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and the means of obtaining food thus failing, the body sinks to rest. Man is the only animal that can counteract the fatal consequences of the loss of teeth.

Why are the incisor or front teeth of gnawing ani« mals always sharp ?

Because, as the teeth are covered by enamel only ou their apterior or convex surface, and the bone wears down much faster than this harder covering, the end of the tooth is a sharp cutting edge. No animal exhibits their structure better than the rat.

Why do carnivorous animals masticate their food very imperfectly?

Because their lower jaw can only move upwards and downwards, and is incapable of that horizontal motion which constitutes genuine mastication.

Why do other animals which live on vegetables, masticate their food thoroughly?

Because they can move the lower jaw backwards and forwards, and to either side, so as to produce a grinding effect, necessary to bruise grass and to pulverize grain. The teeth may be compared, in the carnivorous animals, to scissors : in the other animals, to the stones of a mill. - Blumenbach.

Why do carnivorous animals prey on those which derive their food from the vegetable kingdom ?

Because the food of all animals either mediately or directly, is derived from vegetables.

Why are the teeth of some animals, as the cow and sheep, darker in the centre than elsewhere?

Because the cement which should fill up the teeth, is sometimes not completely deposited before the tooth cuts the gun : hence, cavities are left in the centre of the tooth, which become filled with a dark substance, composed of the animal's food, &c. Blumenbach

Why are bullets sometimes found imbedded and concealed in ivory tusks ?

Because they have been lodged there by the muskets of hunters; and, as the tusks are continually growing during the animal's life, the bullet becomes surrounded by new layers of ivory, while no opening exists between it and the surface, to account for its entrance. - Philos. Trans.

Why does the dog, while changing his teeth, appear to have the canine teeth doubled ?

Because the permanent ones cut the gum before the old ones have fallen out.

THE STOMACH.

Why are certain animals called ruminating?

Because they first imperfectly chew and swallow their food, and subsequently return it through the csophagus or gullet, in small quantities at a time, to the mouth, there to be thoroughly masticated, and then swallowed a second time.

Why do certain animals ruminate ?

Because, it is supposed, of a voluntary power in the @sophagus; and, indeed, the influence of will throughout the whole process, is incontestible. It is not confined to any particular time, since the animal can delay it, when the paunch is quite full. Blumenbach knew four men who ruminated their vegetable food, and assured him they really enjoyed the process; and two of them had the power of doing, or abstaining from it at pleasure. The final purpose of rumination, is, however, unexplained. Blumenbach.

Why do some animals, as the dog, vomit very easily, while others, as the horse, scarcely can vomit?

Because of a peculiarity in the opening of the csophagus or gullet, into the stomach, both in size and mode of termination. Blumenbach.

Why are hair balls found in the stomachs of some animals ?

Because the animal has licked off its own hair, which thus gradually accumulated in the stomach.

Why is this hair found in balls ?

Because the motion of the paunch in which it is found is rotatory.

CLOTHING.

Why does the fur, wool, or feathers, of quadrupeds and birds, vary in quantity and quality, in different regions ?

Because, generally, of the temperature of the region which the avimal inhabits. Thus, the dogs of Guinea, the Indian sheep, and the African ostrich, are so thinly clothed, that they may be considered almost naked. The temperature of their bodies is thus necessarily diminished un proportion to the heat of the climate in which they live. The Iceland sheep and the Esquimaux dog, on the contrary, are covered with a warm coat both of hair and wool, which enables them to bear the most intense cold, without much inconvenience.

Why are the skins of hairs and rabbits seldom ripe in the fur till frosty weather hus set in ?

Because the growth of the hair is dependent upon the temperature of the atmosphere : previous to winter, the hair of all animals is increased in quantity and length, and the more they are exposed, the greater is the increase.

SECRETIONS.

Why have certain animals glands and bags secreting offensive substances ?

Because they may pour out the fetid matter when pursued; and thereby effectually defend themselves, as neither man nor animal can then approach them. This explains the smell of the polecat, the skunk, &c.

Why is the gall-bladder thought to belong particularly to carnivorous animals ?

Because it is connected with their habit of long fasting, and serves as a reservoir for the bile. Cuvier.

RESPIRATION.

Why do animals respire ?

Because their blood, white or red, hot or cold, must, in a state of health, be constantly supplied, either from the atmospheric air, or from water, with successive quantities of a substance necessary for the continuance of life (oxygen); giving off, in return, equal quantities of another, (carbon.) This remarkable process is principally effected by respiration, which red-blooded animals perform either by lungs, or, like fishes, by means of gills; and white-blooded, by analogous organs.

Why is respiration the principal cause of animal heat?

Because the air in breathing loses its oxygen, and is replaced by an equal quantity of carbonic acid gas, which is ejected from the lungs at a temperature of about 90°.

Why does the respiration of animals vary?

Because of the relative proportion of blood presented to the respiratory organs in a given time, and of the relative proportion of oxygen which enters into the composition of the fluid in which the animal lives, whether air or water.

In mammiferous quadrupeds the quantity of respiration is less than that of birds; but it is greater than that of reptiles, on account of the structure of the respiratory organs; and exceeds that of fishes, on account of the different elements in which they Jive. Hence result the four kinds of movements, which the four classes of vertebrated animals are particularly destined to exert. Mammiferous ani. mals, in which the quantity of respiration is moderate, are generally formed to develope their strength

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