Whilst the exposed part of the tooth is thus worn away, that part of the root which corre sporids with the portion gyound down is re moved by a very different process. NVhen examined under these circumstances, tbe roots of the anterior denticles have the appearance of being eaten away as by a kind of caries, so that all the front of the tooth is thus removed when the grinding surface has ceased to be efficient, and the tooth, when about to be shed, is reduced to a very small size, however large it might have been originally.
The tooth which is in use is therefore per petually moving forward in consequence of this process, and making room for that which is in progress of forrnation in the hinder part of the yaw to succeed it. This latter, in turn, by its development assists in pushing the first for wards, so that it is strictly true that in the Elephant the second set of teeth grows behind the milk set, instead of above or below them, as in other animals (fig. 479).
he direction of the single-fanged teeth of their patients by the application of wires.
Systeni.—The digestive apparatus is enormously developed in all the animals be longing to this order, being in this respect not only adapted to the quantity of materials con sumed for the support of their unwieldy bodies, but likewise in accordance with the strictly vegetable nature of the aliment upon which they feed, which, compared with animal sub stances, is necessarily bulky and innutritious. We select a few examples.
The stomach of the Elephant is simple, but in shape it is much more elongated than in the human subject. Its cardiac extremity is pro longed into a pouch of considerable size, the lining membrane of which is gathered into thirteen or fourteen large valvular folds, which, from their great size, seem to form so many broad valves. The muscular tunic of this pouch and around the cardia is remarkably thick, and its contents such as to indicate some analogy between this portion of the stomach and the abomasus or fourth stomach of rumina ting quadrupeds.
The small intestines are very voluminous, and the colon and ccecum of enormous dimen sions, presenting longitudinal tendinous bands and wide pouches as in the human subject. The following table will serve to shew the pro digious extent of the intestinal canal of an Elephant seventeen years of age, and only seven feet and a half in height.
ft. in.
Length of the small intestines from the pylorus to the mecum 38 0 Circumference of ditto 2 0 Length of ccecum 1 6 Circumference of ccecum 5 0 Circumference of colon 6 0 Length of colon and rectum to gether 20 0 Total length of intestinal canal, ex clusive of the ccecum 58 6 The liver requires no special notice, but the arrangement of the biliary ducts of the Ele phant is very remarkable ; and various opinions are recorded by the older anatomists as to whether the Elephant did or did not possess a gall-bladder, most of them denying its existence, while others mistook enlargements of the biliary canals for a true vesieulumfellis.
The gall-bladder of the Elephant (fig. 480) is, in fact, situated between the coats of the duodenum itself, (b, c, e, p,) quite at the ter mination of the biliary duct which comes im mediately from the liver. It consists of a great oval pouch divided by transverse valves or septa into four compartments (n, o). The fundus and walls of this pouch are studded with glan dular granules ; the bile enters it at one ex tremity from the hepatic duct, (f, g,) and at the opposite end passes into the interior of ,the intestine (a, d, e, c) through a mamillary projection, situated upwards of two feet from the pylorus, through the orifice of which the point of a probe (q, r) is represented as pro truding. The arrangement of the pancreatic conduits is likewise remarkable. The pancreas consists of a loose arrangement of glandular rnasses not very closely connected with each other, from which separate ducts are given off, which terminate in a common canal. This latter, however, soon divides into two branches, one of which pours the secretion which it con veys into the upper compartment of the biliary pouch, where it is mixed up with the bile therein contained prepamtory to its introduction into the intestine, while the other branch of the pan creatic duct opens into the duodenum itself, about two inches lower down, so that at the orifice bile mixed with the pancreatic secretion enters the duodenum, while from the lower aperture the fluid received is pure pancreatic juice.