ASSIMILATION OF THE FOOD. 219 



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 dis- 

 solved. 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. 



Insalivation. — The food suflers mastication and insaliva- 

 tion at the same time. While under the operation of the 

 grinders it is moistened and diluted by a fluid which enters 

 the mouth at many little apertures. This fluid is almost 

 transparent ; it is tasteless ; it is termed saliva. Much of it 

 is furnished by two large glands, which are situated at that 

 part of the throat where the head joins the neck. These two 

 glands pour their secretions into the mouth by means of two 

 tubes which open near the grinding-teeth. Some have sup- 

 posed that the only use of this fluid is to dilute the food, and 

 to facilitate mastication and deglutition ; others, that it also, in 

 a slight degree, animalizes the food. Hence it has been argued 

 that the food should not be too soft, too easily eaten, lest it be 

 swallowed w^ithout insalivation, and without the animalization 

 which saliva ought to produce. It has been urged, as proof, 



