MANUAL OF NATURE 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. 
