THE DIGESTIVE SYSTEM. 115 



-of the tongue. The other pair of glands is called the sub- 

 lingual, placed under the tongue, they communicate with the 

 mouth close to the opening duct from the submaxillary. In addi- 

 tion to these we find other small glands connected with the 

 cheek and floor of the mouth, all of which assist in secreting 

 fluid to lubricate the bolus of food and perform the first stage of 

 digestion. Herbivorous animals secrete considerably more 

 saliva than the carnivora, which is rendered necessary by the 

 hard and woody nature of the food the animal is called upon to 

 consume. Situated on the floor of the mouth, and principally 

 filling that cavity, a pointed, rough, elongated body is found, 

 termed the tongue. This is principally muscular in structure 

 and very flexible. It is the special organ of taste, and also 

 materially assists in mastication and swallowing. In the sheep 

 it is a prehensile organ, assisting the lips in gathering the food 

 into the mouth. A decided difference in the back part of a 

 horse's and sheep's mouth is noticeable. While in the horse 

 the soft palate, situated in the entrance of the gullet, is sufR- 

 ciently long to fall down and completely close the back part of 

 the mouth, excepting when food is being swallowed, prohibiting 

 a horse from breathing otherwise than tlirough the nose, and 

 also preventing vomition, whereas in the sheep, being a ruminat- 

 ing animal, such a structure would be inapplicable, as it would 

 25revent the return of the contents of the first stomach to the 

 mouth, consequently the soft palate is considerably shorter and 

 nan'ower, not reaching the tongue. At the base of the tongue 

 we find the larynx and pharynx connected to the tongue and to 

 the upper jaw bone, or i-ather the bones of the head, by means of a 

 bone called the os hyoides. Adjoining the pharynx are two 

 spaces called the eustachian tubes, situated one on each side, 

 and communicating by means of a tube with the internal car. 

 At the superior extremity of the trachea, between the first and 

 fourth rings of that tube, are found two round, ovid bodies, one 



