THE SENSE OF TASTE. 413 



part of the tongue. Strong evidence in favor of the specific difference between 

 various taste-nerves is found in the fact that the same substance may excite a 

 different gustatory sensation according as it is applied to the front or the back 

 of the tongue. Thus, it has been demonstrated that a certain compound of 

 saccharin (para-brom-benzoic sulphimide) appears to most persons to be sweet 

 when applied to the tip of the tongue, but bitter in the region of the circum- 

 vallate papillae. 1 



Oehrwall 2 has examined the different fungiform papillae scattered over the 

 tongue with reference to their sensitiveness to taste-stimuli. One hundred and 

 twenty-five separate papillae were tested with succinic acid, quinine, and sugar. 

 Twenty-seven of the papillae gave no response at all, indicating that they were 

 devoid of taste-fibres. Of the remaining ninety-eight, twelve reacted to suc- 

 cinic acid alone, three to sugar alone, while none were found which Mere acted 

 upon by quinine alone. The fact that some papillae responded with only one 

 form of taste-sensation is again evidence in favor of the view that there are 

 separate nerve-fibres and endings for each fundamental sensation ; but the 

 figures given in the experiments show that the majority of the papillae are 

 provided with more than one variety of taste-fibre. 



An extract of the leaves of a tropical plant, Gymnema silvestre, when 

 applied to the tongue, renders it incapable of distinguishing the taste of sweet 

 and bitter substances ; it probably paralyzes the nerves of sweet and bitter 

 sensations. When a solution of cocaine in sufficient strength is painted on 

 the tongue, the various sensations from this member are said to be abolished 

 in the following order: (1) General feeling and pain; (2) bitter taste; (3) 

 sweet taste ; (4) salt taste ; (5) acid taste ; (6) tactile perception (Shore). 



That there are laws of contrast in taste-sensation has long been empirically 

 known. Thus, the taste of cheese enhances the flavor of wine, but sweets 

 impair it (Joh. Miillcr). It is unfortunate, from a hygienic standpoint at 

 least, that in this most important department of the physiology of sensation 

 investigations are almost wholly wanting. 



Certain tastes may disguise others without physically neutralizing them ; 

 when, for example, sugar is mixed with vinegar, the overcoming of the acid 

 taste is probably effected in the central nerve-organ. 3 



1 Howell and Kastle: Studies from the Biological Laboratory of Johns Hopkins University. 

 1887, iv. 13. 



2 Skandinavisches Archil) fitr Physwlogie, 1890, vol. ii. S. 1. 



3 Briicke: Vorlemngen iiber Physiologie, 1876. 



