2 5 6 



HUMAN PHYSIOLOGY 



CHAP. 



5- Try the palm, the back of the hand, the forearm, the elbow, 

 the tip of the tongue, the back of the neck, etc. 



6. Cross your middle finger over the forefinger of the same hand 

 and touch the tip of the tongue to the crossed ends. What sensation 

 results ? In the same way, touch the point of the nose. 



174. The Sense of Taste. The tongue is the princi- 

 pal organ of taste. If you examine the upper surface 

 of the tongue carefully, three different kinds of papillae 



will be found. On 

 the back part of 

 the tongue there 

 are from seven to 

 eleven rather large 

 circular papillae. 

 On the tip and 

 sides the papillae 

 are slender, and 

 when largely de- 

 veloped, as in the cow and cat, they give a roughness 

 to the tongue. Papillae of a third class are scattered 

 over the tongue among the others. There are papillae 

 on the tongue, soft palate, and pharynx. In the papillae 

 occur little structures known as taste buds in which the 

 nerves of taste begin. The taste buds are sensitive to 

 sweet, sour, bitter, and salt. These are the chief sensa- 

 tions of taste. It is interesting to know that the tip of 

 the tongue is most sensitive to sweet, and the back of the 

 tongue to bitter. No substance can be tasted until it 

 has been dissolved and some of the solution comes in con- 

 tact with the nerve endings in tJie taste buds. 



FIG. 135. The tongue, showing the nerves of 

 taste and the papillae. (Drawn by Zuppke.) 



