852 
ZOOLOGY. 
Birds possess three pectoral muscles, arising chiefly from 
their enormous sternum, and acting on the head of the hu¬ 
merus. The first, or great pectoral, weighs, of itself, more 
than all the other muscles of the bird together. The keel 
of the sternum, the fork, and the last ribs, give origin to it; 
and it is inserted in a rough projecting line of the humerus. 
By depressing that bone, it produces the strong and violent 
motions of the wing, which carry the body forwards in 
flying. The middle pectoral lies under this; and sends 
its tendon over the junction of the fork, with the clavicle and 
scapula, as in a pulley, to be inserted in the upper part of 
the humerus; which bone it elevates. By this contrivance 
of the pulley, the elevator of the wing is placed at the under 
surface of the body. The third, or lesser pectoral muscle, 
has the same effect with the great pectoral, in depressing the 
wing. 
One of the flexor tendons of the toes of birds (produced 
from a muscle which comes from the pubis) runs in front of 
the knee; and all these tendons go behind the heel; hence 
the flexion of the knee and heel produces mechanically a 
bent state of the toes, which may be seen in the dead bird; 
and it is by means of this structure that the bird is supported, 
when roosting, without any muscular action. 
This circumstance of the flexion of the toes accompanying 
that of the other joints of the lower extremity of birds, was 
long ago observed by Borelli, and justly attributed by him 
to the connexion which the flexors of the toes have with the 
upper parts of the limb, by which they are mechanically 
stretched when the knee is bent. 
Fig. 35. Muscles of the falco nisus; a, biventer cervicis; 
b, trachelo-occipitalis; c, trachelo-mastoideus; d, cervica- 
lis descendens; e, longus colli; f, sterno-mastoideus; g, mylo- 
hyoideus; h, conicus ossis hyoidei; i, temporalis; k, levator 
coccygis; 1, lateralis coccygis posterior; m, depressor coc- 
cygis; n, o, lateralis coccygis anterior; p, femoro-coccy- 
geus; **, os pubis; q, multifidus spin* ; r, levator costas ; 
s, serratus anticus major; t, coslo-scapularis; u, u, latis- 
simus dorsi; v, trapezius; w, rhomboideus; x, pectoralis 
major; y, pectoralis minor; z, humero scapularis; a, teres; 
b, tensor fasciae-antibrachii; c, deltoideus; d, biceps; e, 
anconaei; f, adductor carpi radialis; g, ulnaris; h, adduc¬ 
tor carpi ulnaris; i, abductor digitorum ; k, abductor exter- 
nus digiti maximi; /, vastus extern us; m, biceps femoris; 
n, semi tendiuosus; o, rectus femoris; p, glutseus medius; 
q, gemelli; r, extensor metatarsi extern us; s, flexor digito¬ 
rum ; vi, accessory flexor of the toes, the tendon of which 
passes over the knee; 1, the oesophagus; 2, the trachea; 
3, the os hyoides; 4, the clavicle; 5, the furcula; 6, the 
scapula; 7, the humerus; 8, the sternum; 9, ulna; 10, 
radius. 
The skeletons of the different mammalia, particularly the 
four-looted ones, vary considerably; yet these varieties may 
be included, at least for the greatest part, under the following 
peculiarities; which serve to distinguish their skeletons from 
those of birds. 
The skeletons of mammalia possess: 
1. A skull with genuine sutures (at least with very few 
exceptions; as perhaps the elephant, and the duck-billed 
auimal, ornithorhynchus). 
2. Jaws furnished witli teeth; except the ant-eaters, the 
manis, the duck-billed animal, the balaena (whale). 
3. An immoveable upper jaw. 
4. An os intermaxillare. 
5. Two occipital condyles. 
G. Seven cervical vertebra; except the three-toed sloth, 
and some cetacea. 
7. Moveable dorsal vertebra. 
8. A pelvis closed in front; except the ant-eaters; which 
have it open; and the cetacea, which have none. 
9. True clavicles in a few genera only. 
The number of proper bones of the cranium is, on the 
whole, the same as in the human subject. The os frontis, 
however, in most of the horned animals, is composed of 
two equal portions; in many of these the two parietal 
bones are consolidated into one, and in others they are 
united to the occiput. Some of the digitata have a peculiar 
flat hone situated transversely between the parietal and occi¬ 
pital bones. 
As the forehead of man is peculiarly distinguished by the 
beauty of its convex superficies, so is that of many of the 
quadrumana, as the larger animals of the monkey tribe, 
papio mormon, &c. by the large flat triangular surface into 
which it is compressed, and the sides of which converge 
from the processus malares at the external angles of the orbits, 
obliquely backwards, towards the crista occipitalis. 
A principal variation in the form of the cranium arises 
from the size and direction of the crista occipitalis, which 
bears a determinate proportion to the strength of the jaws. 
The situation and direction of the great occipital foramen 
are attended with remarkable variations in some instances. 
Instead of being situated far more anteriorly, and for the most 
part horizontally, as in the human subject, (in which indeed 
the anterior margin is sometimes higher than the posterior,) 
it is placed, in most quadrupeds, at the base of the cranium, 
and obliquely, with the posterior border more or less turned 
upwards. In some, indeed, its direction is completely ver- 
tical ; and in the marmot of the Alps its upper margin is 
turned more forwards than the lower. 
The true sutures, which connect the individual bones of 
the cranium, are generally less intricate, at least to outward 
appearance, in quadrupeds than in man. Their indentations 
are very strong and sharp in the horned pecora, for obvious 
reasons ; and the frontal bones are thick in the same animals. 
The ossicula wormiana are seldom seen in the crania of ani¬ 
mals, yet Blumenbach has specimens of these in the hare and 
a young orang-outang. 
The general form of the cranium is most materially in¬ 
fluenced by the direction, and the various degrees of promi¬ 
nence of the facial bones. The projection is generally formed 
by a prolongation of the upper jaw ; partly also, and in many 
instances chiefly, by the os iutermaxillare, which is inclosed 
between the two upper jaw-bones. See for a more full ac¬ 
count of this difference the articles Man, Physiology, 
and Physiognomy. 
The upper jaw-bones of other mammalia do not, as in 
man, touch each other under the nose, and contain all the 
upper teeth; but they are separated by a peculiar single or 
double intermaxillary bone, which is in a manner locked be¬ 
tween the former, and holds the incisor teeth of such animals 
as are provided with these teeth. 
The want of the os intermaxillare has been regarded as a 
chief characteristic of the human subject; as one of the lead¬ 
ing circumstances which distinguish man from other mam¬ 
malia. 
That all other mammalia possess this bone, is not quite so 
clear as that it is wanting in man. The exceptions occur in 
the quadrumana : as the orang-outang for example. 
The anterior palatine holes, or foramina incisiva are double 
in most mammalia, as in man. They are much larger in 
quadrupeds than in the human subject: in the pecora and 
the hare they are remarkably long and broad. 
In the zygoma we observe several important differences, 
immediately derived from the organs of mastication. It is 
of immense strength, and includes a large space towards the 
cranium, for lodging the powerful muscles which move the 
lower jaw, in several carnivorous animals, as the tiger, and 
in some glires, as the beaver It is wanting in the ant-eater, 
in which the temporal and malar bones have only a slight 
projection instead of the usual zygomatic process. This cir¬ 
cumstance is sufficiently explained by the want of teeth, and 
the consequent want of mastication. 
The elephant possesses only a rudiment of the nasal bones. 
In most apes, and even in the orang-outang, there is a single, 
triangular, and very small nasal bone. In the greater num¬ 
ber of true quadrupeds, there are two ossa nasi, frequently of 
very considerable magnitude. This is the case in the pecora 
and hare; also in the horse, pig, &c. In the rhinoceros, the 
ossa nasi, which support the horn, are very soon consolidated 
together. 
In mammalia which have horns, these parts grow on par¬ 
ticular 
