70 



FIRST CLASS OF THE VERTEBRATED ANIMALS. 



formed, there may be seen, at the surface of the intestinal membrane, small eminences 

 like spongioles, which appear to erect themselves, and become filled with the fluid. 

 On compressing these spongiolcs or small 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 

 pi)int 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 i>umped 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, that tlie chyle penetrates into the lymphatic vessels 

 of the 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 

 ill the lungs. We may peiceive many points of resemblance between the chyle and 

 blood, in the spontaneous separation of their parts, in the fibrins which they both 

 contain, and in their being snnllarly affected by oxygen, which colours them both 

 red ; and we are 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 chai'acters 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 well 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 animalized, finds its 

 way into all the organs of the body, which it renovates and repairs. Thus, an iden- 

 tification of new 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 dimension, 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 th?y 

 are composed is incessantly dissipated in various ways, such as by respiration, perspi- 

 ration, friction, and many others. These losses in the human frame amount to as 

 much as several pounds weight of substance in the course of the twenty-four hours. 

 Without an adequate supply of nutriment, the strength of the animal soon becomes 

 reduced, its bulk diminished, and it finally perishes. There 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 hitherto ascertained, relative to the obscure function of 

 Nutrition. The necessity for a supply 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 diflterent 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 and seasons. On the other hand, old age, 

 prolon2;cd 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 declines the in\'itation 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 Spider?, 

 aU which animals can remain a very long time without food, and do not appear to 

 suffer from their continued abstinence. On this account they are in. general of a 

 more meagre habit of body than such animals as live either on herbs or fruits. 

 There are many instances on record of old JMen, 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 difQeult to prove, in this 

 case, that the 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 neai-ly 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 

 frequently tormented with a devouring hunger. Next to Sleep, which wholly sup- 

 presses this appetite for the time, nothing tends more to drive away Hunger than the 

 long-continued exercise of deep thought. 



This appetite for food, which i\Ian is enabled to confine within the bounds of 

 Reason and Temperance, becomes in the lower animals one of the leading principles of 

 action. Indeed, if we 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. To obtain a 

 sufficient supply of nourishment, is the great end, to which a large proportion of 

 the instincts of each animal bear an immediate reference ; and we commonly find, 

 that those animals which possess the greatest facility in obtaining a subsistence, have 

 the greater number of enemies to avoid. Such instincts as lead immediately to self- 

 preservation from external danger, are more developed in the Herbivorous animals, 

 than these other kind of instincts which relate more especially to their maintenance; 

 and it is among the Carnivorous animals, whose existence depends solely upon tliGir 

 skilful exertions, that we find the mobt ingenious devices to deceive and destroy 

 their prey. 



The Quadrumana, especially the Monkeys, find an easy maintenance m the fruits of 

 those warm countries, where alone they have fixed their abodes. Secure on the tops 

 of trees, they have few other enemies to avoid than the Serpent tribes, which infest 

 the lower branches. If we except those mai-auding parties, which thay ai'e 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 Roussctte 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 hang securely suspended by their thumb-nails to the roofs of 

 caverns, and other obscure retreats. The Galeopitheci, 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 the lower branches. 



The Insectivora, 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 f or Aquatic Shrew, add to their subterranean habits a mode of life 

 almost subaqueous. 



The Plantigrada, though omnivorous, differ in their tastes ; some, as the Bears, 

 are paitial to a vegetable diet, while others, like the Glutton ( Gido arcticus)^ prefer 

 animal food. The latter devours enormous quantities of fleth, and when urged bv 

 famine, conceals itself among the lower branches of a tree, Irom 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 are compelled, by the sagacity of their prey, and 

 their more exclusive propensity for animal food, to resort to many inf^enious devices 

 for obtaining it. With the greater number of these animals, the principle of destruc- 

 tion is so strong, that they will destroy every living animal wMthin their reach, al- 

 though their hunger may be completely satisfied, so well are they disposed to execute 

 the olBce of Nature's executioners, in curbing the excessive fecundity of the smaller 

 tribes. Animals of the Gonus Felis, such as the Lion, Tiger, and Leopard, never 

 attempt to run down their prey by swiftness. Their sense of smell beino- somewhat 

 obtuse, they rather seek to conceal themselves in a thicket near those places where 

 the herbivorous animals come to drink, and spring upon their prey by one, or at most 

 two or three bounds. If unsuccessful, which seldom happens, they retieat to their 

 covert, or remove to a more favorable spot. On the other hand, the Genus Canis 

 such as the Jackal and Wolf, are skilful in tracking their game, which they run 

 down by perseverance, or overcome by force of numbers. These animals, with the 

 Hysna, do not refuse carcasses, though in the last stage of decay, and disinter hu- 

 man bodies from the sands of the African deserts, or the cometeries of the East. The 

 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. The *' Jackals' shriek," which is re-echoed by the distant 

 hills, their voracity, aud 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 

 caravans. At their frightful clamour, the Antelope and other herbivorous animals 

 are roused from their coverts, and take to flight, when they fall, perhaps, into the 

 ambuscade of some Lion or Leopard, while the band of Adives witness the success 

 of this other brigand with jealous eyes, and ai'e left only to dispute the mann-led re- 

 mains of the feast. 



The Amphibia feed chiefly on fish, which they always devour in the water; thou'^h 

 some species seem capable of living occasionally on Fuel. 



Those instincts of the Rodentia which refer to their self-preservation from ex- 

 ternal danger, are more remarkable than any others. No animals are so skilful in 

 forming subterranean retreats, which are usually executed by the combined labour of 

 an entire settlement. One individual props up the earth which threatens to fall, 

 another divides a large cavity into apartments, and a third forms a water-proof roof, 

 with a layer of clay, to preserve the entire dwelling from the rain. One apartment 

 is destined for the nursery, another for the granary. Here these animals amass, dur- 

 ing the latter part of the autumn, a plentiful supply of provisions, ai-.d they find, on 

 waking in the spring from th^ir long winter sleep, that maintenance which would 

 otherwise have completely failed them, until the returning autumnal fruits and grains 

 again permitted them to amass another hoard. The Squirrels accumulate hazel-nuts, 

 or the cones of the pine ; the Dormouse gathers acorns and kernels ; the Marmot 

 seeks for different roots ; and many species of Rats select bulbous roots in particular. 

 Other species penetrate into our granaries and stoiehouses, composing a kind of ver- 

 min, which nothing can entirely extn-pate. 



Among the Edentata, the Tardigrada or Sloths feed chiefly on the leaves of trees, 

 while the proper Edentata, such as the Armadillo, prefer insects and carcasses, thoufrh 

 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 fast 

 without inconvenience, and it never drinks, being supplied only with Vegetable 

 fluids. Prevented by its singular organization from any rapid movement, the Sloth 

 devours every soft pait of the tree within its reach, commencing with the leaves, and 

 following on with the buds, tender shoots, and bark, until the whole tree is left en- 

 tirely bare. Here the animal remains motionless and without eating for many days, 

 until extreme hunger finally compels it to seek for food. Rolling itself in a ball, and 

 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-hills 

 of South America, and the larger species frequent the neighbourhood of bui*ying- 

 grounds in great numbers. By means of subterraneous excavations, they invade the 

 graves of the inhabitants, unless carefully protected by boards from their incursions. 

 The three tribes of Mai'supialia present a groat variety in their tastes for food. 

 Among the Dide^phida we find a strong partiality for animal food of every kind, yet 



