34 ZOOLOGY. 



tion, there exist a peculiar principle called ptyaline and 

 animal diastase, various salts, as sea salt or chloride of 

 sodium, tartrate of soda, and a little uncombined soda, ren- 

 dering the saliva alkaline. 



The saliva thus mixed with the food facilitates mastica- 

 tion, assists in deglutition, and obviously aids in the digestion 

 of some kinds of food. 



Deglutition. 



59. In mammals, between the buccal cavity and the 

 pharynx, is a moveable muscular partition, the pendulous 

 palate (Fig. 31), which, during mastication, separates the 

 two cavities from each other ; but so soon as this is accom- 

 plished, the alimentary mass or bolus being pressed back- 

 wards by the tongue, the pendulous palate is drawn upwards 



Pendulous Palate. 



.___ yNose. 



Base of the Cranium. , """ 



t 

 Pharynx. Jf^jf^JjjKJ^^^^^^ Tongue. 



Salivary Glands. 

 Lingual Bone. 



Larynx. 



Thyroid Gland. 



Trachea or Wind- 

 (Esophagus. 



Fig. 31. Vertical Section of the Mouth and Throat in Man. 



and backwards, so as to permit of the passage of the food 

 or drink through the isthmus into the pharynx. At this 

 point deglutition commences, the term being applied to the 



