164 ELEMENTS OF HIPPO LOGY, 



CHAPTER XIV. 



THE DIGESTIVE APPARATUS. 



The digestive apparatus consists of the mouth, the gullet, 

 the stomach, the large and small intestines, and certain 

 other organs, into whose functions it is not necessary to in- 

 quire in so elementary a treatise as this one. These organs ex- 

 cept, of course, the mouth and a portion of the gullet, are con- 

 tained in the abdominal cavity. 



The food is taken by the lips and is worked back to the 

 upper part of the mouth by the lips and tongue. There it is 

 masticated by the molar teeth and mixed with saliva secreted 

 by the salivary glands. This is the first process of digestion. 

 When the mouthful has been well broken up and saturated 

 with saliva, it is passed back through the pharynx and gullet 

 to the stomach. This is a small organ, having a capacity of 

 three to three and a half gallons. Two-thirds of the lining of 

 the stomach is a membrane that secretes gastric juice. The 

 food is slowly mixed in the stomach with this liquid until it 

 partially changes its character, and is passed into the small in- 

 testine, to be there mixed with the digestive juices of the liver, 

 spleen, and other intestinal glands, to be transformed by the 

 chemical action of these reagents until it is ready to be absorbed 

 into the system. 



A system of vessels, called lacteals, and the veins, absorb 

 the nutritive part of the food thus transformed and carry it to 

 a large vein near the heart, where it is poured into the blood. 

 This fluid, thus enriched, is carried by the circulation to all parts 

 of the body to nourish it and repair waste tissues. The debris 

 of digestion is forced through the large intestine and is voided 

 as dung. 



