerals. Thus the num27




314   NOTATION AND SYMBOLS OF TEETH.
ber of these teeth, on each side of both jaws, in any given
species-man, e.g.-may be expressed by the following
brief formula:  2-2  1-1  2-2  3-3         and the
2-2' l'c17 2 —-2,  33= 3;
homologies of the typical formula may be signified by i 1,
i2; c; p 3, p 4; m 1, m 2, n 3; the suppressed teeth being
i3, _p 1, andp 2.
These symbols, it is hoped, are so plain -and simple as
to have formed no obstacle to the full and easy comprehension of the facts explained by means of them. If
these facts, in the manifold diversities of mammalian
dentition, were to be described in the ordinary way, by
means of verbal phrases or definitions of the teeth-e. g.
" the second deciduous molar, representing the fourth in
the typical dentition," instead of d 4, and so on-the description would occupy much space, and would levy such
a tax upon the attention and memory as must tend to
enfeeble the judgment, and impair the power of seizing
and appreciating the results of the comparisons.
Each year's experience strengthens my conviction that
the rapid and successful progress of the knowledge of
animal structures, and of the generalization deducible
therefrom, will be mainly influenced by the determination of the nature or homology of the parts, and by the
concomitant power of condensing the propositions relating
to them, and of attaching to them signs or symbols equivalent to their single substantive names. In my work on
the Archetype of the Skeleton, I have denoted most of the
bones by simple numerals, which, if generally adopted,
might take the place of names; and all the propositions
respecting the centrum of the occipital vertebra might be
predicated of the figure "1" as intelligibly as of "basioccipital."




NOTATION AND SYMBOLS OF TEETH.   315
The symbols of the teeth are fewer, are easily understood and remembered, render unnecessary the endless
repetition of the verbal definitions of the parts, harmonize
conflicting synonymes, serve as a universal language, and
express the author's meaning in the fewest and clearest
terms. The entomologist has long found the advantage
of such signs as eo and i, signifying male and female, and
the like; and it is time that the anatomist should avail
himself of this powerful instrument of thought, instruction, and discovery, from which the chemist, the astronomer, and the mathematician have obtained such important
results.








INDEX,
GLOSSARIAL, EXPLANATORY, AND REFERENTIAL.
A                   neuron a nerve), membranes so
called, 16
Acrodus (Gr. akros extreme, and Archetype of the human skeleton,
odous a tooth), osteodentine of   modifications of the, 215 et seq.
the, 247                        Armadillo, dermal bones of the, 19;
Albatross, cranial development of   teeth of the, 259
the, 222                        Articular, the bone, of fishes, 46
Alisphenoid bone of the python's Artiodactyla (Gr. artios in even
skull, 78                         number, and  dactylos finger),
Amphiccelian type of vertebra (Gr.  family of the, 182; dentition of
amphi both, and koilos concave),  the, 307
98                             Astragalus (Lat. the ankle-bone),
Amphiuma, batrachian (Gr. amphi   133; of the hind foot in quadruabout, and hymen a membrane),   peds, 185, 187
skeleton and limbs of the, 184   Ateles (Gr. ateles imperfect), dentiAnapophysis (Gr. ana backwards,   tion of the, 305
and apophysis springing from), 27 Atlas and  axis vertebrae of the
Anarrhicas lupus (Gr. the wolf-   crocodile, 96
fish), teeth of the, 245        Australian  skull, facial angle of
"Angler," teeth of the fish so called,   the, 224
244
Animals, original substance of, 13;              B
extinct races of, 227
Anoplotherium  (Gr. anoplos un- Balena (Lat. a whale), teeth of the,
armed, and  therion a beast),   258
teeth of the, 297               Balistes (Gr. balios speckled), denAnt-eaters, teeth of the, 238; eden-   tine of the, 247
tulous mammals, 258             Barracuda fish, formidable dentiAnthropotomist (Gr. anthropos a   tion of the, 248
man, and tome dissection), 117   Basioccipital of the python (Gr.
Antibrachial bones (Gr. anti against,   basis the base, and Lat. occiput
and brachia arms), 216           back of the head), 72
Ape, skeleton of the, 210; dentition Basisphenoid bone of the python's
of the, 302                      skull (Gr. basis the base, and
Apodal (Gr. a and podes wanting   sphen and eidos, wedge-shaped), 79
feet), 90                      Bat, skeleton of the, 198
Aponeurotic (Gr. apo from, and Batrachia (Gr. batrachos a frog),
27*




318                           INDEX.
skeleton of the, 64 et seq.  (See    cesses (Lat. calx, or calcaneunm,
FROG.)                             the heel), 133, 146, 147; of the
Bicuspis (Lat. bis twice, and cuspis   hind foot in animals, 185, 187.
a point), shape of the molars, 303  Calcification of the dental process,
Birds, composition of their bones,   286
15; skeleton of, 134 et seq.; wing Canines (Lat. cania a dog), of the
bones of, 141; pelvis and leg    Carnivora, 264; of the horse, 271
bones of, 144; structure of the Capucin monkey, dentition of the,
foot in, 148; mechanism of flight   305
in, 149                          Carapace (Gr. karabos a crab) of
Boa-constrictor, skull of the, 81;   the turtle, 124
jaws of the, 83; section of its Carnivora (Lat. caro flesh, and voro
skull, 90                          to devour), teeth of the, 264
Bones, on the formation and com- Carnivorous mammalia, skeleton of
position of the, 13 et seq.; of the    the, 200
vertebrate animals, 15; their che- Carpal bones of the cod-fish (Gr.
mical composition, 15; matter of,   karpos the wrist), 41, 42; of the
variously disposed, ib.; the blas-   crocodile, 118; in man, 216
tema and cartilage of, 21; the Caudal vertebrae (Lat. cauda the
primitive bases of, 21; the growth   tail), modifications of the, 55, 102
of, 22; structure of, in different Cebus (Gr. kebus a species of monclasses of animals, 24; names of   key), dentition of the, 305
different cells, ib. (see SKELETON); Cellular substance of animals, 13
of the fish, 35 et seq.; of the head, Cement of the teeth, 233
general and special names of, 48; Centrum (Gr. kentron a centre), the
classification of the, 50          centre bone of the vertebra, 26,
Bonito, teeth of the, 242             32, 33; of the parietal vertebra,
Bothriolepis (Gr. bothrion a hollow    called  basisphenoid, 43; called
pit, and lepis a scale), pliciden-   presphenoid, 45
tine of the, 247                 Ceratohyal (Gr. keras a horn, and
Bottle-nose cetacean, teeth of the,   hualos glass), 44, 53
259                              Cercopithecus (Gr. kerkos a tail, and
Bradypus tridactylus (Gr. bradus   pithex an ape), skeleton of the, 211
slow, andlpous a foot; tria three, Cestracion (Gr. kestron a dart), osand daktyloi fingers), bones of   teodentine of the, 247
the, 191                         Cetacea, or Cetacians (Gr. kete a
Brain, the upper or anterior divi-   whale), limbs of the, 151; skelesion of the great trunk of the    ton of the, 153
nervous system, 30               Cetiosaurus (Gr. kete a whale, and
Branchial arches (Gr. branchia the    sattra a lizard), vertebrae of the,
gills), 49                          98
Branchiostegal rays (Gr. branchia Chotodonts (Gr. chaite a bristle, and
the gills, and Lat. tego to cover),   odou a tooth), teeth of: the, 242
44, 50                           Chelonian reptiles (Gr. chelone a
Bruta, order of their numerous   tortoise), osteology of the, 100 et
teeth, 259; dentition of the, 294    seq. (see TORTOISE); masticating
organs of the, 249
Chimmeroids (Gr. chimara a monC                    ster, and eidos resemblance), vasodentine of the, 247
Cachalot, teeth of the, 259         Chimpanzee, cranial development of
Calcaneum bone, or calcaneal pro-   the, 223; dentition of the, 302




INDEX.                             319
Citherinue (Gr. cithara a harp), Dendrodus (Gr. dendron a tree, and
teeth of the, 242                   odous a tooth), dendrodentine of
Clavicles (Lat. clavis a key), 93    the, 247
Cobra, skeleton of the, 74          Dental systems (see TEETH).
Cod-fish, bones of the, 36 et seq.; Dentary, the, 46
its skull, 37; its occipital verte- Dentinal tissues of the teeth, 231
bra, 40                          Dentine (Lat. dens a tooth), the tisCondyloid cavity (Gr. kondylos a    sue forming the body of the tooth,
protuberance, and eidos resem-   230; first modification of, 232;
blance), 145; in birds, 147         disposition of the, 237; modifiConfluent (Lat. confluens flowing to-   cations of, in various genera of
gether), 42                        fishes, 247; of the elephant, 286
Connate (Lat. con and natus born  Dentition (see TEETH).
together), 42                    Dermoskeleton (Gr. derma the skin,
Coracoid bone (Gr. korax and eidos   and skeleton), 16; of the sturcrow-like), 40                     geon, 17; of the armadillo, &c.,
Cottoids (Gr. kotte a head, and eidos   19; chief developments of the,
resemblance),  osteodentine  of   31; the cranial bones, the suprathe, 247                           temporals, the superorbitals, the
Cotyloid cavity (Gr. kotyle a drink-   suborbitals, the lachrymal, and
ing-cup, and eidos resemblance),   the labials, 52
144                              Diapophyses (Gr. dia across, apo
Cranial arches (Lat. cranium  the    from, and phusis growth), bones
skull), 102                        of the vertebra, 26 et seq. smepe;
Cranium  (Gr. kranion the skull),   of parietal vertebra called masapplication of the term, 52; its   toid bone, 43
progressive expansion in various Diastema of the horse (Gr. dia beanimals, 222                       tween, and istemi to stand), 169
Crocodile, osteology of the, 95 et Dicynodon lacerticeps (Gr. di two,
seq.; skeleton of the, 95, 113;   kuon dog, and odous a tooth, and
vertebrae of the, 96; vertebrae of   Lat. lacerta a lizard), skull and
extinct species, 97, 98; its skull,   teeth of the, 253
103 et seq.; its limbs, 115, 117; Dicynodonts (Gr. see ante), dentipelvis and hind-limb of the, 119;   tion of the, 253
its cranial development, 222; its Diodon (Gr. dis double, and odous a
teeth, 256                         tooth), 243, 247
Ctenodus (Gr. odous a tooth), osteo- Diver, tarso-metatarse of the, 148
dentine of the, 247              Dog, cranial development of the,
Cuboides bone (Gr. kubos a cube,   223
and eidos resemblance), 134; cu- Dolphin, teeth of the, 259
boid of the hind foot in animals, Duck, skeleton of the, 141; quill
185, 186                           feathers of the, 144
Cuneiforme, one of the carpalbones, Dugong, skeleton of the, 157
216
Cuvier, Baron, his contempt for
metaphysical theorizing, 221                      E
D                  Ectocalcancal (Gr. ektos out of, and
calcaneum the heel), 147
Dendrodentine (Gr. dendron a tree, Ectocarotid canal (Gr. ekto out of,
and Lat. dens a tooth), in fishes,   and karos stupor), 169
247                              Ectocondyloid surface (Gr. ektos out




320                           INDEX.
of, and kondylos a protuberance), Episternum  (Gr. ut ante), 128; of
146                                the crocodile, 115
Ectocuneiform  (Gr. ektos out of, Epitympanic bone (Gr. epi and tymand Lat. cuneus a wedge), 170;   panon on the drum), 43
of the hind foot in animals, 185, European skull, facial angle of the,
186                                224
Ectometatarse (Gr. ektos out of, Eustachian process (leading from
meta over, and tarsos the palm of   the pharynx to the tympanum, so
the hand or foot), 147             called from  Eustachius the disEctocnemial ridge (Gr. ektos out of,   coverer), 169
and kneme the knee), 145         Ex-occipitals of the python (Lat. ex
Ectopterygoid (Gr. ektos sixth, pte-   from, and occiput the back of the
ryx a wing, and eidos, likeness),   head), 76
angle of the, 80, 82 et seq. seepe.  Exoskeleton (Gr. ex and skeletos the
Edaphodonts (Gr. dapto to tear, and    outer skeleton), 119
odous a tooth), dental masses of
the, 250
Edentata (Lat. edens eating), skele-                P
tons of the, 152, dentition of the,
294                              Fabella (Lat. a little bean) of the
Elephant; its tarsal bones, 187;    sloth, 192
dentition of the, 238, 239, 259, Facial angle, representations of the,
309; its skull and teeth, 273; its   in various animals, 222; of the
tusks and molars, 274 et seq.      Australian and the European, 224
Enamel of the teeth, 233; of the Femur (Lat. the thigh-bone) of the
elephant's tooth, 285               crocodile, 120
Endoskeleton (Gr. endos and skeletos Fibula (Lat. fibula the lesser bone
the inner skeleton), 119           of the leg) of the crocodile, 120;
Entocalcaneal process  (Gr. entos   of the sloth, 198
within, and Lat. calcaneum  the Fins of fishes; structure of the, 55;
heel), 147                         the ventral, 62; general action of
Entocondyloid  cavity  (Gr. entos   the, ib.
within, condylos a protuberance, Fishes, composition of their bones,
and eidos resemblance), 147        14; vertebrae of, 33; skeleton of,
Entometatarse (Gr. entos within,   ib. et seq.; the first forms of vermeta over, and tarsos,' the palm of   tebrate life, 50; arrangement of
the hand or foot), 147             bones in their heads, ib.; modifiEntopterygoids (Gr. entos within,   cations of the jaws of, 51; their
andpterygoidos wing-like), 48, 169    caudal vertebrae, 65; modificaEntosternum (Gr. entos within, and    tions of the fin-rays of, 56; ostesternon the breast-bone), 128      ological structure of their heads,
Epapophysis (Gr. epi above, and    ib.; adaptation of their skull and
apophysis springing from), 28      skeleton to aquatic life, 59, 61;
Epicnemial ridge (Gr. epiupon, and    action of their fins, 63; their
kneme the knee), 145               system, 240; shedding and dental
Epidermoid system  (Gr. epi upon,   renewal of the teeth in, 249
and dermos the skin), 141        Flying lizard, vertebrae of the, 92
Epiphyses (Gr. epi and phuo grow- Foot, distinct bones of the, in difing upon), the ossified ends of   ferent mammalia, 185, 186; law
bones, 22                          of simplification of the, 187
Episternal (Gr. epi and sternon on  Foramina (Lat. foramen an openthe breast-bone), 128              ing), 80




INDDEX.                            321
Frog, skeleton of the, 68, 69, 71;   the pectoral, the branchi-ostegal,
metamorphosis of its skeleton,   the opercular, and the pterygoid,
68; of its skull, 70               51
Frontal segment, or vertebrae, 45.  Haerrial spine of parietal vertebra,
Frontals (Lat. frons the front) of   its divisions-basihyal, glossothe python's skull, 79             hyal, and urohyal, 44
Furculum bone (Lat. furca a fork), Hlemapophyses (Gr. haima blood,
139                                and apophysis springing from),
bones of the vertebra, 27-et seq.
swpe.
G                  Haemapophysis'of the parietal vertebra, its divisions-epihyal and
Galeopithecus (Gr. gale a weasel,   ceratohyal, 44
and pithikos a monkey), teeth of Hallux (Lat. the great tloe), 146
the, 307.                        Head, bones of the, 48; and their
Ganpid,(Gr. 9ganos,brightness), a    classification, 48, 49; structure
term applied to the scales of cer-   of the, in fishes, 56,tain fishes, 19                  Hearing, organ of, 31; in the codGinglymoid condyle (Gr. ginglymos   fish, 43; the petrosal and the,and eidos hinge-like), 46          otosteal of the cod-fish, 43
Graffe, skeleton of the, 170; bony  Hippopotamus (Gr. hippos a horse,,structure of its head, 174         and potamos a river), skeleton of
Glossohyal (Gr. glossa the tongue,   the, 178; tarsal bones of the, 187
and hyoid the bone like the Greek Hog, osteology of the, 180; dentiletter upsilon), 53                tion of the, 310'
Glyptodons (Gr. glupho to engrave, Holoptychius' (Gr.' holos entire, and
and odous a tooth)'of S. America,   ptchos a fold),' plicidentine of,20Q                                the, 247
Gobioids (Lat. gobio a gudgeon, and Hoofed beasts, even'toed, osteologiGr. eidos resemblance), osteoden-   cal characters of, 180'tine of the, 247                 Hoofed  quadrupeds, skeletons of,
Goniodonts (Gr. gonia an angle, and    162
odous a tooth), teeth of the, 242  Hornbill, enormous beak of the, 24
Goose, skeleton of the, 140; quill IHorse, skeleton of the, 162; its
feathers of the, 144               vertebral formula, 164; its tarsal
Gorilla, dentition of the, 302       bones, 185, 186; incisor tooth of
Grinders of the elephant, 281 et seq.   the, 235; herbivorous dentition
Gryllotalpa (Gr. grillizo to grunt,   of the, 270; its upper and lower
and Lat. talpa a mole), bones of   molars, 271; development and
the, 197'                          succession of teeth in the, 272
Human teeth, homologies of the,
313
II                 Hyena, dentition  of  the, 265;
strength of his jaw, ib.
Ihemal arch (Gr. haima blood), of Hybodus, (Gr. hybos hump-backed,
the vertebra, 26, 43 i; of the occi-   an'd odous a tooth),' osteodentine
pital vertebra of the cod-fish', 40;   of the, 247
called the hyoidean arch, 43     Hydromys (Gr. hydor water, and
Hoemal arches of the skull-the    muis a mouse),'259
sapular, the hyoidean, the man- Hyoidean arch (Gr. u-eidos like the
djbular, and the mnaxillary,, 51;   letter U), the name of a himemil
diverging appendages of tlie-      arch, 44, 53




322                           INDEX.
Hyosternal (Gr. hyo, and sternon                    L
the breast bone), 128
Hypapophysis (Gr. hypo below, and Labroids (Gr. labros voracious, and
apophysis springing from), 28       eidos appearance), dentine of the,
Ilyperoodon (Gr. hyper above, and    247
odous a tooth), dentition.of the, Labyrinthodonts (Gr. labyrinthos a
259::      labyrinth, and odous a tooth), a
Hyposternal (Gr. hypo'under; and    singular variety of extinct Batrasternon the breast-bone), 128      chians, 236; teeth of the, ib.
Hypotympanic bone (Gr. hypo and Lachrymals (Lat. lacrymatears), 81
tynipanon under the drum), 45    Lamelliform  teeth of fishes (Lat.
Hyrax (Gr. hyrax the rock rabbit),   lamia a thin plate, and forma
dentition of the, 308               shape), 243
Lancelet-fish, skeletal framework of
the, 25
I                  Lemuridse (Lat. lemur a hobgoblin),
teeth of the, 307
Ichthyosaurus (Gr. ichthus a fish, Lemurs, teeth of, 307
and saura a lizard), vertebrse of Lepidosiren (Gr. 1i's a scalb, and
the, 98                            siren a water-nymph), osteodenIguana, osteology of the, 91, 93      tine of the, 247
Iguanodon (Gr. iguana a saurian  Lepidosteus (Gr. lepis and osteon
reptile, and odous a tooth), den-   bony-scaled), a fish of the Ohio,
tition of the, 252                 19
Iliac bones (Lat. ilia the flanks), 130 Leptobranchii (Gr. leptos slender,
Incisor tooth, magnified section of   and branchos the throat), order
the, 230                           of the, 240
Incisors (Lat. incasdo to cut in), of Limbs of animals, nature of, 183;
the carnivora, 264                 of the protopterus, ib.; of the
Intercondyloid tract (Lat. inter be-   sloth, 189, 192; of the batratween, and Gr. lkondylos a protu-.chians, 65
berance), 146                    Lion, skeleton of the, 198-204; its
Ischium (Gr. ischis the lumbar re-   jaws and'teeth, 263, 264
gion), 131                        Lithophytes (Gr. lithos a stone, and
Ivory, supplied from the discovered   phuton a plant), the food of the
tusks of the mammoth, 275; mus-   Scari, 247
ket-balls often found in, 276    Lizards, osteology of, 91-95; dental
system of, 253
Loggerhead, a species of turtle so
J                    called, 123
Lophioid fishes (Gr. lophos a crest
Jacchus (Gr. iacho to cry aloud),   or mane, and eidos resemblance),
dentition of the, 306               61
Jaws of fishes, modifications'of the  Lophius (Gr. lophos a crest), den53; of the boa-constrictor     tine of the, 247; plicidentine of
53; of the boa-constrictor, 8.3     te4
the, 247
Lumbar vertebrae (Lat. lumbus the
K                    back), 100
Lunare (Lat. one of the carpal
Kangaroo, skeleton of the, 205        bones), 216




INDEX.                           323
M                    292; deductions from the dental
system of the, 296
Macropus elegans, or kangaroo (Gr. Menopome, vertebral skeleton of
makros long, and pous a foot),   the, 65
skeleton of the, 205            Mesocalcaneal process (Gr. mesos
Magnum (Lat. magnus great), one   middle, and Lat. calcaneurn the
of the carpal bones, 216          heel), 147
Mammalia, bones of the, 14, 24; Mesencephalic (Gr. mesos middle,
principal forms of the skeleton in   en in, and kephale the head), 79
the, 151; dental system  of the, Mesocuneiform (Gr. mesos middle,
258, 261                          and Lat. cuneus a wedge), of the
Mammoths, tusks of,discovered in   hind foot in animals, 185, 186
various parts of the world, 275; Mesosternals (Gr. mesos middle, and
molars of the, 278, 279           sternon the breast-bone), 128
Man, limbs of, 151; skeleton of, Mesotympanic bone (Gr. mesos and
209 et seq.; his varied powers of   tympanon the middle drum), 45
action, 213; skull of, 216; his Metacarpal (Gr. meta with, and caradaptation to an erect posture,   pos the wrist), 118
214; modifications of the skele- Metapophysis (Gr. meta between,
ton of, 215; the sole species of   and apophysis springing from), 28
his genus, and the only repre- Molars of the elephant, 274 et seq.;
sentative of his order, 227; his   their succession, 281; their deteeth, deciduous and permanent,   velopment, 284; of the hog, 310
312'                    Mole, skeleton and bones of the, 195
Mandibular arch (Lat. mandibula Monkeys, teeth of, 305
the jaw) of the boa-constrictor, Morse, skull and teeth of the, 266
82                              Mustela (Lat. the weasel), dentition
Manubrium  (Lat. a hilt) of the   of the, 306
mole? 198                       Mycetes (Gr. mukao to howl), denMarmoset monkeys, teeth of the,   tition of the, 306
306                            Mylodon (Gr. mule a grinder, and
Marsupial bones (Gr. marsupion a   odous a tooth), an extinct race of
pouch), 16                        quadrupeds, 188
Mastodon giganteus (Gr. mastos an Myliobates (Gr. myliao to grind,
udder, and odous a tooth), tusks   and batos a thorn), a genus of
of the, 292                       fishes belonging to the family
Mastoid (Gr. mastos and eidos nip-   Raidae, 241; vasodentine of the,
pie-shaped), 78                   247
Maxillary bone (Lat. maxilla the Myonine matter (Gr. myon a musjaw), 48, 52; of the boa-con-   cle) of animals, 13
strictor, 81; diverging append- Myrmecophaga (Gr. myrmos an ant,
ages of the, 219                  and phago to eat), edentulous
Megalichthys (Gr. megas great, and    animals, 258
ichlhus afish), dentine of the, 247 AMyxinoids (Gr. myxa mucus, and
Megalosaurus (Gr. megas great, and   eidos resemblance), teeth of the,
sauros a lizard), tooth of the, 251   241
Megalonyx (Gr. vnegale great, and
onyx a claw), an extinct race of               N
quadrupeds, 188
Megatherium (Gr. mega great, and Narwhal, jaw-bones of the, 258
therion a beast), an extinct race Nasal vertebra, 48; spine of the,
of quadrupeds, 188; teeth of the,   219




324                           INDEX.
Natatorial  birds- (Lat. natatores Orbitosphenoid bones (Lat. orbis a
swimmers), 150                     circle, Gr. sphen a wedge, and
Neural arch (Gr. neuron a nerve) of   eidos resemblance), 45, 80
the vertebrae, 26                Ornithorhynchus  (Gr. ornithos a
Neural arches of the skull-the en-   bird, and rhynchos a beak), teeth
cephalic, the mesencephalic, the    of the, 258
prosencephalic, and the rhinen- Orycteropus (Gr. orykter a digger,
cephalic, 51                       and pous a foot), tooth of' the, 238
Neural spine of parietal vertebra, Os coccygis (Lat. os a bone, and Gr.
called parietal bone, 43; of fishes,   kokkux a cuckoo), 215
ib.                              Os spheno-occipital of the skull, 218
Neurapophysis (Gr. neuron a nerve, Osseous system, primary classificaand apophysis springing from), a    tion of the, 16
neural process, 27 et seq. saepe; Ossicles (Lat. ossiculum  a little
of parietal vertebra, called ali-   bone), 120
sphenoid, 43                     Osteine (Gr. osteon a bone), the
Neurine matter of animals, 13         matter or tissue so called, 13;
Neuro-skeleton, 16, 18; segmental   arrangement of, 21
composition of the, 26           Osteodentine (Gr. osteon a bone, and
Neuro-skeletal segments of verte-   Lat. dens a tooth), 233; in varibroe of the skull-the occipital,   ous genera of fishes,- 247
the parietal, the frontal, and the Osteology (Gr. osteon and logos a
nasal, 51                          discourse on bones), principles
Notation of teeth, 313                of, 13; general and special terms
Notochord (Gr. notos the back, and    in, 221  (see  SKELETON  AND
chorda cord), the embryonic dor-   BONES).
sal gelatinous chord, 33         Otocrane (Gr. ota the  ears, and
cranion the skull), 31
Ourang-outang, skeleton of the,
0                    210; dentition of the, 302
Ox, tarsal bones of the, 185
Occipital vertebra (Lat. occiput the
back part of the head), of the
cod-fish, 40; of the python, 77                  P
Odontoid process of the axis (Gr.
odous a tooth,tand eidon resem- Pachydermata (Gr. pachus thick,
blance), 96                        and dermala skins), dentition of
Olfactory capsule (Lat. oyfacio to   the, 308
smell, and capsula a little cover- Palatine bones or Palatines (Lat.
ing), 81                           palalum the palate), 47
Olfactory lobes, the, 47           Palato-pterygoid process (Lat. paOperculum  (Lat. a covering flap),   latum the palate, and Gr. pterybones of the, 46; consists of four   goidos wing-like), 168
bones, the preopercular, the oper- Parapophyses (Gr. para transverse,
cular, the subopercular, and the    and apophysis a process), 27 et
interopercular, ib.                 seq. sepe.
Ophidia (see SERPENT TRIBE).       Parietal vertebra  (Lat. paries a
Opisthocoelian  type  of vertebrme    wall), 44
(Gr. opisthos behind, and koilos Paroccipitals (Gr. parea from, and
concave), 97                       Lat. occiput back of the head), 132
Optic foramina (Gr. optomai to see, Parrot-fishes, jaws and food of the,
and Lat. foramen an opening), 80    247




INxD E X.                          325
Patella (Lat. a little dish), 133; of Post-frontals of the skull (Lat. post
the sloth, 192                      behind, and frons the forehead),
Pectoral fin of the cod-fish (Lat.   45, 80
pectus the breast), 41            Postglenoid process of the horse
Pelvic arch of the crocodile, 119     (Lat. post behind, and Gr. glene
Pelvis of birds (Lat. pelvis a basin),   the pupil of the eye), 169
144                              Prefrontals of the skull (Lat. pra
Penthdactyle  foot of birds  (Gr.   before, and frons the forehead),
pente five, and daktylos a finger   47, 80
or toe), 148                     Premandibular bone (Lat. pra bePerch, teeth of the, 241              fore, and mandibula the mandiPercoids (Gr. perkos spotted, and    ble), 245
eidos appearance), osteodentine of Premaxillary (Lat. pra before, and
the, 247                            mlaxilla thejaw), process of the, 82
Periosteum  (Gr. peri and  osteon Premaxillary teeth, 245
around the bone), 22             Premolars (Lat. pra  before, and
Perissodactyla  or Perissodactyles    molo to grind) of the carnivora,
(Gr. perissos an odd number, and    264; of the hog, 310
daktylos a finger or toe), 169, Presphenoid bone (Lat. prwe before,
171; the extinct and existing    and Gr. sphen and eidos wedgegenera of, 171; dentition of the,   like), 45; of the python's skull,
307                                79
Petrosal bone (Gr. petros a stone), Pretympanic bone (Lat. pra before,
48                                 and Gr. tympanon a drum), 45
Phalanx (Gr. arow of soldiers), 118 Primarise, the  primary quill-feaPike, skull and teeth of the, 240     thers of birds, 141
Pisiforme bone (Lat. pisum  a pea, Prionodon (Gr. prion a saw, and
andforma form), 118; one of the    odous a tooth), dentine of the,
carpal bones, 216                  247
Pithecus Satyrus (Gr. pithex  an Pristis (Gr. a sawyer), vasodentine
ape), skeleton of the, 210, 211    of the, 247
Plasma (Gr. plasma assimilation), Processes of the skull, 50
the colorless fluid of the blood, 13 Procnemial ridge (Gr. pro before,
Plastron of the turtle, 126           and kneme the knee), 145
Platax (Gr. platus wide), teeth of Procoelian  (Gr. pros before, and
the, 242                           koilos concave) type of vertebrae,
Platycoelian type of vertebrae (Gr.   97
platus fiat, and koilos concave), 98 Prosencephalon (Gr. pros before, en
Pleurapophyses (Gr. pleuron a rib,   in, and kephale the head), 79
and apophysis springing from), Proteus (Gr. proteus a marine deity),
bones of the vertebra, 27 et seq.   skeleton and limbs of the, 184
sTepe.                           Protopterus (Gr. protos the first,
Plicidentine (Lat. plico to knit to-   and pteryx a wing or fin), 64;
gether, and dens a tooth), in vari-   skeleton and limbs of the, 183
ous genera of fishes, 247        Psammodus (Gr. psammos sand, and
Poison-fangs of snakes, 256, 257      odous a tooth), vasodentine of the,
Polypterus (Gr. polu and pteron    247
many-finned), a fish of the Nile, Pseudopus (Gr. pseudos false, and
19                                 pous a foot) of the lizard kind, 91
Porcupine, skull and teeth of the, Pterygoid process (Gr. pteryx and
267                                 eidos wing-like), 48, 168; of the
Porpoise, teeth of the, 259           boa-constrictor, 80
28




326                           INDEX.
Pubis (Lat. pubes the secret parts), Rhynchosaurus  (Gr.  rlyncus  a
131                                snout, and saurus a lizard), jaws
Pulp-cavity of the teeth, 231         of the, 254
Pycnodonts (Gr. pyknos thick, and Rodent mammalia (Lat. rodo to
odous a tooth), dentine of the,   gnaw), teeth of the, 267
247                              Ruminants (Lat: rumino to chew
Python (Greek name of a large   the cud), skeleton of, 169; teeth
serpent, from pytho to poison),   of, 298
osteology of the, 76; skull of the,
78
Q                  Sacral vertebrme (Lat. sacer sacred),
100
Quadricuspid  (Lat. quatuor four, Saurians (Gr. saura a lizard), skeleand cuspis a point) shape of the   ton of the, 93, 94; armed with
molars, 303                        tusks, 254
Quadrumana (Lat. quatuor four, and Scaphoides (Gr. skaphe a skiff, and
manus hands), limbs of the, 151;   eidos resemblance), 133; of the
skeleton of the, 209, 210; teeth    hind foot in animals, 185; one of
of the, 301; of South America,   the carpal bones, 216
304, 305                         Scapula (Lat. scapula the shoulderQuadrupeds (Lat. quatuor four, and    blade), 91
pedes feet), herbivorous, skeleton  Scapular arch (Lat. see ante), 40;
of the, 171, 173; extinct genera   of the crocodile, 117
of, 171, 182; odd-toed, 169; Scapularihe (Lat. scapula), the scaeven-toed,  172,  180;  extinct   pulary feathers of birds, 144
races of, 188                    Scapulo-coracoid arch (Lat. scapula
Quill-feathers of birds, their differ-   the blade-bone, and Gr. korax and
ent names, 143                     eidos crow-like), 116, 117
Scari (Gr. skaroi parrot-fishes), dentine of the, 247; jaws and food
~R                   of the, 247
Sciaenoids (Gr. skia a shadow, and
Radius of the cod-fish (Lat. radius   eidos resemblance), osteodentine
the lesser arm-bone), 41           of the, 247
Raptorial birds (Lat. raptores seiz- Sclerotal bones (Gr. s7cleros hard),
ers), 149                          48
Rasp teeth, 242                    Sclero-skeleton (Gr. skleros hard,
Rattlesnake, vertebra of the, 85;   and skeleton), 16
poison-fang of the, 257; skull of Sclerotic capsule of the eye (Gr.
the, 258                           skleros hard, and Lat. capsula a
Reptilia, or Reptiles (Lat. reptilis   little cover), 81
creeping along), composition of Scomberoids (Gr. skombros amarine
their bones, 14; principal forms   fish, and eidos resemblance), teeth
of the skeleton in, 64 et seg.;   of the, 242
dental system of, 251            Sea-perch, skeleton of the, 38, 52;
Rhinoceros, skeleton of the, 202,   fin-formula of the, 56
203; tarsal bones of the, 167, 187 Seal, skeleton of the, 158; dentiRhizodes (Gr. rhiza a root, and   tion of the, 299
eidos resemblance), dentine. of Secundarike, the secondary quillthe, 247                           feathers of birds, 144




IND TE X.                          327
Senses of animals, nerves of the,   of the ape tribe, and of man, 211;
30, 31.                            terms in osteology, 221; facial
Serpents  (Lat. serpens creeping),   angle, 222; progressive expansion
osteology of, 75 et seq.; skeleton    of the cranium, 222, 223; Ausof the cobra, 74; structure of the    tralian and European skulls, 224;
skull of, 76; the python, ib.;   retrospect of the various forms of
poisonous, skull of, 84            the, 225
Sharks, their adaptation to aquatic  Skull, the four upper or anterior
life, 62; teeth of, 243; osteo-   segments of the osseous system,
dentine of, 247                    30; various segments of, in fishes,
Sheat-fish, teeth of the, 242         40 et seq.; structure of, in serSheep's-head fish, teeth of the, 243    pents, 76; of the python, 78; of
Sight, organ of, 31                   the boa-constrictor, 81; of poisonous serpents, 84; of the lizard,
SKELETON  (Gr. skeletos a dried    92; of the crocodile, 103 et seq.;
body), on the principal forms of   of the sloth, 193; modifications
the, 13 et seq.; composition and   in the skull of man, 216
classification of the bones consti- Skulls of different animals, 222,
tut.ing the, 14, 1.5; the dermo    223; of an Australian and a Euand neuro  skeletons, 16, 17;   ropean, 224
growth of bones, 21, 22, 23; Sloth, skeleton of the, 188; extinct
structure of bones in different   races of the, 188; its habits and
classes, 24; its segmental compo-   aptitudes, 188, 189; limbs and
sition, 26; vertebrae of the, 28,   skull of the, 192; dentition of
33; archetype of the, 29, 30; of   the, 193
the fish, 37 et seq.; general and  Smell, sense of organ of, 31
special names of the bones of the, Snakes, poisonous, teeth of the, 257
49, 50; principal forms of the, in Sparoids (Gr. sparos a sea-fish, and
the class Reptilia, 64; of the    eidos resemblance), dentine of the,
frog, 65 et seq.; the serpent tribe,   247
75; the lizard, 91; the crocodile, SphyrSena (Gr. the hammer-fish),
95 et seq.; of Chelonian Reptiles,   teeth of the, 244; dentine of
122; of birds, 134; of the class   the, 247; formidable dentition of
Mammalia, 151; of the Cetacea,   the, 247
158; of the seal and walrus, 158, Spider-monkey, dentition of the, 305,
159; of hoofed quadrupeds, 162; Splanchno-ske'eton (Gr. splanchnct
the horse, 163; the rhinoceros,   the bowels), 16; its various parts
167; the giraffe, 170; of herbi-   -the petrosal, the sclerotal, the
vorous quadrupeds, 172; the ca-   turbinal, the branchial, and the
mel, 174; the hippopotamus, 178;   dental, 51
the hog tribe, 180; even-toed Splint-bone, one of the carpal bones,
hoofed beasts, ib.; nature of limbs,   186
183; of the protopterus, ib.; limbs Spurike (Lat. spurius illegitimate),
of the amphiuma, the proteus, the   the bastard feathers of birds, 144
horse, the ox, the rhinoceros, the Sting-ray, jaws and teeth of the, 247
hippopotamus, the elephant, 184, Sturgeon, skeleton of the, 15, 16,
185; of the feet, 185; of the sloth,   17; its habits, 18
188; of the ant-eater, 193; of the Suborbital bones (Lat. sub and ormole, 194; of the bat, 199; of the    bita under the orbit), 49
carnivorous mammalia, 200; of Superorbital bones (Lat. super and
the lion, 201; of the kangaroo,   orbita above the orbit) of fishes,
205; of the quadrumana, 209;   119




328                           INDEX.
Supertemporal bones (Lat. super and    298; of the seal tribe, 299; of
tempora above the temples), 49      the quadrumana, 301; of the
Suprascapular  of  the  crocodile   orang and chimpanzee, 305; of
(Lat. supra above, and scapula   monkeys and lemurs, 306, 307;
the shoulder-blade), 115     heomologies of, 308, 312; of the
Swan, skeleton of the, 137, 138;   hog, 310; notation and symbols
calcaneal prominence of the, 146    of, 313
Sword-fishes, premaxillaries of the, Tentorium (Lat. a tent), 16
53                               Tibia (Lat. the shin-bone) of the
Symbols of teeth, 313                 crocodile, 120; of the sloth, 192
Symphysis  (Gr. son11 and physis Toes, of birds, 146
growing together), 131           Tooth, human, magnified section of
the, 232
Tooth-pulp, the primary basis of
T                    the tooth, 231
Tortoise, osteology of the, 122 et
Tadpole, metamorphoses of the, 68,   seq.; skeleton of the, 123; cara69  ~                              pace and plastron of the, 124,
Tarsal bones (Gr. tarsos the palm of   126; vertebrve of the, 129; skull
the hand or foot), of different   of the, 131; limbs of the, 133
mammalia, 185, 187               Trapezium  (Gr. trapezion a fourTarso-metatarse  (Gr. tarsos the    sided geometrical figure), one of
palm of the hand, and meta over),   the carpal bones, 216
146; modifications of the, 146    Trapezoides (Gr. trapezion Cut ante]
Taste,- organ of, 31                  and eidos resemblance), one of
Tectrices (Lat. tectum a covering),   the carpal bones, 216
the wing coverts of birds, 144    Trochanter (Gr. trochao to turn), of
the crocodile, 120
TEETH, on the principal forms and  Trochlea, tibial (Gr.  trochos  a
structures of the, 229 et seq.; in-   wheel), 1.45
timately related to. the food and Troglodytes (Gr. trogle a cavern,
habits of the animal, ib.; vascu-   and dune to dwell in), facial anlar canals of the, 231; dental   gle of the genus, 227
tissues and pulp-cavities, 231; Turbinal bones, or Turbinals (Lat.
chemical and structural composi-   turbo a top), 48; of the skull, 80
tion of, 234; cement and enamel Turtle, osteology of the, 122; caraof the, ib.; complex and com-   pace of the, 124; plastron of the,
pound teeth, 235; dental system    126
of fishes, 240 et seq.; shedding  Tusks of the elephant and the manmand renewal of, in fishes, 250; of   moth, 274, 278
reptiles, 250, 251 et seq.; of croco- Tympanic bone (Gr. tympanon  a
diles and poisonous snakes, 257;   drum), 46, 53; of the boa-conof mammalia, 258; form, fixation,   stricter, 82
and structure o?, in the mammalia, 259-261 et seq.; of the carnivora, 264; of the morse and the                   U
porcupine, 26i6, 267;  of the
horse, 271; of the elephant, 272- Ulna of the cod-fish (Lat. ulna the
290; their succession, develop-   elbow), 41, 42
meat, &c., 281, 284; of the me- Unciforme (Lat. uncus a hook, and
gatherium, 292; of the anoplo-   forma shape), one of the carpal
theriuin, 29)7; of the ruminants,   bones., 216




INI)EX.                            829
UTnguiculator (Lat. ma2nl is a claw),   bat, 198; of the lion, 201, 202:
limbs of the, 151                   of the kangaroo, 207
Unguinal phalanges (Lat. unguis a Vertebrata (Lat. vertebra a turning
claw, and Gr. phalanx a row of   joint), the highest division of the
soldiers), 119                     animal kingdom, 14; the four
Ungulata (Lat. uneula a hoof), limbs   classes of, 14, 15; composition
of the, 151                        of their bones, ib.
Urohyal (Gr. ouron urine), 53      Vertebrated animals, their successive transmutations, 226
Vespertilio murinus (Lat. the com-'~ mon bat), skeleton of the, 199
Villiform teeth, 241
Varanus, osteology of the, 91, 93; Vomer (Lat. a ploughshare), 47, 80
dentition of the, 251
Vascular canals of teeth, 231
Vasodentine (Lat. vasum a vessel,                  W
and dwns a tooth), 233; in various
genera of fishes, 247            Walrus, skeleton of the, 159
Vertebra  (Lat. verto to turn, or Water-rats of Australia, dentition
vertebra a turning joint), a gene-   of the, 259
ral term  for the vertebral seg- Whale, its skeleton, 153; its teeth,
ments of the skeleton, 221; the    258
parietal and thoracic, 28; auto- Wing of the duck tribe, 143
genous and exogenous parts of Wolf-fish, teeth of the, 245, 246
the, 27, 28; frontal segment, 45; Wrasse, teeth of the, 243
parietal, 44
Vertebrae of the neuroskeleton, 26;
various modifications of the, 28;                X
development of the, 33; the caudal, modifications of the, 55; of Xiphisternum (Gr. xiphos a sword,
the ophidian  reptiles, 84, 86;    and sternon the breast bone), 128
of the lizard, 91; of the crocodile, 95 et seq.; various types of,
97 et seq.; lumbar and sacral, of                Z
the crocodilia, 100; caudal, 102;
of the tortoise, 129; of the swan, Zygantium, 86
139; formula of the, in herbivo- Zygapophysis (Gr. zugos junction,
rous quadrupeds, 175; of the    and apophysis springing from), 27
THE END.








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2          BLANCHARD & LEA'S MEDICAL PUBLICATIONS.
BLAKISTON (PEYTON), M. D.-PRACTICAL OBSERVATIONS ON CERTAIN DISEASES OF THE CHEST,
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COPLAND (JAMES), M. D.-OF THE CAUSES, NATURE, AND TREATMENT OF PALSY AND APOPLEX2Y,
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BLANC/HARD & LEA'S MEDICAL PUBLICATIONS.                              3
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CARPENTER (WILLIAM B.), MI.D.-A  PRIZE ESSAY ON THE USE OF ALCOHOIC LTTQUORS IN
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COOPER (STR ASTLE,,Y P.)- A TREA fIT', O-; T)TSTOCATIONS AND FRACTUrES OF THE JOINTS.
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4           BLANCHARD & LEA'S MEDICAL PUBLICATIONS.
COOPER (SIR ASTLEY P.)-ON TnE STRUCTURE AND DISEASES OF THE TESTIS, AND ON TEE
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CHURCHILL (FLEETWOOD), M.D. —ESSAYS ON THE PUERPERAL FEVER, AND OTHER DISEASES
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DEWEES (W. P.), MN. D.-A COMPREHENSIVE SYSTEM OF MIDWIFERY. Illustrated by occasional
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DEWEES (W. P.), H. D.-A TREATISE ON THE PHYSTCAL AND MEDICAL TREATMENT OF CHILDREEN.
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DUNIGLISON, FORBES, TWEEDTE, AND CONOLLTY. —TIE CrcLoPEnxTA OF Ptn'CTIC.\T, HIEn-T
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** *This work contains no less than four hundred and eighteen distinct treatises, cont-' -
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DUNGLISON (ROBLEY), M. D.-GENERAL THERAPEUTICS AND MATERIA MEDICA; adapted for a
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DICKSON (S. IH.), M. D.-ELEMENTS OF MEDICINE: a Compendious View of Pathology and
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DAY (GEORGE E.), M. D.-A PRACTICAL TREATISE ON THE DOMESTIC MANAGEMENT AND MORE
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ELLIS (BENJAMIN), M.D. —THE MEDTICAL FORMULARY; being a Collection of Prescriptions,
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EPRICHSEN (JOHN). —TIE SCIENCE AND ART OF SURGERY; being a Treatise on Surgical Inju.
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FLINT  (AUSTIN), M. D.-PHYSICAL EXPLORATION AND DIAGNOSIS OF DISEASES AFFECTING THE
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C ROSS (SAMUEL D.),'M.D.-A PRACTICAL TREATISE ON FOREIGN BODIES IN THE AIR-PASSAGES.
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GROSS (SAMUEL D.), M. D.-A SYSTEM OF SURGERY; Diagnostic, Pathological, Therapeutic,
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GLUGE (GOTTLIFEB, AM. D.-AN ATLAS OF PATHOLOGICAL HISTOLOGY. Translated, with Notes
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ITHARRISON (JOIIN), MI. n. - AN ESSAY TOWARDS A CORRECT THEORY OF THE NERrVOUS SYSTETI.
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*,~ Pll,licifing in li0'"h'rdicra! N(:ws and Ti,rary" for'IS38.




BLANCIARID & LEA'S AMEDICAL PUBLICATIONS.                                    7
HAMIILTON (FRANK II.) —h TREATISE  ON FRACTURES AND DISLOCATIONS. In one handsome
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JONES (T. WIIARTON), F. R. S.-TuE PRINCIPLES AND PRACTICE OF OPIITHALMIC MEDICINE AND
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JONES (C. HANDFIELD), F. R. S., AND EDWARD IH. SIEVEKING, M.D. —A MIANUAL OF
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KIRKES (WILTIIAMI SENHOUSE), M. D., AND JAMES PAGET, F. R. S. —A  MANUAL OF
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KNAPP (F.), PH. D.-TEcuNOLOtGY; or, Chemistry applied to the Arts and to Manufactures.
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LEHMANN  (G. C.).-P PYSIOLtoGICAL CHEMISTRY.  Translated from  the second edition b3
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LEIIMNANN' (G. C.). - MA.NUAL OP CHETIICAL PHYSIOLOGY. Translated from the German, with
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IA ROCIIE (R.), M. D.-PNEC,1ONIA; its Supposed Connection, Pathological and Etiological,
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Malaria. "In one handsome octavo volume, extra cloth, of 500 pages.
T,A ROCIIE (IR.) 31. D. —Yzl,Tow FEVER.r considered in its Itistorical, Pathological, Etiological,
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A           BLANCHARD & LEA'S MEDICAL PUBLICATIONS.
LA'tfLA;IAND (M.). —Tnr CAUSES, SYMIr`TOMIS, AND TRmEATIMENT OF SPEIsnATORRt(EnA. Translated
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LARDNER (DIONYSIUS), D. C.. —HANDBOORS OF NATURAL PHILOSOPHY AND ASTRONOCY.
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MORLAND (W. W.), M. D.-DISEASES OF THE URINARY ORGANS; a Compendium of their Diagnosis, Pathology, and Treatment. With Illustrations. In one large and handsome octavo
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MEIGIS (ChtARLES D.), Ai. D.-W-'OMAN: HER DISEASES AND THEIR REMETIES. A Series of [cetures to his Class. Third and improved edition. In one large and beautifully-printed
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MIEIGS (CHARLES D.), M. D. — A TREATISE ON ACUTE AND CHr.ONIC DISEASES OF THE NECK OF
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MALGAIGNE (J. F.). - OPERATIVE SURGERY, based on Normal and Pathological Anatomy.
Translated from the French, by Frederick Brittan, A. B., AI. 1). With numerous illustrations on wood. In one handsome octavo volume of nearly 600 pages.
MOIIR (FRANCIS), PH. D., AND REDWOOD (TIIEOPHIILUS).-PReACTICAL PHARMIACY. Comprising the Arrangements, Apparatus, and Manipulations of the Pharmaceutical Shop and
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Copies can be sent by mail, in five parts, done up in stout covers,
MILLFTER (HENRY), B-. D.-PRINCIPLES AND PRACTICE OF OBSTETITCS; including  the Treatment of Chronic Inflammation of the Cervix and Body of the Uterus, considered as a frequent Cause of Abortion. With about 100 engtravings on wood. in one very huandsetne
xetavo volume of over 600 pages. (iNo)t Rctcdy.)




)BLANCIIARD & LEA'S MEDICAL PUBLICATIONS.                              9
MONTGOMERY (W. F.), M. D., &c. —AN EXPOSITION OF THE SIGNS AND SYMPTOMS OF PREGNANCY. With some other Papers on Subjects connected with Midwifery. From the second
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MIAYNE (JOHIN), M.D. —A DISPENSATORY AND THERAPEUTICAL REMEMBRANCER. Comprising
the entire lists of Materia Medica, with every Practical Formula contained in the three
British Pharmacopoeias. In one 12mo. volume, extra cloth, of over 300 large pages.
MACKENZIE (NVW.), I, D. - A PRACTICAL TREATISE ON DISEASES AND INJURIES OF THE EYE. To
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NEILL (JOHN), M. D., AND FRANCIS GURNEY SMITH, M. D.-AN ANALYTICAL COMPEN.DIUM OF TIlE VARIOUS BRANCHES OF MEDICIL SCIENCE; for the Use and Examination of Students. Second edition, revised and improved. In one very large and handsomely printed
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NELIGAN (J. MOORE), MI.D. —ATLAS OF CUTANEOUS DISEASES. In one beautiful quarto
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NELIGAN (J. MOORE), MI. D. -A PRACTICAL TREATISE ON DISEASES OF THE SKIN. In one neat
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OWEN (PROF. R.) —ON THE DIFFERENT FORMS OF THE SKELETON. One royal 12mo. volume,
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PARKER (LANGSTON).-THnE MODERN TREATMENT OF SYPHILITIC DISEASES, BOTH PRIMARY AND
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PEREIRA  (JONAThIAN), 3I. D. —THE ELEMENTS OF MIATERIA MBEDICA AND THERAPEUTICS.
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PARRITSIT (EDWARD).-AN INTRODUCTION TO PRACTICAL PHARMACY. Designed as a Text-book
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PEASELEE (E. R.), W. D.-TlUMAN IHISToLOGY, in its Applications to Physiology and General
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PIRRIE (WILLIAMI), F.R.S.E. —TE PRINCIPLES AND PRACTICE OF SURGERY. Edited by John
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10          BLANCHARD & LEA'S MEDICAL PUBLICATIONS.
RICORD (P.), M. D.-ILLUSTRATIONS OF SYPHILITIC DISEASE. Translated from the French, by
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FTILIJ (ALFRED), I. D. —PRINCIPLES OF THERAPEUTICS. In one handsome volume. (P'resarhing.)
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BLANCIIARD & LEA'S MEDICAL PUBLICATIONS.                            11
SOLLY (SAMUEL), F.R.S. —THE IIUMAN BRAIN; its Structure, Physiology, and Diseases
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SCtI(EDLER (FRIEDRICH), PH. D.-TTE Boox OF NATURE; an Elementary Introduction to
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TAYLOR (ALFRED S.), M. D., F. R. S.-MEDICAL JURISPRUDENCE. Fourth American, from the
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TANNER (T. H.), M. D. —A MANUAL OF CLINICAL MEDICINE AND PHYSICAL DIAONOSIS. To which
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-  Gentlemen who have the earlier portions of this work can still complete their copies,
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WATSON (TIIOMAS), MI. D., &c. - LECTURES ON THE PRINCIPLES AND PRACTICE OF PHYSIC.
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WHAT TO OBSERVE AT THE BEDSIDE AND AFTER DEATH, IN MEDICAL CASES. Published under the
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WILDE (W. R.).-AURAL SURGERY, AND THE NATURE AND TREATMIENT OF DISEASES OF THE EAR.
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WHITEHEAD (JAMES), F. R. C. S., &c. - THE CAUSES AND TREATMENT OF ABORTION AND STERILITY; being the Result of an Extended Practical Inquiry into the Physiological and
Morbid Conditions of the Uterus. Second American Edition. In one volume, octavo, 368
pages
WEST (CHARLES), M.D. -LECTIRES ON THE DISEASES OF INFANCY AND CHILDHIOOD. Second
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500 pages.




12         BLANCHARD & LEA'S MEDICAL PUBLICATIONS.
WEST- (CTIARLES), M. D.-AN INQUIRY INTO THE PATTIOLOGICAL I'MPORTANCE OF ULCERATION OP
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WEST (CIIARLES), M. D. —LECTURES ON THE DISEASES OF WoMlEN. In two Parts. Part I.,
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WILSON (ERASMUS), M.D., F. R. S.-A SYSTEM OF HUMAN ANATOMY, General and Special.
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WILSON (ERASMIUS), MI. D., F. R. S.-THE DISSECTOR'S MANUAL; Practical and Surgical Anatomy. Third American, from the last revised and enlarged English edition. Modified and
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WILSON (ERASMUS), M. D., F. R. S.-ON DISEASES OF THE SKIN. Fourth American, from the
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WILSON (ERASMIUS'), M. D., F. R. S.-HEALTIIY SKIN; a Treatise on the Management of the
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WILLIAMS (C. J. B.), M.D., F.R.S.-PRINCIPLES OP MIEDICINE; comprising General Pathology
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YOUATT (WILLIAM), V. S. - THE IORSE. A new edition, with numerous illustrations;
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Essay on the Ass and the Mule. By J. S. Skinner, formerly Assistant Postmaster-General,
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YOUATT (WILLIAM), V. S.-THE Doe. Edited by E. J. Lewis, NI.D. With numerous and
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