FOOD 



im 



Figure 186. — X-ray Photo- 

 graph of Appendix and 

 Part of Large Intestine. 



The constrictions are natural. 



opening of the rectum to the 



outside is the anus (a/ntts). 

 Glands. — A gland is a group 



of special cells which secrete a 



fluid. The glands which pro- 

 duce the digestive fluids are 



(1) the three pairs of salivary 



(sal'i-va-ry) glands, located 



below the ear, and beneath the 



tongue and lower jaw ; (2) the 



numerous gastric (gaVtrik) 



glands found in the lining of 



the stomach, possibly 5,000,000 



in number (Figure 187) ; (3) 



the pancreas; and (4) the liver, 



the largest gland in the body. 



145. Food. — One of the best definitions of food is the 



following. Food is that which when taken into the body 



builds up tissue or yields energy. All organic foods or 



foodstuffs are divided into three classes, 

 the proteins (pro'te-ins), the cdrhoh yd 'rates 

 (kar-bo-hi'drats), and the /ate. This classi- 

 fication is made whether we studv the 

 foods of a plant, an animal, or of man. 

 Scientists are able to tell to which class 

 meat, bread, oatmeal, milk, and all other 

 foods belong by finding out the chemical 

 composition of each. The chemists have 

 made a thorough study of food and tell 

 us that certain chemicals are present in 

 each of the three classes of foods. Defi- 

 nite chemical tests tell us to which of 

 these three classes any given article of food 



Figure 187. — \ ° . _ . 



Gastric Gland belongs. In general it may be said that the 



