The sense of smell is very acute in the E., as is also that of hearing. The ears are large and pendulous; the eyes are small.
Elephants have no canine teeth, nor have they any incisors in the lower jaw. The upper jaw is furnished with two incisors, which assume the peculiar character of tusks, and attain an enormous size, a single tusk sometimes weighing 150 or even 300 pounds. The tusks are, however, often imperfectly developed, 10 or 12 in. in length, and 1 or 2 in diameter. These stunted tusks are often used for such purposes as snapping off small branches and tearing climbing plants from trees. Those elephants which possess great tusks employ them also for such other uses as loosening the roots of trees which they cannot otherwise tear from the ground; or in a state of domestication, for such labors as moving great stones, and piling or carrying timber. A powerful E. will raise and carry on his tusks a log of half a ton weight or more. The tusks of the E. surpass in size all other teeth of existing animals, and are the largest of all teeth in proportion to the size of the body. They consist chiefly of that variety of dentine called ivory (q. v.), and continue to grow—like the incisors of the rodents, to which they are in some respects analogous—even when the animal has attained a great age, if not to the very end of its life. The young E. is at first furnished with deciduous incisors, which are shed between the first and second year, and are succeeded by the permanent tusks.— The molar teeth of the E. are developed in succession; and at least in the Indian E., never more than two are to be seen in the same side of a jaw at one time. The first molars cut the gum in about two weeks after birth, and are shed about the end of its second year. The sixth molars, which are also believed to be the last, are supposed to appear about the fiftieth year of the E.'s life. The molar teeth of the E. are remark able for their great size, and for the extreme complexity of their structure, to which the nearest resemblance is found in some of the srhall rodents. They are composed of vertical plates of bony substance, separately enveloped in enamel, and cemented together by a third substance, called erusta petrosa, cortical, or cement, more resem bling bone than enamel. Each succeeding tooth is not only more complex, but occupies
a greater space in the jaw than its predecessor. Although formed from a single pulp, the molar tooth of an E. resembles an 'aggregation of teeth; and in the earlier stages of its growth, when the cement is not yet deposited, it seems as if many separate teeth were soldered together. As the surface of the tooth is worn down by mastication, the harder enamel is exposed in elevated ridges. The whole of a tooth is not in employ ment at once. From the peculiar manner of its growth, the anterior part begins to be employed, and to be worn away, whilst the latter part is still in process of formation.
The digestive apparatus of the E. is similar to that of the other pachydermata; but the stomach, which is of a very lengthened and narrow form, exhibits a peculiarity which assimilates it to that of the camel; the internal membrane, at the extremity beyond the cardiac orifice, forming thick wrinkles and folds, the broadest of which, and nearest to the gullet, seems to act as a valve, making that end of the stomach a reser voir for water, capable of containing about ten gallons; whilst a peculiar muscle, connecting the windpipe and gullet, enables the animal to open this reservoir at pleasure, for the regurgitation of the fluid, which is then sometimes received into the trunk, and squirted over the body, to free it from the nuisance of flies or the heat of a tropical sun.
The female E. has only two teats, situated between the fore-legs. The young suck with the mouth, and not with the trunk. They are suckled for about two years. The period of gestation is also nearly two years, and a single young one is produced at a birth.
The skin of the E. is very thick, of a dark-brown color, and in the existing species. has scarcely any covering of hair. The tail 'does not reach to the ground, and has a. tuft of coarse bristles at the eud. The feet have in the skeleton five distinct toes, but. these are so surrounded with a firm horny skin that only the nails are visible externally, as on the margin of a kind of hoof. The foot of the E. is admirably adapted for steep. and rough ground, the protective skin which covers the toes allowing them considerable freedom of motion.