166 



LIFE PROCESSES OF MAN 



nerves. In the brain the food stimulus is interpreted as 

 sweet, sour, or bitter (Figure 181). 



LABORATORY STUDY 



Blindfold in turn several members of the class and have each hold his 

 nose while a small amount of some highly flavored food is placed on the 

 tongue. Such common foods as maple syrup, vanilla extract, marmalade, 

 jams, etc., are admirable for this test. Make a record of each test. This 

 experiment will prove that we do not taste flavors. Remove the hand from 

 the nose and again taste the same substances. This time there will be no 

 difficulty in telling the name of the substance because it has been smelled 

 as well as tasted. 



The roof of the mouth is called the palate. The front 

 part contains supporting plates of bone and is therefore 

 called the hard palate. The back part (the soft palate) is 

 a thin sheet of muscle covered by the mucous lining of the 

 mouth. The palate separates the mouth from the nasal 

 cavity. Beyond the soft palate is the throat cavity called 

 the pharynx. This is a funnel shaped cavity, having 

 two openings at its lower end, the front one being 

 the opening into the windpipe which leads to the lungs, 

 and the rear one, the opening into the esophagus. In 



the upper part of the 

 pharnyx on each side, is 

 the opening of an eusta- 

 chian (u-sta/ki-an) tube 

 which passes to the 

 middle ear. 



Teeth. — Just back of 

 the lips are the teeth. 

 In adults there are 

 thirty-two, sixteen in 

 each jaw, belonging to 

 four classes according to shape. In front are the eight 

 incisors (in-si'zers) with sharp cutting edges ; next the 



Figure 182. — Milk Teeth. 



Age 2>\ to 4 years. Notice the per- 

 manent teeth deeper in the jaws. 



