MANUAL OP NATURB STUDY. 99 



Physiology. 



1. Review^ foods. See work for third year. 



2. Digestion. — a. Organs of. b. Functions of 

 each organ, c. Processes, d. Favorable and un- 

 favorable conditions. 



After a discussion of the foods, as suggested in 

 the Third Grade, put them through a process of 

 cooking, and then introduce the children to the 

 process of mastication, the first process in digestion. 



Teeth. — Number, kind, action. 



Saliva. — Show where it comes from, and what 

 excites it to action. Prove that one of its uses is 

 to enable the jaws, tongue and cheeks to work 

 smoothly with each other. 



To do this, have each child bring a clean napkin, 

 and, at the order of the teacher, mop out their own 

 mouths perfectly dry and immediately thereafter 

 try to chew or open the mouth, and work the 

 tongue. What result ? 



Again mop the mouth dry and immediately 

 thereafter put sugar on the tongue, and see if it 

 can be tasted. Try sand, and see if the child, 

 while the tongue and mouth are absolutely dry, 

 can detect the difference in taste. It must be then 

 that the saliva is used to dissolve solubles in the 

 mouth so as to give the tongue a chance to select 

 the good and reject the bad food. 



