THE SENSES. 



remains. This is done by chewing the leaves of an Indian plant 

 (Gymnema sylvestre). It has also been shown that the power of tasting 

 sweet substances disappears before that of tasting bitter. Other experi- 

 ments have shown that the apparatus for salt and for acid tastes are 

 distinct. It is also demonstrable that bitters are most appreciated at the 

 back and sweets at the tip of the tongue, that salts are also most potent at 

 the tip, and acids at the sides of the tongue. All these tastes then, are 

 almost certainly provided with a distinct apparatus. It is clear there- 

 fore that the taste buds cannot be the only terminal organs for the sense 

 of taste, if from no other reason, at any rate from their exceedingly 

 limited distribution in the human tongue. 



Although the taste apparatus is bilateral the sensation or perception 

 is single, and in this respect taste resembles vision. 



After-taste. Very distinct sensations of taste are frequently left after 

 the substances which excited them have ceased to act on the nerve; and 

 such sensations often endure for a long time, and L modify the taste of 

 other substances applied to the tongue afterward. Thus, the taste of 

 sweet substances spoils the flavor of wine, the taste of cheese improves it. 

 There appears, therefore, to exist the same relation between tastes as 

 between colors, of which those that are opposed or complementary render 

 each other more vivid, though no general principles governing this rela- 

 tion have been discovered in the case of tastes. In the art of cooking, 

 however, attention has at all times been paid to the consonance or har- 

 mony of flavors in their combination or order of succession, just as in 

 painting and music the fundamental principles of harmony have been 

 employed empirically while the theoretical laws were unknown. 



Frequent and continued repetitions of the same taste render the per- 

 ception of it less and less distinct, in the same way that a color becomes 

 more and more dull and indistinct the longer the eye is fixed upon it. 

 Thus, after frequently tasting first one and then the other of two kinds 

 of wine, it becomes impossible to discriminate between them. 



The simple contact of a sapid substance with the surface of the 

 gustatory organ seldom gives rise to a distinct sensation of taste ; it needs 

 to be diifused over the surface, and brought into intimate contact with 

 the sensitive parts by compression, friction, and motion between the 

 tongue and palate. 



Subjective Sensations of Taste. The sense of taste seems capable of 

 being excited only by external causes, such as changes in the conditions 

 of the nerves or nerve-centres, produced by congestion or other causes, 

 which excite subjective sensations in the other organs of sense. But 

 little is known of the subjective sensations of taste; for it is difficult to 

 distinguish the phenomena from the effects of external causes, such as 

 changes in the nature of the secretions of the mouth. 



