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 produced 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 protein 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. This is done by the enzymes which cause digestion. It will be the purpose of this chapter to discover where and how digestion takes place in our own body.
