1034 TASTE SENSATIONS. [Book hi. 



only and sugar the other only, the substance of which we are 

 speaking is able to affect both of them. In a somewhat similar 

 way certain salts, magnesium sulphate for instance, when applied 

 to the back of the tongue excite a bitterish taste, but when 

 applied to the tip of the tongue excite an acid or a sweetish acid 

 taste. 



We said a little while back that a weak interrupted current, 

 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 

 recognized as a constituent. In like manner a bitter constituent 

 may be recognized in the sensation developed when the elec- 

 trodes are placed at the back of the tongue. If the tongue be 

 previously subjected to the influence of G-ynmema, 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 infer- 

 ence 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 pungenc} 7- , 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 abol- 

 ished, 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 ob- 

 scured, 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 sur- 

 faces 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 



