22 .* ZOOLOGY. 



46. Ads of the Digestive Function. The phenomena 

 which take place in the different portions of the digestive tube 

 constitute a series of acts or functions all tending to one end. 

 They may be thus classed: 1. There is the prehension of 

 the food ; 2. The mastication ; 3. The insalivation ; 4. The 

 deglutition ; 5. The chymification, or stomachal digestion ; 

 (). The chylification, or intestinal digestion ; 7. Defsecation ; 

 8. The absorption of the chyle. 



Let us now examine these organs and their acts suc- 

 cessively, in man and in the animals which most approach 

 him. 



Prehension of the Food. 



47. That this act varies in different animals is evident. 

 Man employs the hands and mouth. Anatomically speaking, 

 the term mouth includes not only the opening so-called, but 

 the cavity into which it leads. This cavity is very complex, 

 but may be briefly described as having two orifices, one 

 externally, on the face, the other situated deeply, and leading 

 to the pharynx. Its boundaries are the palate above, the 



Fig. 6. Jacchus Penicillatus, Ouistiti a piuceau, Marmoset. 



tongue and floor of the mouth below ; at the sides the cheeks ; 

 behind, the moveable palate limits its extent, and serves the 

 important purpose of isolating it at times from the pharynx, 

 and of protecting the posterior nostrils. In man and in 

 many other animals the food is placed in the mouth by the 

 hands or anterior extremities; the lips retain it when so 

 placed. 



