78 , Anatomy of the Rabbit. 



The parts of the digestive tube may be classified as follows : 



1. Oral Cavity. 5. Small Intestine. 



Oral cavity proper. Duodenum. 



Vestibulum oris. Mesenterial intestine. 



Jejunum. 



2. Pharynx. Ileum. 



Nasal portion. 



Oral portion. 6. Large Intestine. 



Laryngeal portion. Caecum. 



Vermiform process. 



3. Oesophagus. Colon. 



Rectum. 



4. Stomach. 



The digestive system comprises a variety of functions, both 

 mechanical and chemical, and connected directly and indirectly 

 with the digestion of food. In the oral cavity solid food is com- 

 minuted by the action of the teeth, and is mixed with salivary 

 DIGESTION AS secretion, so that it is more easily swallowed 



A PROCESS. '^^^ passed along the oesophagus to the 



stomach. The secretion of the oral glands is 

 thus important chiefly for its mucous element, but that of the 

 parotid especially contains an enzyme, ptyalin, which is capable 

 of converting starch into soluble material. Food is further reduced 

 to a pulp-like mass in the stomach, while the gastric secretion, 

 containing pepsin and rennin, exercises a dissolving action upon 

 proteid, and a coagulating action upon milk. The liver secretion, 

 known as bile, contains, in addition to coloring materials, salts 

 which exert a splitting action upon fats. The pancreatic secretion 

 contains a variety of enzymes, converting proteids and starches, 

 and breaking fats into fatty acids and glycerin. The actions of the 

 dissolving enzymes is successive, secretion being dependent to some 

 extent on antecedent bodies by which the stimulus for secretion is 

 determined. Tha preHminary processes of digestion refer in this 

 way to the mechanical action of food passage along the canal, 

 and to the provision of converting enzymes. Absorption, which 

 the final object of the digestive process is accomplished chiefly 

 in the large intestine through the bloodvessels and lymphatics of 



