278 THE SPECIAL SENSES 



%f which we discover the savors, or flavoring properties of the 

 substances which come in contact with the tongue. Mere con- 

 tact 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 cells covering the nerves, it must 

 either be liquid in form, or readily soluble in the watery secre- 

 tion of the mouth the saliva. The tongue must be moist 

 also. If the substance be insoluble as glass or sand or 

 the tongue dry, the sense of taste is not awakened. In sick- 

 ness, when the tongue is heavily coated, the taste is very defec- 

 tive, or, as is frequently said, " nothing tastes aright.' 7 



33. All portions of the tongue are not alike endowed with 

 the sense of taste, that function being limited to the posterior 

 third, and to the margin and tip of this organ. The soft pal- 

 ate, also, possesses the sense of taste; hence, an article that 

 has an agreeable flavor may very properly be spoken of as pal- 

 atable, as is often done. All parts of the tongue do not per- 

 ceive equally well the same flavors. Thus, the front extremity 

 and margin, which is the portion supplied by the " fifth pair " 

 of nerves, perceives more acutely sweet and sour tastes ; but 

 the base of the tongue, supplied by the glosso-pharyngeal nerve, 

 is especially sensitive to salt and bitter substances. The nerve 

 of the front part of the tongue, as before stated, is in active 

 sympathy with those of the face, while the relations of the 

 other nerve are chiefly with the throat and stomach ; so that 

 when an intensely sour taste is perceived, the countenance is 

 involuntarily distorted, and is said to wear an acid expression. 

 On the other hand, a very bitter taste affects certain internal 

 organs, and occasions a sensation of nausea, or sickness of the 

 stomach. (Head Note 5.) 



5. Flavors and Sense of Taste. "The cause and intimate nature 

 of tastes are no better understood than those of odors. Flavors elude 

 analysis and defy classification, even that which divides them into agree- 

 able and disagreeable, for the taste of individuals and of nations singu- 

 larly differs in this respect. The Laplander and the Esquimau drink 



33. Portions of the tongue endpwed with taste ? Where else does the sense lodge ? 

 What is stated in respect to sweet and bitter flavors ? Reflex effects mentioned ? 



