242 THE HUMAN BODY 



particles of substances which are being eaten reach the olfactory 

 region through the posterior nares and arouse sensations which, 

 since they accompany the presence of objects in the mouth, we 

 take for tastes. Such is the case, e. g., with most spices; when the 

 nasal chambers are blocked or inflamed by a cold in the head, or 

 closed by compressing the nose, the so-called taste of spices is not 

 perceived when they are eaten; all that is felt, when cinnamon, 

 e. g., is chewed under such circumstances is a certain pungency 

 due to its stimulating nerves of touch in the tongue. This fact 

 is sometimes taken advantage of in the practice of domestic 

 medicine when a nauseous dose, as rhubarb, is to be given to a 

 child. 



As the tongue, in addition to taste functions, possesses tactile 

 and temperature sensibility, its nerve apparatus must be complex; 

 and there is even reason to believe that different nerve-fibers 

 with presumably different end organs are concerned in the differ- 

 ent true tastes. Most persons taste bitter things better with the 

 back part of the tongue and sweet things with the tip, and in 

 some persons the separation of function is quite complete. Chem- 

 ical compounds are known which in such persons cause a pure 

 sweet sensation if placed on the tongue tip and a pure bitter sen- 

 sation if placed in the region of the circumvallate papillae; these 

 facts seem to show that the fibers concerned in bitter and sweet 

 sensation are distinct. Again, if leaves of a certain plant (Gym- 

 nema sylvestre) be chewed, the capacity to taste sweet or bitter 

 things is lost for some time, but salts and acids are tasted as well 

 as usual; and most persons taste salines better at the sides of the 

 tongue than elsewhere; so that the salt and acid sensations seem 

 to have a different apparatus, not only from the sweet and bitter, 

 but from one another. 



