XX. DIGESTION AND ABSORPTION 



Problems. — To determine where digestion talces place by ex- 

 amining : — 



( a) The functions of glands. 



(b) The work done in the mouth. 



(c) The work done in the stomach. 



(d) The work done in the small intestine. 



(e ) The function of the liver . 



To discover the absorbing apparatus and how it is used. 



Laboratory Suggestions 



Demonstration of food tube of man (manikin). — Comparison with food 

 tube of frog. Drawing (comparative) of food tube and digestive glands 

 of frog and man. 



Demonstration of simple gland. — (Microscopic preparation.) 



Home experiment and laboratory demonstration. — The digestion of 

 starch by saliva. Conditions favorable and unfavorable. 



Demonstration experiment. — The digestion of proteins with artificial 

 gastric juice. Conditions favorable and unfavorable. 



Demonstration. — An emulsion as seen under the compound microscope. 



Demonstration. — Emulsification of fats with artificial pancreatic 

 fluid. Digestion of starch and protein with artificial pancreatic fluid. 



Demonstration of "tripe" to show increase of surface of digestive tube. 



Laboratory or home exercise. — Make a table showing the changes pro- 

 duced upon food substances by each digestive fluid, the reaction (acid or 

 alkaline) of the fluid, when the fluid acts, and what results from its action. 



To the Teacher. — The chief purpose of this chapter is to make plain the chem- 

 ical changes that take place during the process of digestion. The experiments given 

 have been found to be much more useful for immature minds of first-year students 

 than a longer series of conditions, which, although necessary for the fulfillment of 

 the technically correct experiment, are nevertheless extremely confusing to the 

 beginner. We here deliberately sacrifice some of the factors in the experiment in 

 order to maintain interest and obtain understanding. 



The absorption of foods is a difficult subject even for the adult, so experimental 

 work is not deeply treated. Nor should much more than memory work be ex- 

 pected at this time because of the several factors involved and the extreme diffi- 

 culty of their control. We cannot expect our teachers, much less our pupils, to 



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