31 
THE MAMMALIA— MAN AND BEASTS. 
Hice in tKe organs by which their movements arc effcctcfij ami, consequently, the 
skeletons exhibit many important peculiarities when compared with those of Man, and 
with each other. Yet, whatever differences may be found to prevail, one general 
cliaractcr can be discovered throughout the whole. The same bones which compose 
the arm and hand of Man, or of the Monkey tribe, are found equally in those genera 
which use their fore extremities for walking, swimming, or flying; the proportions of 
the bones being only altered, or some of the parts being obliterated, or changed. Wc 
find them equally in the fore-leg of the Deer, in the wing of the Hat, and in the fin 
of the Whale. One order of aium.als having an abdominal pouch for containing the 
young, are supplied with two additional bones, called marsupialy moved by appropriate 
nmsclcs. 
The interior composition in the bones of the Mammalia is generally the same; hut 
their texture varies, being denser and closer in the smaller tribes, but very fibrous, 
and loosely arranged in the Cetacea. The texture of the bones in the sea-beasts 
’.3 particularly adapted for locomotion in water, being aided by the lightness of their 
structure, and by having all tlie cells of their bones filled with an oily fluid. 
The joints or articulations by which the bones of the Mammalia are connected to- 
gether greatly influence tlie habits and general economy of these animals. Some of the 
joints are only capable of performing an imperfect motion, while a greater latitude is 
assigned to others. Appropriate iianios have boon assigned to these several kinds of 
articulations, and they have been further arranged in divisions and sub-divisions. 
Some kinds of arliculaiion are obsevveil to be altogether peculiar to certain classes of 
Mammalia; wijilc it frequently occurs that the corresponding bones will vary in their 
mode of ai*ticulation for different MaiuuiaUa. Other bones again, whicli are separated 
in one genus, will be intimately and closely united together in another. 
The first class of articulation (DinrthroMs) contains the free and perfect joint. 
The opposite surfaces of the bones are distinct and well defined, being covered with 
a polished and smooth cartilage. A continuation of the periosteum or external cover- 
ing of each bone passes onwards from mio to the other, forming a kind of cap.sule, or 
little bag, and permitting nothing cither to pass within or to escape from the cavity. 
Hut the periosteum docs not cover the articular cartilages, it merely forms the exter- 
nal covering of the entire joint. Other ligaments frequently strengthen this covering 
either externally or within the capsule, and thus will limit the motions of the bones 
more perfectly tfian the capsule alone could have done. The interval within the cap- 
*ulc is occupied by an oily fluid, or else each bone is covered by a smooth and polished 
cartilage. Sometimes a piece of cartilage will be found; perhaps also some peculiar 
gland, or other solid body. 
The direction and extent of motion possessed by the bones of the Mammalia is 
dependent upon the rigidity or number of the ligaments, as well as upon the form and 
depressions found in the articulated surfaces. 
When a bone is articulated to another by one of its extremities, it admits only of 
two species of motion, torsion or flexion. 
The torsion, or twisting, takes place when the bone is capable of moving round its 
<>'vn axis, or else round an imaginary axis passing through the articulation. This 
kind of motion can only be found when the articulated surfaces are plain or spherical, 
^ud the latter are alone capable of motion in every direction. Flexion or bending 
takes place when the extremity of the bone, farthest from the joint, approaches the 
tone which is fixed. 
The different kinds of torsion have been assigned different names; there is the 
hinge-joint (GingUmufi)i the ball and socket-joint (J^narthrosis or Arthrodia)y and 
tho rotating joint (Trochmdo.s), 
The manner in w liieli the head is attached to the trunk, the lower jaw to the head, 
and the several pai-ts of tho limbs to each other, differs in the several classes of ani- 
w»als. The head of the Mammalia is united by a hinge-joint to the neck ; in the 
Hirds it is connected by u ball and socket-joint. Even among the Mammalia them- 
selves the ariiculafions are found to differ. In I\Ian, tho radius of the fore-arm is con- 
nected by a ball and .socket-joint with the hum(?i us, at its one extremity, and it rotates 
'ipon the other. But in tlie Uodentia, and many Paehydermata, the radius is con- 
**ected by a hinge-joint with tho humerus, and is immoveable at its other extremity. 
In some species those bones are even completely united. 
The second class of articulation (Synarthrosis) admits of no motion whatever; it 
W said to form a suture when two flat bones join each other by the edges; to be squa~ 
when the thin edge of the ono bone covers that of the other; dcniiculary when 
the edges are notched and indented together; and harmonic^ when they simply touch 
each other. We find, in the bones of the face and bead of Man, instances of these 
^fferent kinds of aiticulation. Tho manner in which tho bones of tho skulls belong- 
to the several Mammalia are joined together, bears a great resemblance to that 
•observable in Man; and wc find, in all, that they have a tendency to ossify as their 
ages increase. A variety of this kind of articulation is found in the teeth of JIan 
and Quadrupeds. These are inserted like wedges into the cavities of other bones. 
I’o this style of connexion the name of Gomphosis has been assigned. 
There is no instance found in the human skeleton corresponding to that singular 
^‘^d of articuliitiuu observed in tho nails of the Cats. These are inserted into small 
cavities in tho last phalanges of tho iocs, and at the same time they receive a pivot, or 
aniinence of the phalanx, into a small cavity of tlieir own, prepared to receive it. This 
^’irious contrivance is also found in otlicr quadrupeds with powerful (flaws. We also 
^**d it ill the tu^k of the Morse, where a small pivot is observed to project from the 
of tho ulvculi. 
"Iho third kind of articulation (Jmphiarthrosis) admits only of a slight and rc- 
'fricted motion. This is not occasioned by the form of the bones, which arc perhaps 
perfectly adapted for free motion, but by the cartilages and ligaments which are placed 
between tin; hones forming the articulations, and uniting firmly with them. The ver- 
'ebrui of tlie back exhibit this restricted motion ; but the bones of the pelvis arc 
Joined in such a miumcr as scarcely to permit any motion whatever, 'i’he bones of 
W’risl and instep ore considered, by some anatomists, to belong to this class; for, 
^*»«gh they appear to be provided with a few smooth articulated surfaces, yet they 
confined so greatly by the surrounding ligaments, that they move upon each other 
'''^ith great difficulty and through a very narrow space. 
In the second and third kinds of articulation, the edges or surfaces of tho bones 
either come immediately into contact, or else they are hound together by a substance 
which attaches itself throughout their entire parts of connexion. Also, the perios- 
teum is continued from one bone to the other, and is more intimately connected at 
the place of their junction than at any other part. In this respect they differ wholly 
from the kind first described. 
The muscles which set these bones into motion are as various as the movements 
destined to be performed. Those composing the trunk of tho Elephant are unrivalled 
for the union of strength, variety, and delicacy. As the snout of most animals is 
incapable of performing any considerable motion, we are naturally struck with asto- 
nishment at seeing an organ, which appears at first sight to be merely a prolongation 
of the snout, performing all the offices of the human hand. This delicacy is owing 
to tho immense number of minute muscles which are arranged in various directions, 
and thus enable the animal to execute the various movements of the organ. Upon mail- 
ing a transverse section of the proboscis, counting the number of short muscles, and 
then allowing the breadth of a line for the succeeding ones, which is considerably 
more than their thickness, some estimate may be formed of the number of muscles 
composing the trunk of the Elephant; and, upon adding these to the number of 
bundles comprising the horizontal layers, they are found to amount to between thirty 
and forty thousand. The snout of the Tapir is formed on a similar principle, with an 
additional muscle, corresponding to that which raises the upper lip of the horse. 
In Monkeys, the muscle w'hich frowns (^c.orTvyutor supercilii') is large, and is fre- 
quently used, but without expressing tho feelings indicated by that action in Man. In 
most quadrupeds the muscles, moving the external car, are more strongly developed 
than in Man. They arc thus enabled to give a great variety of attitudes to that organ, 
which enables them to collect sounds in every direction. Most quadrupeds, after an 
agreeable sensation, will erect their cars, and depress them when displeased, in the 
same manner as the Horse is in the habit of doing. Those animals which possess the 
pow’er of rolling themselves up, as the Hedgehog, have a number of curious muscles 
for that purpose. The muscles of tho tail are generally strongly developed; especially 
in the Kangaroos, which use them for standing and leaping, and in the Monkeys hav- 
ing prehensile tails. 
A certain degree of similarity prevails between tho muscles of Man and those of 
all the other Mammalia; but this resemblance is, upon the whole, greatest between 
Man and tho Quadrumana. But we cannot fail to remark tho small development in 
the calf of the leg, and in the buttock, among the Apes, as these muscles arc inti- 
mately connected with tho upright posture peculiar to Man, and the beauty of the 
human form. Many muscles, however, are found exclusively in Quadrupeds. Thus 
the fleshy panniclc (pannicuhis cnrnostts)y that sub-cutaneous covering of the body, 
is of very great size in the Hedgehog, Armadillo, Porcupine, and all animals possess- 
ing the power of rolling themselves up. This cutaneous expansion is even found in 
tho Cetaceous tribes; and the inhabitants of the Aluntnm Islands are said to fabricate 
a thread of great delicacy from the tendinous fibres of this muscle, procured from the 
Whale. 
Certain muscles arc distinguished for their very great strength. Tims the Horse 
is enabled to kick backwards with very great force, owing to the great development 
of the Gluteus medius and Gemellus muscles. 'Ihe Mole is enabled to burrow under 
ground, and to throw up the earth, by tho great magnitude of the pectoralis majory 
hitissimus dorsiy and teres major muscles. 
There is also a curious arrangement In the muscles belonging to the epiglottis of 
the several Mammalia. In the motion by which we elevate and depress the hyoid 
bone and the larynx, tho muscles acting on the bones, ami other hard parts, may be 
Compared to ropes drawing a resisting object in a certain direction. Innumerable 
muscles of a complicated form may bo seen in the tails of these ApUvS having that 
organ prehensile. It is said that no less than two hundred and eighty muscles were 
discovered by Mery in the prehensile tail of a Corcopithecus. 
Although the manner in which the bones arc artieulatefl determines the motions 
which they arc capable of performing, yet if is by the nunibor and direction of the 
imwclcs attached to the bones that the motions performed by each b(jnu are fixed. 
The muscles are attached to tho hones by tendons. Tho fibres of which the ten- 
don is composed are of a closer and denser texture than those of the muscles, and of 
a silvery whiteness. B(;ing penetrated by fewer vessels and no nerves, its substance 
seems altogether gelatinous. It possesses neither irritability nor sensibility, aiul forms 
tho passive link, by means of which the muscle acts upon the bone. Portions of 
teudou are found both inside and on the surface of several muscles ; and even those 
tendons, by which the muscles are inserted to the bones, penetrate a certain length 
into their fleshy substance, where they are interlaced in various manners. The term 
aponeurosis has been applied to those tendons which are broad and thin. 'J'he ten- 
dons have a great affinity for pliospbate of lime, which they often absorb with facility 
when their action is frequently repeated, and when employed to execute violent mo- 
tions. This frequently occurs with the Jerboas and other animals, which constantly 
leap witli their hinder limbs. It is considered probable that all the elementary muscles 
exercise an equal force at the moment of their contraction; but the degree of force 
with which a musclo can b© exercised greatly depends upon the manner in which its 
fibres are disposed, and the situation of the muscle itself, in respect to the bone or 
part it has to move. We therefore cannot estimate the force of a muscle by its mass, 
or by the number of fibres of which it is composed, but must also consider the com- 
position of the muscle and the method of its insertion. 
Tho muscles are cither simple or compound. In tho simple muscles all the fibres 
have the same disposition. The most usual are the ventriformy having all the fibres 
nctirly parallel, and forming a long bundle of a round form. The fleshy parts swell in the 
middle, forming the belly of the muscle, and becoming smaller at each extremity, 
where they terminate in tendons. Another kind of simple muscle consists of those 
that arc flat, and have parallel fibres, forming a sort of fleshy membrane, which is 
terminated by aponeuroses or tendinous membranes, instead of ending in small ten- 
dons. Both these kinds sometimes have ttmdons or aponeuroses in their middle, or 
in other points of their bodies. It is obvious that, in cither, the total action of tho 
muscle is equal to the sum of all the particular actions of the fibres; and that, if tho 
