SENSE OF TASTE. 401 



the result of excitation carried to the highest degree, for 

 many instances a?-e known of the sensibility to pain ceasing 

 entirely (analgesia), while all other forms of sensibility (touch, 

 tickling, to temperature) remained : in this case we must con- 

 clude that the nerve terminations have lost their suscepti- 

 bility to the higher degrees of excitation, while they are still 

 capable of being affected by the lower. 



II. THE SENSE OF TASTE. 



THE sense of taste is the result of special impressions pro- 

 duced by certain sapid substances; it is, however, difficult 

 exactly to define a sapid substance, and to analyze the interior 

 phenomenon of the impression produced by it; there is, also, 

 some difference of opinion in regard to the subject of dis- 

 tinguishing between the true sapid substances, and those 

 which only excite the general or tactile sensibility of the 

 organ of taste. 



The exclusive seat of taste is in the mouth. The palate is 

 commonly spoken of as the seat of this function, but physiolog- 

 ical experiments have proved that the sense of taste, par excel- 

 lence, resides only in the tongue, and is even restricted to 

 certain parts of this organ. In general, when we wish to 

 taste any substance, we place it upon the tongue and apply 

 the latter to the palate, in order to compress the sapid sub- 

 stance, and thus increase its points of contact with the gus- 

 tatory surface ; it is on account of this that the palate has 

 been wrongly supposed to have an office to perform in tast- 

 ing in addition to this simple mechanical duty. 



A fruitful cause of mistake, and one which ought to make 

 us distrust many experiments, lies in the fact that sensations 

 have been often mistaken for taste, while these were only 

 produced by the general or tactile sensibility of the tongue. 

 We have seen that this organ, especially its tip, must be 

 classed as the most important among the organs of touch : 

 certain sensations, dignified with the name of tastes, are 

 caused by this sensibility, such as the farinaceous savor re- 

 sulting from the mechanical impression produced by a sub- 

 stance divided in small pieces, and the gummy taste of 

 substances in a more or less sticky condition. What is 

 known as afresh or cooling taste, is only the thermal effect 

 produced by the absorption of caloric, caused by a substance 

 in dissolving (such as the taste of nitre), or in evaporating 

 (as the taste of the essential oils). We speak also of acrid 



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