THE SPECIAL SENSES 123 



sensibility which endow the tongue with painful, tactile, 

 or pressure and temperature sensations. One's sense of 

 taste, then, is highly complex, being easily associated 

 with, or influenced by, temperature, touch and odor. 



The numerous papillae of the tongue are provided 

 with certain cells ending in hairlike projections which 

 are peripheral taste organs. From these the sense of 

 taste is conveyed along the nerve paths mentioned to a 

 point in the temporospJienoidal lobe, just behind the 

 smell center, where the center for taste is thought to be 

 located. 



Because of their number and complexity, it is difficult 

 to classify taste sensations. The bitter, sweet, acid and 

 salt may be, and are, so often mingled not only with 

 each other, but with odors which w r e associate with 

 things tasted in the past that we can not separate the 

 various classes of stimulation. An apple, for instance, 

 is usually a combination of sweet and sour, but the 

 flavor so highly appreciated w r ould be lost if the olfac- 

 tory nerves were destroyed. It is for this reason that 

 food "loses its taste" when we suffer from colds, par- 

 ticularly if both the back and front of the nose is 

 stopped by secretion. The distribution of the four car- 

 dinal tastes is not clear, but the back of the tongue and 

 fauces are more sensitive to bitter and the front to 

 sweet stimuli. There is some evidence that there are 

 four separate end organs and nerve fibers for the four 

 fundamental tastes. 



A substance which is insoluble can not be tasted. A 

 piece of clean metal or glass stimulates the cutaneous 

 sensations when applied to the tongue, but gives no 

 sense of taste. Substances in solution, or capable of be- 

 ing rapidly dissolved in the saliva, give rise to sensa- 

 tions of taste, probably through a chemical reaction in 



