By the assimilation of the food, I mean its conversion into a part of the living body. This is effected by a series of processes, each of which is preparatory to that which follows it. Most of them have been named.

Prehension is the act by which the food is taken into the mouth. At pasture the grass is seized by the lips, compressed into a little bundle, and placed between the front teeth, which separate it from the ground, by incision, aided by a sudden jerk of the head. In stable-feeding, the lips and teeth are used in nearly the same way. They seize the food and place it within reach of the tongue, but they produce no change upon it. The front teeth have less to do in stable than in field-feeding, but in neither case do they masticate the rood. Prehension of fluids is performed by sucking The lips are dipped in the water, and the cavity of the mouth is enlarged by depressing the tongue, by bringing it into the channel - the space between the sides of the lower jaw. Prehension may be difficult or interrupted by palsy or injury of the lips, soreness of the tongue, or loss of the front teeth. Colts often experience difficulty in grazing while changing the teeth. They lose flesh for a while, and, if they lose much, some rich fluid or salt boiled food may be given till the mouth get well. Horses that have lost one or two of their fore-teeth by falls, become unfit for turning out. Those that have lost a large portion of the tongue can not empty a pail.

They can drink none unless the nostrils be under water; but when only a small portion of the tongue has been lost, they have no difficulty. They can empty the pail. No horse can drink freely with a bit, particularly with a double-bit, in his mouth. It confines the tongue, and prevents close contact of the lips at the corners; as much air as water enters the mouth.

Mastication, the act of grinding the food, is performed altogether by the back-teeth. The food is placed between them by the tongue. Mastication is the first change which the food undergoes. It is broken into small particles, easily penetrable by the juices in which the food is about to be dissolved. In many old horses, and even in some young ones, mastication is imperfect, from irregularity or disease of the teeth. When the horse feeds slowly, holds his head to one side, drops the food from his mouth half-chewed, and passes a large quantity unaltered, his teeth should be examined. One may be rotten, broken, or projecting into the cheek, or into the gum opposite.