DIGESTION AND ABSORPTION OF NUTRIENTS 91 



the arrowroot cannot be obtained) equal to half the size 

 of a pea. 



1. Pour a small amount of the starch paste into a test tube, 



add some Fehling's solution, and boil. Is grape 

 sugar present ? How do you know? 



2. Put some saliva into a clean test tube. Test it with 



Fehling's solution as you did the starch. Does this 

 saliva contain grape sugar ? How do you know ? 



3. In another clean test tube pour some saliva into some of 



the starch paste, shake the mixture, and warm it 

 gently for a few moments to the same temperature 

 as that of the mouth. Now test with Fehling's 

 solution, as in 1 above. 



a. State what was done, the result, and the conclusion. 



b. What, therefore, is the effect of saliva on boiled starch ? 



c. Name several foods already studied that could be 



partially digested by saliva. 



4. (Optional home work.) Take some popped corn or shredded 



wheat into the mouth and chew it thoroughly. Can you 

 detect any sweet taste at first? Can you after chewing 

 for a time ? What does this experiment teach you as to 

 one advantage of thoroughly chewing the food ? 



122. Position and action of the salivary glands. In addition to 

 the mucus given out by the mucous membrane (113) the mouth 

 receives another secretion called saliva. At the sight or smell of 

 tempting food "the mouth waters." Saliva is secreted by the 

 salivary glands. Two of these glands (the parotids, from Greek, 

 meaning "beside the ear") are located near the back of the lower 

 jawbone just beneath and in front of the ear. Any one who has 

 had the mumps can readily locate these organs, for mumps is a 

 disease in which these glands swell. From the parotid gland of each 

 side a duct conveys saliva along through the walls of the cheek. 

 This duct opens at the top of a small elevation, which may be felt 

 with the tip of one's tongue opposite the upper second molar teeth. 



Two other pairs of glands (the submaxillary, Latin, sub = be- 

 neath + maxilla = jawbone, and the sublingual, Latin, sub = 



