1402 TASTE SENSATIONS. [BOOK m. 



so applied as to produce little or no electrolytic effect, was able 

 to develope sensations of taste, varying in kind according to the 

 region of the tongue stimulated. When the electrodes are applied 

 to the tip of the tongue, the more usual result is that though 

 an acid taste is the most prominent, a mixed gustatory sensation 

 is developed, in which a sweet taste may be often recognised as a 

 constituent. In like manner a bitter constituent may be recog- 

 nised in the sensation developed when the electrodes are placed at 

 the back of the tongue. If the tongue be previously subjected 

 to the influence of Gymnema, the taste at the tip is free from all 

 sweetness and that at the back free from all bitterness, the 

 sensations which are then experienced being variously described as 

 simply " metallic," or " salt " or " acid." From this result we may 

 draw the important inference that the interrupted current 

 developes a bitter and a sweet taste by acting in some way or 

 other directly on the specific terminal organs of the two respective 

 tastes, very much in the same manner as do bitter and sweet 

 things. 



We have already said that when an acid, especially a some- 

 what strong acid, is placed on the tongue or in the mouth, the 

 pure gustatory acid sensation is apt to be confused with the 

 sensation of pungency, the affection of general sensibility which 

 the acid also brings about and which speedily merges into pain. 

 These two sensations may be differentiated by means of cocaine. 

 If the tongue be painted with a weak solution of cocaine, the 

 general sensibility, the groundwork so to speak of pain, is abolished, 

 while the pure gustatory sensations are at first hardly affected at all ; 

 a relatively strong acid which previously made the tongue "smart" 

 so that real gustatory sensations were obscured, now developes a 

 pure ' rich ' acid taste alone. It is moreover said that cocaine 

 applied to the tongue in increasing strength of solution abolishes 

 the several classes of sensations in the following order : general 

 sensibility and pain, bitter taste, sweet taste, salt taste, acid taste, 

 tactile sensations. 



Taking all these facts, and others which we might bring- 

 forward, into consideration, we are led to the conclusion that 

 the development of the several kinds of gustatory sensations 

 depends on the presence of specific terminal organs in the surfaces 

 by means of which we taste. There appear to be distinct terminal 

 organs for bitter tastes, for sweet tastes, for acid tastes, for salt 

 tastes, and possibly for other tastes, all differing from the terminal 

 organs for tactile sensations, and from the structures whatever they 

 may be which are concerned in general sensibility. But beyond 

 this it is very difficult to say anything decisive. From the fact 

 that sensations of taste are, as a whole, most constant and most 

 acute at the back of the tongue, in the neighbourhood of the 

 circumvallate papillae in which taste-buds are present, we may 

 infer that the name taste-bud has been wisely chosen. But the 



