FOOD AXD DIGESTION 



IOI 



flow. Saliva is secreted only one fourth as fast when eat- 

 ing oatmeal and milk as when eating dry toast (Fig. 94). 



Fig. 94. — Cells of a Salivary Gland 



A, after rest, full of granules ; B, after short activity : C, after prolonged activity, cells 

 shriveled and granules lost. 



Starchy grains and fruits were eaten by early man without cooking, 

 and required more chewing than sweet, ripe fruits or oils or proteids. 

 Hence the saliva was given the power of acting upon the starch, for 

 it must remain in the mouth longer. The saliva is alkaline ; and if 

 the food is not thoroughly mixed with it, the stomach digestion will 

 also be imperfect, for the alkaline saliva is necessary to excite an 

 abundant flow of gastric juice in the stomach (Exp. 1). 



Eating slowly is difficult because of the grinding and cooking of 

 food ; hence the common practice of overeating. To eat slowly (1) do 

 not take large mouthfuls ; (2) do not take a second morsel until the 

 first has been swallowed ; (3) sit erect or lean back after putting food 

 into the mouth ; (4) the hands should lie idle most of the time. To 

 lean fonvard and keep food traveling to the mouth like coal into a 

 chute means overeating with all its bad effects. 



Chewing gum is a coarse and impolite habit, and wastes the saliva, 

 besides weakening the glands and irritating the stomach by the saliva 

 that is continually swallowed. Chewing tobacco has several of these 

 disadvantages, besides allowing the poison in the tobacco to be absorbed 

 by the mucous lining of the mouth. 



The pharynx (far'inks), or throat, is a muscular bag sus- 

 pended behind the nose and mouth. (See Fig. 89, also 

 Fig. 83.) There are seven openings into the pharynx: two 

 from the nostrils, two from the ears, one each from the 

 mouth, larynx, and gullet. Which of these openings are 

 downward ? Forward ? Lateral ? 



The gullet (or esophagus) is a muscular tube about nine 



