PHYSIOLOGY OF GUSTATION 153 



sugar. Hooper (1887) extracted from the leaves of this 

 plant a compound that he named gymnemic acid and that 

 he showed to be the substance that affected taste. Ac- 

 cording to him gymnemic acid tends to obliterate the 

 sweet and bitter tastes but has no effect on the saline and 

 sour tastes. Shore (1892) studied the influence of gym- 

 nema decoctions on the tongue and found that they oblit- 

 erated the sweet taste of glycerine very easily and the 

 bitter taste of quinine almost as readily. They had very 

 little effect on the taste of sulphuric acid or of common salt. 

 These results were confirmed in the main by Kiesow 

 (1894). Thus gymnemic acid divides the tastes into at 

 least two distinct classes, one including sweet and bitter, 

 and the other sour and saline. 



Stovaine is also known to abolish sweet and bitter 

 without obliterating saline and sour (Ponzo, 1909) and 

 eucaine-B especially reduces bitter (Pontana, 1902). 

 Saline and sweet tastes and in less degree bitter are 

 reduced by a 0.02 normal solution of chromium nitrate 

 (Herlitzka, 1909). 



The effect of cocaine on taste is very profound. Von 

 Anrep (1880) and Knapp (1884) observed that this nar- 

 cotic was capable of abolishing completely all taste. 

 Aducco and Mosso (1886) showed, however, that it acted 

 more energetically on the bitter taste than on the others. 

 Shore (1892) found that on treatment with cocaine the 

 buccal sensations were extinguished in a definite order 

 as follows : pain, bitter, sweet, saline, sour, and touch, a 

 sequence confirmed by Kiesow (1894). Thus cocaine is 

 more selective in its effect on taste than gymnemic acid 

 and leads to a separation of all four tastes. 



11. Substances with two Tastes. A number of sub- 



