DIGESTION. 47 



and naturally we expect to find his digestive apparatus suited to dis- 

 integrating and dissolving all kinds of food. 



In him the digestive apparatus consists of a long tube, called the 

 alimentary canal, about thirty feet in length, with its accessories, the 

 teeth and the various glands which empty their products into the tube 

 by means of little ducts. 



The alimentary canal is the long tube beginning with the mouth 

 and ending with the anus, composed of muscle and mucous membrane, 

 the latter lining it throughout its entire length and giving to the 

 interior of the canal its characteristic smoothness and redness. In 

 this lining membrane, as also in the submucosa, are located some of 

 the glands whose secretions aid digestion. 



The alimentary canal in its extent of about thirty feet has 

 received various names for its several parts. They are: mouth, 

 pharynx, oesophagus, stomach, small and large intestines. 



The mouth is an oval box situated at the commencement of the 

 canal, in which, by the action of the jaws with their two rows of teeth, 

 the hard parts of the food are masticated. While the food is being 

 masticated, it is at the same time being mixed with a watery fluid, 

 the saliva, the secretion of the salivary glands; this mixing .of food 

 and saliva has been termed insalivation. 



In the pharynx and oesophagus occurs the act of deglutition, or 

 swallowing of the masticated mouthful, in the form of a large, moist 

 bolus. It is by the contraction of the muscles in these parts, that the 

 food is quickly passed on to the stomach. The course of the tube, 

 beginning with the mouth and ending at the opening of the stomach, 

 is comparatively straight, and measures about fifteen or eighteen 

 inches in length. This part of the tube is found in the head, neck, 

 and thorax, ending just below the transverse muscular wall of the 

 trunk, the diaphragm. 



The stomach is the muscular pouch in which occur some of the 

 chemical changes of the food, converting it into a grayish-brown soup- 

 like mass. From thence it passes into the small intestine, where the 

 nutrient materials are separated from the waste-residue; the latter 

 is passed on into the large intestine to be later expelled from the body. 



The stomach and the large and small intestines are located in the 

 abdomen and pelvis, differing from that part of the canal above the 

 diaphragm in that the intestines are much folded and convoluted in 

 their course; so that the major portion of the entire length of the 

 canal is contained here. 



In the mucous membrane and submucosa are located micro- 



