in THE SENSE OF TASTE 153 



VIII. Among the most important facts in the physiology of 

 taste is the observation that none of the four qualities, sweet, acid, 

 salt, bitter, can be subdivided into ut her components. Each taste is 

 an elementary quality that exhibits only quantitative differences; 

 it is not possible to pass gradually from one taste to another, as 

 in the colours of the solar spectrum and the tones of the musical 

 scale; as yet we have no rational criterion for arranging the four 

 tastes in a given order in series. 



We have seen, in speaking of the topography of taste, that 

 certain substances arouse different sensations according as they 

 are applied to the tip or the base of the tongue, and that in 

 general the sensibility to the four different primitive tastes is 

 differently distributed over the different segments of the taste 

 area. And we have seen the possibility of paralysing one or 

 other of the gustatory qualities by means of specific poisons. 



These facts collectively suggest, on analogy with what takes 

 place for the different sensitive points of the skin, that the 

 respective taste papillae differ specifically in regard to their excit- 

 ability by the four primary tastes. 



There is no proof of this in the histology of the peripheral 

 organs of taste, which fails to show any difference of structure 

 between the taste-buds of the papillae, such as it is possible up 

 to a certain point to see in the nerve-endings for cutaneous 

 sensibility. 



It is not possible to test the individual taste-buds like the 

 specific sensitive points of the skin. In many cutaneous regions 

 these are far apart, while the taste -buds are grouped in large 

 numbers in each papilla. About 400 buds lie in each of the 

 circumvallate papillae ; a lesser number in the fungiform. Each 

 bud, moreover, represents not a single nerve-ending, but a bundle 

 of sensory elements, so that it is not possible, as in the skin, to 

 excite each element individually. 



Still, it is interesting to excite the fungiform papillae 

 separately, to see if each of them reacts equally to the four 

 different tastes, or particularly or exclusively to one or two 

 tastes alone, according as the specifically dissimilar nerve-endings 

 conjectured are contained in each in an equal or unequal degree. 



This research, which is the application to taste of the method 

 of Blix for the skin, was undertaken successfully by Oehrwall, a 

 pupil of Blix (1891), on the fungiform papillae of the tip of the 

 tongue ; on these it is easy to carry out a series of methodical 

 experiments continued over several days upon the same group of 

 papillae, previously marked and numbered, so that they can be 

 easily recognised without any confusion. Highly concentrated 

 solutions were employed (40 per cent sugar, 5 per cent tartaric 

 acid, 20 per cent sodium chloride, 2 per cent hydrochloric, acid), 

 and brought into contact with the ends of the single papillae by 



