XX. DIGESTION AND ABSORPTION 



Problems. To determine where digestion takes place by ex- 

 amining : 

 (a) The functions of glands. 



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 glcr.d. (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. Emulsificaticn 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. 



Purpose of Digestion. We have learned that starch and pro- 

 tein food of plants are formed in the leaves. A plant, however, is 

 unable to make use of the food in this condition. Before it can 

 be transported from one part of the plant body to another, it is 

 changed into a soluble form. In this state it can be passed from 

 cell to cell by the process of osmosis. Much the same condition 

 exists in animals. In order that food may be of use to man, it must 

 be changed into a state that will allow of its passage in a soluble 

 form through the walls of the alimentary canal, or food tube. 



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