70 
FIRST CLASS OF THE VERTEBRATED ANIMALS. 
formed, there may he seen, at the lurface of the intestinal membrane, small eminences 
like spongiolcs, which appear to erect themselves, and become filled with the fluid. 
On compressing these spongioles or sm::U projections, the chyle exudes ; and when 
they are examined with the microscope, we may perceive them to be ramified with 
innumerable small vessels, and their surfaces perforated with minute pores like the 
point of a needle. These pores are conjectured to be the commencement of the 
white vessels or lacteals, which carry off the chyle, and that by their means the chyle 
is gradually pumped out or absorbed at the surface of the intestine. We are entirely 
ignorant of the nature of that power by which this absorption is effected, but it has 
been ascertained from experiment, tliat the chyle penetrates into the lymphatic vessels 
of tlie intestine, and traverses the glands of the mesentery ; that it is conveyed by 
proper vessels to the thoracic duct, through which it is finally carried into the blood. 
Once united to the blood, the chyle experiences the propelling force of the heart, 
traverses the organs of respiration, and comes in contact with the air always existing 
in the lungs. We may perceive many points of resemblance between the chyle and 
blood, in the spontaneous separation of their parts, in the fibrine which they both 
contain, and in their being similarly affected by oxygen, which colours them both 
red ; and wc ore fully entitled to conclude that this fluid, arising from the digested 
aliments, is actually changed into blood during its passage through the organs of 
respiration, for on leaving the lungs, the chyle has lost all those characters which 
formerly distinguished it from blood. 
As the blood is continually undergoing waste in its contributions towards the for- 
mation of the several secretions, as vtell as the reparation of the organs, this loss must 
be supplied by the aliment, without which life soon becomes extinct. The digested 
product of the food being altered in its properties, and completely animaliaed, finds its 
way into all the organs of the body, which it renovates and repairs. Thus, an iden- 
tification of now matter with the former substance of the animal body is finally 
effected, and this process constitutes the essential part of the function of nutrition. 
All portions of the animal frame undergo continual changes of dimemion, form, and 
structure, from the first period of their formation, until the body is finally subjected 
to the ordinary laws of inanimate substances. A part of the elements of which they 
are composed is incessantly dissipated in various ways, such as by respiration, perspi- 
ration, friction, and many others. Tliese losses in tho human frame amount to as 
much as several pounds weight of substance in the course of the twenty-four hours. 
M'ithout an adequate supply of nutriment, the strength of the animal soon becomes 
reduced, its bulk diminished, and it finally perishes. TUcre appears to exist a con- 
stant internal action, by which all the organs appear to be continually worn away and 
destroyed, only again to repair themselves, when supplied, through the food, with the 
proper elements for their composition. 
Such are the leading facts hitlierto ascertained, relative to tho obscure function of 
Nutrition. The necessity for a snpply of food is felt by all animals, yet it is not ex- 
perienced in an equal degree by all species, nor by animals of the same species, nor 
even by the same animal when placed in different circumstances. This appetite for 
food is heightened by youth, fatigue, long-continued want of sleep, by violent passions 
when the paroxysm has passed, by convalescence after a long illness, by a dry and 
cold air, and the influence of climates aud seasons. On the other liand, old age, 
prolonged sleep, hybernation, perfect repose, and hot baths, diminish the necessity for 
food. With the human species, luxurious habits lead to a loss of appetite, while it 
is heightened by labour ; and thus Hunger, which dcclioes tho invitation of the opulent 
epicure, comes an unwelcome guest into the hovels of the destitute. 
In general, the carnivorous .animals endure a long-continued fast with less incon- 
venience than the herbivorous. This remark must not be confined to the Mammalia, 
for it extends to the Birds of Prey, especially to the Eagle, to Serpents, and Spiders, 
all which animals can remain a very long time without food, and do not appe-or to 
suffer from their continued abstinence. On tins account they ai-e in general of a 
more meagre habit of body than such animals as live either on herbs or fiuits. 
There arc many instances on record of old Mon, but more especially of Women, who 
have lived for several weeks, some say months, without food. A mad enthusiast who 
imagined himself to be Christ in person, remained, it is said, during the forty days of 
Lent without using any food whatever ; but confined himself, without swallowing any 
thing, merely to washing his mouth with water or wine. These instances are not, 
however, always very well authenticated; and it would be difficult to prove, in this 
case, that tho fanatic did not actually swallow some of the fluid. Moisture, dark- 
ness, and repose, tend to diminish the usual effects of abstinence. A dog has remained 
alive under these circumstances for nearly fifty days without food. Persons of a 
vivid imagination, as well as frantic madmen, have in general a digestion extremely 
energetic, and they sometimes consume enormous quantities of food. Idiots also are 
freijuently tormented with a devouring hunger. Next to Sleep, which wholly sup- 
presses this appetite for the time, nothing tends more to drive away Hunger Hum tho 
long-continued exercise of deep thought. 
This appetite for food, which Man is enabled to confine within the bounds of 
Peason and Temperance, becomes in tho lower animals one of the leading principles of 
action. Indeed, if wc except the reproductive principle, and the principle of self- 
preservation from external danger, there are no others which approach in violence 
to the appetite for food, especially when heightened by abstinence. H'o obtain a 
sufficient supply of nourishment, is tho great end, to which a largo proportion of 
the instincts of each animal bear au immediate reference ; and wc commonly find, 
that those animals which posacss tho greatest facility in obtaining a subsistence, have 
the greater number of enemies to avoid. Such instincts as lead imineiliately to self- 
preservation from external danger, ore more developed in tho Herbivorous animals, 
than those other kind of instincts which relate more especially to their maintenance; 
and it is among the Carnivorous animals, whose existence depends solely upon their 
skilful exertions, that wo find the most ingenious devices to deceive and destroy 
their prey. 
The (iuadrumana, ospocialiy the IMonkeys, find an easy maintenance m the fruits of 
those warm countries, whore alone they have fixed their abodes. Secure on the tops 
of trees, they have few other eneraies to avoid than the Serpent tribes, which infest 
the lower branches. If wc except those marauding parties, which they aic sometimes 
compelled to form, in a great measure they are relieved from the cares which ha*- 
rass most other animals. But the Lemurs, being chiefly nocturnal, prey upon the 
small Birds and Insects while sleeping upon the branches. The Loris, favored 
by the darkness, steals upon its reposing victim, with a step so noiseless and 
excessively slow, that it is enabled to secure its prey with as much certainty as 
those Carnivora which depend for subsistence upon the extreme rapidity of their 
movements. 
Some of the Cheiroptera, such as the Roussetto Bats, feed almost wholly on fruits ; 
the remainder pursue the Moths and Gnats which fly about during the summer 
evenings. A few in South America venture to suck the blood of Man, and of the 
larger quadrupeds, but their bites are neither deep nor dangerous. During the day, 
and in winter, they bang securely suspended by their thumb-nails to the roofs otf 
caverns, and other obscure retreats. The Oaleopithcci, or Flying Cats, by means of 
their membranes, extended like a parachute, dart from the tops of trees, by para- 
bolic leaps, upon the small birds reposing on tho lower branches. 
Tiie liisectivora, as their name denotes, feed chiefly on Insects ; to these they add 
Worms, Snails, and tender roots. Some of these animals, such as the Mole, seek 
out their prey beneath the surface, by long mining operations; others, as the Sea- 
lops Canadensis, or Aquatic Shrew', add to their subterranean habits a mode of life 
almost subaqueous. 
Tho Planligrada, though omnivorous, differ in their tastes : some, as the Bears, 
arc partial to a vegetable diet, while others, like the Glutton (^Gulo arcticus)^ prefer 
animal food. The latter devours enormous quantities of flesh, and when urged by 
famine, conceals itself among the lower branches of a free, from which it watches 
for an opportunity to leap upon the back of some quadruped passing beneath, whose 
blood it continues to suck, until exhaustion compels the larger animal to yield to its 
more cunning enemy. 
The numeious genera of Carnivora arc compelled, by tho sagacity of their prey, and 
tlieir more exclusive propensity for animal food, to resort to many ingenious <levices 
for obtaining it. With the greater number of these animals, the principle of destruc- 
tion is so strong, that they will destroy every living auinial within their reach, al- 
though their hunger may be completely satisfied, so well are they disposed to execute 
the office of Nature’s executioners, in curbing the excessive fecundity of the smaller 
tribes. Animals of the Genus Fells, such as the Lion, Tiger, and Leopard, never 
attempt to run down their prey by swiftness. Their sense of smell being somewhat 
obtuse, they rather seek to conceal themselves in a thicket near those places where 
tho herbivorous animals come to drink, and spring upon thoir prey by one, or at most 
two or three bounds. If unsuccessful, wlucb seldom happens, they retieat to their 
covert, or remove to a more favorable spot. On the other band, the Genus Canis, 
such as the Jackal and Wolf, arc skilful in tracking their game, which they run 
down by perseverance, or overcome by force of numbers. These animals, with the 
Hyaena, do not refuse carcasses, though in the last stage of decay, and disinter hu- 
man bodies from the sands of the African desorts, or the cemeteries of tin* East. Tho 
Adives collect during the night, like bands of robbers, around the tents of the Moors 
or the Bedouin Arabs, who remain in momentary expectation of an attack from 
these ferocious brigands. Tho “ Jackals’ shriek,” which is re-echoed by the distant 
lulls, their voracity, and formidable numbers, strike the wanderer with terror ; and 
when once accustomed to human flesh, they cannot enjoy any other. They will as- 
semble at night to the number of two or three hundred, for the purpose of attacking 
ewavans. At their frightful clamour, the Antelope and other herbivorous animals 
arc roused from their coverts, and take to flight, when they fall, ]>crhdps, into the 
ambuscade of some Lion or Leopard, while the band of Adtves witness the success 
of this other brigand with jealous eyes, and are left only to dispute tho mangled re* 
mains of the feast. 
Tlie Amphibia feed cUiefly on fish, which they always devour in the water ; though 
some species seem capable of living occasionally on Fuci. 
Those instincts of the Rodentia which refer to their self-preservation from ex- 
ternal danger, are mure remarkable than any others. No animals are so skilful in 
foiming subterranean retreats, which are usually executed by the combined labour of 
on entire settlement. One individual props wp the earth which threatens to fall, 
another divides a large cavity into apaitnients, and a third forms a water-proof roof, 
with a layer of clay, to preserve tho entire dwelling froux. the rain. One a}>artmcut 
is destined for the nursery, another for the granary-. Hero these animals amass, dur- 
ing die latter part of the autumn, a plentiful supjjly ot provisions, ar.d they find, on 
waking in the spring from th«>ir long winter sleep, that niainlcnanco which would 
otherwise have completely failed them, until the returning autumnal fruits and grains 
again permitted them to ama.ss another hoard. The Squirrels accumulate hazel-nuts, 
or the cones of the pine; the Dormouse gathers acoins and kernels; the Marmot 
seeks for different roots ; and many species of Rats select bulbous roots in particular. 
Other species penetrate into our graiiaiies aud stutehouscs, con»posiug a kind of ver- 
min, which nothing can entirely extirpate. 
Among the Edentata, the Tardigrada or Sloths feed chiefly on the leaves of trees, 
while tho proper Edentata, such as the Armadillo, prefer insects and carcasses, though 
they all seem on an emergency to be likewise capable of digesting vegetable food. None 
of these animals ruminate. The Sloth is enabled to endure a long-continued f^i^^ 
without inconvenieuce, and it never drinks, being supplied only with Vegetable 
fluids. Prevented by its singulai* organization from any rapid movement, tho Sloth 
devours every soft pai't of the tree within its reach, commencing with the loaves, 
following on with the buds, tender shoots, and bark, until the whole tree is left 
tirely bare. Here the animal lemains motionless and without eating for many day^» 
until extreme hunger finally compels it to sock fur food. Rolling itself in a ball, 
falling heavily from the branches upon the ground, it crawls with measured pace to 
the nearest tree. The Armadillo burrows under ground into the numerous Ant-hiU* 
of South America, and thu larger species fiequent the ucighbuurhood of burymg' 
grounds in great numbers. By means of subLerraneons excavations, they invade the 
graves of the inhabitants, unless carefully iirotected by boards from their incursionS- 
Thc three tribes of Slarsupialia present a great variety in their tastes for 
Among the Didolphida we find a strong partiality for animal food of every kind, 
