SEC. 4. GUSTATORY SENSATIONS. 



864. 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 membrane 

 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 recognised 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 experience 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 

 sensitive 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 sensation. Again, 

 when the interrupted current is applied to the tongue we not 

 only feel the contact of the electrodes but experience a peculiar 

 sensation which is probably due to the contractions excited by 

 the current in the muscular fibres of the tongue ; we say we " feel 

 the current." 



865. There are however certain sensations quite distinct from 

 those just mentioned and quite independent of smell which we 

 experience when various substances are placed in the mouth ; and 



892 



