94 ANATOMY OF THE RABBIT 



liver, and the pancreas. They are parts of an extensive series of 

 epitheHal glands, otherwise contained within the wall of the tube 

 and for this reason not appearing as gross structures. 



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



1. Oral Cavity 5. Small Intestine 



Vestibulum oris Duodenum 



Oral cavity proper Mesenterial intestine 



Jejunum 



2. Pharynx Ileum 



Nasal portion 



Oral portion 6. Large Intestine 



Laryngeal portion Caecum 



Vermiform process 



3. Oesophagus Colon 



Rectum 



4. Stomach 



Digestion as a Process 



The digestive system performs a variety of functions, both 

 mechanical and chemical, all connected directly or indirectly with 

 the digestion of food. In the oral cavity, solid food is divided into 

 small parts by the action of the teeth, and is mixed with salivary 

 secretion, so that it is more easily swallowed and passed along the 

 oesophagus to the stomach. The secretion of the oral glands is 

 thus important chiefly for the lubricating properties of 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 protein, and a coagulating action upon 

 milk. The liver secretion, known as bile, contains salts which co- 

 operate with the pancreatic secretion in its action upon fats and 

 which neutralize the acidity of the gastric secretion, thereby pre- 

 paring the contents of the intestine for the action of the pancreatic 

 juice and intestinal enzymes. The bile salts also aid in absorption 

 of the products of the digestion of fats. The pancreatic secretion 

 contains a variety of enzymes, degrading proteins and starches, and 

 breaking fats into fatty acids and glycerin. The microscopic glands 



