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HUMAN PHYSIOLOGY 



Taste Cells 



^Supporting 

 Cells 



A, isolated taste bud, from 

 whose upper free end 

 project the ends of the 

 taste cells; S, supporting 

 or protecting cell; C, 

 sensory cell. 



-Wall 



easily found on your own tongue if a drop of vinegar is placed on 

 its broad surface. In the folds, between these projections on the 



top and back part of the tongue, are lo- 

 cated the organs of taste. These organs are 

 called taste buds. 



Each taste bud consists of a collection of spindle- 

 shaped nerve cells, each cell tipped at its outer 

 en'd with a hairlike projection. These cells send 

 inward fibers 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 lo- 

 cated near the back of the tongue are stimulated only by a bitter 

 taste. Sweet substances are per- 

 ceived by cells near the tip of the 

 tongue. A substance must be 

 dissolved in fluid in order to be 

 tasted. 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. This 

 may easily be proved by holding the nose and chewing, with closed 

 eyes, several different substances, such as an apple, an onion, and 

 a 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 forebrain by means 

 of the olfactory nerv^e. In order to perceive odors, it is necessary 

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

 air over the olfactory cells so as to bring more odoriferous particles 

 to them and thus to distinguish the odor. 



'' Effects of Alcohol upon Taste and Smell. — The habitual use 

 of drinks containing alcohol, of tobacco, and of very strongly 



Taste Buds^: 



Nerves 



Section of cir cum vallate papilla. 



