TASTE WITHOUT SAPIDITY. 379 



sugar cannot be perceived, and the .tactile sensibility of the tip of the 

 tongue is also diminished. 



Gustatory impressions sometimes arise independently of the contact 

 of sapid bodies with the organ of taste. A drop of pure water placed 

 on the tongue, gives rise to a slightly bitter taste; and the same sen- 

 sation is caused by touching its surface near the root, with a dry glass 

 rod. A cool saline taste, somewhat resembling that of nitre, is pro- 

 duced by directing a small current of air on to the tongue. (Henle.) 

 Electricity also gives rise to gustatory impressions, a peculiar saline 

 taste being caused, when the front of the tongue is stimulated by 

 electrical shocks ; whilst a constant current produces a sour taste at 

 the positive pole, and an alkaline impression at the negative pole, per- 

 haps from decomposition of the secretions of the mouth. Indistinct 

 gustatory sensations may be induced by striking sharply and lightly 

 the lingual papillae. A mechanical stimulus applied to the fauces and 

 root of the tongue, induces a bitter taste, and a sensation of nausea. 



The sense of taste presents different degrees of development in dif- 

 ferent individuals, being, in some, much more acute than in others. 

 Like the other senses, it is improved by cultivation, as is well seen in 

 the case of wine- and tea-tasters. In colds, and diseases and injuries 

 of the brain, the sense of taste is lost, either temporarily or perma- 

 nently. 



Impressions made upon the sense of taste, remain for a certain time ; 

 those produced by some substances lasting for a considerable period. 

 As a rule, they endure longer than the after impressions of smell, hear- 

 ing, or sight. The after taste, or arriere gout, has its seat at the root 

 of the tongue; like taste, it can be strengthened by pressing, rubbing, 

 and moving the sapid body between the palate and the tongue. The 

 after taste frequently differs from the original one; a bitter substance 

 may give rise to a sweet after impression, or a sweet substance to a 

 bitter one. 



Subjective gustatory impressions sometimes occur, as, for example, 

 metallic, sweetish, and sanguineous or nauseous tastes. These subjec- 

 tive sensations have been supposed to proceed from changes in the 

 composition of the blood, which are perceived in the interior of the 

 organ of taste. They may bs due to errors in the circulation through 

 the nervous centres connected with taste; and sometimes merely to an 

 altered condition of the secretions of the mouth. A person suffering 

 from the disease known as saccharine diabetes, in which sugar exists 

 in undue quantity in the blood, is not, however, conscious of a sweet 

 taste, and can readily distinguish sugar ; whilst a taste of blood is 

 usually only experienced when the cavity of the mouth contains blood. 



The sense of sight, as is well known, materially influences the gus- 

 tatory sense ; for, in the dark, sapid substances lose half their relish. 



The uses of the sense of taste are, besides that of imparting gratifi- 

 cation, chiefly to assist in the choice of food. This is often peculiarly 

 manifested in invalids or convalescent persons. 



