Why are certain animals called vertebrated?

Because they have a cranium, or bony cavity, containing the brain, and a succession of bones called the spine, and the divisions of it vertebræ, proceeding from the cranium, and containing a prolongation of the brain, denominated the spinal marrow. Why are other animals called invertebrated? Because they have no vertebræ.

Why does the faculty of instinct differ from intelligence?

Because instinct makes animals perform certain actions, necessary to the preservation of the species, but often altogether foreign to the apparent wants of the individual; and often, also, extremely complicated. We cannot attribute these actions to intelligence, without supposing a degree of foresight and understanding infinitely superior to what we can admit in the species that perform them. The actions performed by instinct are not the effects of imitation, for the individuals that execute them, have often never seen them done by others; they bear no proportion to the common intelligence of the species, but become more singular, more skilful, more disinterested, in proportion as the animals belong to the less elevated classes, and are, in other respects, most stupid. They are so much the property of the species, that all the individuals perform them in the same manner, without any improvement.

The working bees have, since the beginning of the world, constructed the most ingenious edifices, agreeable to principles of the highest geometry, and destined to lodge and nourish a posterity which is not even their own. Solitary bees and wasps form also very complicated nests for their eggs. From the egg there springs out a worm, which has never seen its mother, which does not know the structure of the prison in which it is enclosed; but, when once it is changed into a wasp or bee, it constructs a similar nest, equally perfect, for its own egg,

BONES.

Why is fossil osteology, or the knowledge of bones dug out of the earth, an important branch of anatomy?

Because it not only brings to our knowledge races of animals, very different from those with which we are acquainted, but supplies many intermediate links, in the gradation of structure, which are wanting in the present creation ; and, therefore, makes it probable that, when the two are sufficiently investigated, one regular, connected chain will be formed, each class of animals imperceptibly running into that which is next to it. - Sir E. Home.

Why are bones excellent manure?

Because of the large proportion of lime which they contain.

Why are teeth important in identifying different animals?

Because, by the largeness of the tooth, the naturalist can judge of the relative size of the animal which bore it; and by the form of the tooth he can tell whether it was fitted to grind grass, or to tear flesh; and therefore, whether it belonged to an herbivorous or a carnivorous species. Pursuing his enquiries from this point, he could decide in a great degree, as to the structure of the stomach and viscera; the extremities, whether armed with claws or protected with hoofs; and, farther, he can judge of the vivacity of the senses which belonged to the animal, and of the habits which it derived from its peculiar conformation:-knowing, beyond all doubt, that there was an intimate agreement in all the properties of its existence, and that every thing in its organization was regulated by an undeviating harmony. Lib. Ent. Knowledge.

Why are the lives of wild animals shortened by the loss of teeth?

Because, as old age increases, the teeth fall out,

and the means of

body sinks to rest.

obtaining food thus failing, the 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 animals always sharp?

Because, as the teeth are covered by enamel only on their anterior 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 gum: 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 œsophagus 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 esophagus; 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 œsophagus 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 animal 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 in 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 has 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?