SEC. 2. GUSTATORY SENSATIONS. 



§ 639. The word taste is frequently used, when the word 

 smell ought to be employed. We speak of ' tasting ' odoriferous 

 substances, such as an onion, a wine, a savoury dish, and the 

 like, when in reality we only smell them as we hold them in 

 our mouth ; this is proved by the fact that the so-called taste of 

 these things is lost when the nose is held, or the nasal mem- 

 brane rendered inert by a catarrh. If the nose be held and the 

 eyes shut, it is very difficult to distinguish in eating between 

 an apple, an onion and a potato ; the three may be recognized 

 by their texture, but not by their "taste." Most of what we 

 call ' flavours ' appeal in reality to the sense of smell not to that 

 of taste. 



We also experience by means of the surfaces with which we 

 taste sensations other than those of taste. We feel by means of 

 the mucous membrane of the mouth sensations of the same kind 

 as those which we feel by means of the skin, and which we shall 

 study presently as tactile sensations or sensations of pressure, 

 sensations of heat and of cold ; indeed the tactile sensations of 

 the tip of the tongue are remarkably acute. We also experi- 

 ence by means of the mouth sensations of pain and other more 

 or less indefinite sensations which we shall presently speak of 

 as phases of " general " or " common sensibility;" and in this 

 respect the mucous membrane of the mouth is much more sensi- 

 tive than the skin towards chemical substances ; an acid for 

 instance or other corrosive liquid, in such a concentration as 

 when applied to the skin produces a sensation not essentially 

 different from that of mere contact with an innocuous liquid, 

 may when applied to the mouth produce a very painful sensa- 

 tion. Again, when the interrupted current is applied to the 

 tongue we not only feel the contact of the electrodes but expe- 

 rience a peculiar sensation which is probably due to the contrac- 

 tions excited by the current in the muscular fibres of the tongue ; 

 we say we " feel the current." 



§ 640. There are however certain sensations quite distinct 

 from those just mentioned and quite independent of smell which 



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