THE SPECIAL SENSES. 189 



which are of microscopic size, resembling those that 

 abound in the fingers, and in other parts of the body 

 that have the sense of touch. Others are much larger, 

 and give to the tongue its roughness of feeling and ap- 

 pearance. Through the medium of these papillae, the 

 tongue receives impressions of touch and temperature, as 

 well as taste : indeed, its extremity is fully as delicate, in 

 respect to tactile sensations, as the tips of the fingers them- 

 selves. It can recognize the two points of the compasses 

 when separated not more than one-twenty-fourth of an 

 inch; the back of it is much less sensitive to touch, while 

 at the same time it is more highly sensitive to impressions 

 of taste. 



31. Each lateral half of the tongue resembles the other 

 in structure, and each receives the same number of nerves 

 three. One of these regulates motion, the other two are 

 nerves of special sense. One of the latter supplies the 

 front half of the tongue, and is called the gustatory nerve. 

 This is a branch of the great cranial nerve, called the 

 "fifth pair," which ramifies in all parts of the face. The 

 back of the tongue is endowed with the power of taste 

 through a nerve known as the glosso-pliaryngeal, because 

 it is distributed both to the tongue and throat. This dif- 

 ference in the nervous" supply of the tongue becomes signif- 

 icant, when we learn, as we shall presently, that each part 

 of it perceives a different class of flavors. 



32. The Sense of Taste. Taste is the special sense 

 by means of which we discover the savors, or flavoring 

 properties of the substances, which* come in contact with 

 the tongue. Mere contact with the surface of the tongue, 

 however, is not sufficient, but contact with the extremities 

 of the nerves of taste within the papillae is required. In 

 order that the substance to be tasted may penetrate the 



3 1 . Resemblance fn the parts of the tongue ? Powers and functions of thf 

 parts ? 



32. Taste ? What are the requisites to taste ? 



