TASTE — SMELL 



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Each taste bud consists of a collection of spindle-shaped neu- 

 rons, each cell tipped at its outer end with a hairlike projection. 

 These cells send fibers inward to other cells, the fibers from which 

 ultimately reach the brain. The sensory cells are surrounded by 

 a number of protecting cells which are arranged in layers about 

 them. Thus the organ in longitudinal section looks somewhat like 

 an onion cut lengthwise. 



How we Taste. Four kinds of substances may be distinguished 

 by the sense of taste. These are sweet, sour, bitter, and salt: 

 Certain taste cells located near the back of the tongue are stimu- 

 lated only by a bitter taste. Sweet substances are perceived by 

 cells near the tip of the tongue, sour substances along the sides, 

 and salt about equally all over the surface. A substance must be 



Tash cells 

 Olfactory cells 



To brain ^__ _ 

 Nerve endings, of smell, taste, and touch (pressure). 



dissolved in order to be tasted. Taste and smell are often confused 

 and many things which we believe we taste are in reality perceived 

 by the sense of smell. Such are spicy sauces and flavors of meats 

 and vegetables. That we do not taste certain foods is proved by 

 closing the eyes, holding the nose, and chewing several different 

 substances in succession, such as apple, onion, and raw potato. 



Smell. — The sense of smell is located in the membrane lining 

 the upper part of the nose. Here are found a large number of rod- 

 shaped cells which are connected with the fore brain by means of 

 the olfactory nerve. In order to perceive odors, it is necessary to 

 have them diffused in the air ; hence we sniff so as to draw in more 

 air over the olfactory cells. 



Hearing. — The organ of hearing is the ear. The outer ear 

 consists of a funnel-like organ composed largely of cartilage which 



