THE ORGAN'S OF ANIMAL BODIES— THEIR FUNCTIONS. 
9 
placed forwards, to aid in discovering their prey. Animals, though seldom susceptible 
of musical notes, sometimes exhibit an aversion for the low or grave sounds. This is 
rcmai’kably the case with the lion. In bats, the sense of hearing is surprisingly acute. 
L’organe de la generation est douS d’un sixieme sens, qui est dans sa 
peau intcrieure. 
Perhaps a greater claim to the right of being termed the sixth semse, may be estab- 
lished in favor of that feeling of resi.stance, or muscxtlar sense, by which we perceive 
the degree of force exorcised by particular muscles. The mouth and lips of a new- 
born animal are directed by this sense to their proper function ; and the adult would 
be in danger of a fall while engaged in wNalking, leaping, or other active exercises, if 
he were for a moment unconscious of the present state of the muscles appropriated to 
those actions. Shooting, bounding, and taking aim, presuppose a conaciou.sncss of 
the degree of mu.seular exertion sulhcient to produce a certain effect; and instances 
are not wanting of its sur})ri<ing accuracy. Thus, the Indian fresh water fish called 
tho Chfr-tudon roslralvs, will hit an insect with a small drop of water at a distance of 
several feet, and the oncutnberetl inw^it speedily falls an easy prey. When the ele- 
phant is annoyed by flics, he will discharge a large quantity of water upon tho part 
attacked, with sufiiciont accuracy and force to dislodge them. Tho deadly spring of 
the lion and tiger cxhibitji the instantaneous result of the muscular sense in its most 
tremendous form. Dr Ycliowley mentions tho case of a woman who was afliicted 
with tlic disea'^c called antesthesia^ where the muscular sense of her hands was lost, 
although the muficular power remnined. On turning her eyes aside, she used to drop 
glasses, plates, &c., which wore held in safety as long as another sense supplied the 
place of the lost one. 
The stomacli and intestines are possessed of certain peculiar sensations 
wiiicli declare the state of these viscera; and indeed every part of tlie 
l)ody is susceptible of sensations, more or less painful, when affected by 
accident or disease. 
Pain teaches an animal to avoid hurtful objects, and is wisely given as a safeguard 
to his frame : accordingly, its seat is mostly at the surface. The deep parts of tho 
body have but little sensation, as it would there be only a useless encumbrance. Tho 
animal is continually warned, by uneasy sensations, to change his posture frequently, 
to avoid high degrees of heat, and, in general, to accommodate his frame to surround- 
ing circumstances. 
Many animals are defective both as to ears and nostrils, several are 
destitute of eyes, and some are reduced solely to the sense of touch, which 
is never wanting. 
In the higher animals, impressions made upon the external organs of 
sense are.transniitted by the nerves to the brain and spinal marrow, which 
form tho central masses of tho nervous system. The elevation of an ani- 
mal in the scale of creation may [frequently] be determined by tho volume 
of its brain, and the degree in which the power of sen.sation is concen- 
trated there. Animals of a lower grade have the medullary masses much 
dispersed ; and in the more simple genera, all trace of nerves seems to be 
lost in the general substance of the body. That part which contains the 
brain and principal organs of sense is called the head. 
We now proceed to consider the second animal function — namely voluntary 
Motion. 
hcii the animal wills to move, in consequence of a sensation upon 
an external organ, or any other cause, the motion is transmitted to tho 
muscles by means of the nerve.s. 
This power of originating motion, residing in the nervous system of living .animals, 
's one of the most womlcrfiil properties of Iheir nature. Every machine, however 
comjjlicateil or varied in its structure, can only be set in motion by some external 
P'Jwer already e.xistlug in nature, or produced by art, whether it be the expansive 
turce of steam, the descent of weights, the action of running water, or the recoil of 
^ spring. No perpetual motion can ever be preserved by any arrangement of the 
parts of a machine among themKclves; they must rest ultimately upon a prime mover, 
^ut the exquisite arrangement of the animal frame aurpa-sses, in this respect, the 
highest mechanical skill. The mind wills — tlie muscle contracts. How much so- 
ever we may desire to unravel the mystery, tho process is inexplicable, and seems 
for over removed beyond tho reach of human ingenuity. The only fact hitherto as- 
'•ertainod Is-, that if the nerve bo separated, seriously injured, or even tightly com- 
pressed, the motion of the mu-selc will not follow the volition of tho mind. 
The miLsclos are bundles of fleshy fibres, by tho contraction of which 
‘he animal body performs all its motions. The extension and lengtheu- 
'f'g of the limbs arc equally the result of muscular contraction with their 
bending and drawing in. They are arranged in number and in direction 
‘o suit the motions which cacli animal is destined to perform ; and when 
“ becomes necessary to execute these motions with vigour, tho muscles 
'‘fe inserted upon hai-d parts, which are so articulated, one over the other, 
to constitute them so many levers. These parts, in the vertebrated 
'toinials, are called hones. They are situate internally, and are formed of 
•t gelatinous mass [of cellular substance, the pores of which are] pene- 
'i.ited by particles of phosphate of lime. In some of tho lower tribes of 
'■onmals, such as tho Mollusca, the Crustacea, and the Insects, these hard 
Patts are extenuil, and coitqiosed either of calcareous or of horny sub- 
st&nces, called shells, crusts, or scales, all of which are secreted between 
the skin, and the epidermis or cuticle. 
A considerable difference is found between the chemical composition of the bones 
belonging to the higher orders of animals and the external coverings of crustaceous 
animals. Human bones, when analyzed by Berzelius, were found to contain in 100 
parts nearly as follows: of animal matters, (being chiefly gelatine, cartilage, and mar- 
rovr) 34 parts; of phosphate of lime, 51 parts; of carbonate of lime, 11 parts; of 
fluate of lime, 2 parts; of phosphate of magnesia, 1 part; and of soda, muriate of 
soda and water, 1 part. Here the principal ingredient is phosphate of lime ; but in 
the hard parts of crustaceous animals, such as crabs and lobsters, the carbonate of 
lime is considerably in excess. The shells of the mollusca, such as muscles and oys- 
ters, are almost entirely formed of the carbonate of lime. On the contrary, the horny 
coverings of insects contain a very minute portion of earthy matter, and arc mostly 
composed of animal substances. The same proximate elements enter into the com- 
position of horns, nails, and hoofs, being gelatine, with a membranous substance, re- 
sembling the white of eggs boiled hard. The scales of fish arc composed of layers of 
membrane alternately with those of phosphate of lime, which arrangement is the cause 
of their brilliancy ; but the scales of serpents contain no phosphate of lime, and very 
much resemble, in their constitution, the horny coverings of insects. 
The fleshy fibres are inserted upon the hard parts, by means of other 
fibres of a gelatinous nature, called tendons, which seem to be a con- 
tinuation of the first. 
These tendons exercise the same office as straps or ropes in ordinary machinery, 
when it is required to transfer motion from one part to another. By this means a 
moving pow’cr can be exercised, in a spot where its immediate presence would be highly 
inconvenient. Thus, the hand is moved by tendons communicating with muscles, 
fixed at a considerable distance upon the arm ; and the velocity and delicacy of its 
movements arc not obstructed by their presence. Often these tendons are strapped 
down by cross cords, and pass along grooves in the bones, or through a pulley formed 
by a ligament. By these mechanical contrivances, the direction in w'hich the muscu- 
lar power a<‘ts may be changed; the forces of different muscles are compounded, and 
altered in intensity; and the velocity of the resulting motions modified according as 
circumstances may require. This arrangement also permits the accumulation of force 
upon one point; for a great number of muscular fibres arc employed to contract one 
tendon, in the same manner as several horses maybe employed to draw the same rope. 
The peculiar shape observable in the articulated surfaces of the hard 
parts confine the motions of the tendons within certain limits, and they 
are still further restrained by cords or envelopes, usually called ligaments, 
attached to tlie sides of the articulations. Animals become enabled to 
execute the innumerable motions involved in the exercise of walking or 
leaping, fljing or swimming, according as the bony and muscular appen- 
dages are adapted for these various motions ; and also, according to tho 
relative forms and proportions which the limbs, in consequence, bear 
among themselves. 
Nutrition, which we shall now explain, forms the first of the vegetative func- 
tions. • 
The muscular fibres connected with digestion and circulation are not 
influenced by tho will, but, on the contrary, a.s we have already explain- 
ed, their principal arrangements and subdivisions appear to be specially 
intended to render tlie animal completely unconscious of their exercise. 
It is only when the mind is disturbed by violent passions, or paroxysms, 
that its influence is extended beyond tlie ordinary limits, and that it agi- 
tates these functions common to vegetable life. Sometimes, when tho 
organs are diseased, their exercise is accompanied by sensation ; but, in 
ordinary cases, digestion and circulation are performed without tlie con- 
sciousness of the aninud. 
The aliment is first masticated, that is, minutely divided by the jaws 
and teeth, or sucked in, when taken by the animal in a liquid form. It is 
then swallowed entirely by the muscular action of the back parts of tho 
mouth and throat, and deposited in the first portions of the alimentary 
canal, which arc usually expanded into one or more stomachs, where the 
food is penetrated and dissolved by corrosive Juices. 
This gastrin juice pa8sosso.s the very remarkable property of dissolving most animal 
and vegetable matters, when deprived of life, and some mineral subshmees. It more 
especially acts upon such as yield nutriment to the animal, and are adapted to its gene- 
ral habits and formation. M bon recently procured from the stomai?h of a healthy animal, 
it appears as a clear mucilaginous fluid, slightly salt to the la-te. Substanees, when 
undergoing fermentation or putreliiction, arc immediately checked in their action by 
the gastric juice, and are formed by its corrosive influenee into a new fluid, possessed 
of entirely different properties, called chyme. But most mineral substances are indi- 
gestible. Certain tribes of savages, as tho Otomacs, will, however, swallow daily 
large quantities of earth to allay tho cravings of hunger. But this subst.Tnce does 
not appear to he dissolved; it merely acts mechanically in distending the stoniDch. 
The higher region of tho alhnunlary canal is occupied by llie stomach, which re- 
ceives the food conveyed to it through the (esophagus or gullet. The form .and 
siructuro of the stomach bears a constant relation to the nature of the food. In 
herbivorous animals, it is composed of a complicated system oi reservoirs, where, by a 
slow and intricate process, tho small quantity of nutriment contained in vc<>-ctable 
matter is abstracted and conveyed into the system. In carnivorous animals, the stomach 
