402 ORGANS OF THE SENSES. 



tastes / but these are a feature of general sensibility : a sub- 

 stance of an acrid taste has a tendency to destroy the raucous 

 surface, as if by a blister ; we therefore designate as acrid 

 those substances which modify, eat into, or dissolve the epi- 

 thelium. 



On the other hand, sensations arising only from some im- 

 pression made upon the organ of smell are frequently mistaken 

 for gustatory impressions ; the organs of taste and smell are 

 situated so near each other, that it would seem that their 

 sensations must be connected. Aromatic, nauseous sensa- 

 tions, etc., belong to this class: thus roast meats, cheese, 

 some vinous and other drinks, owe their sapid properties to 

 the development of fatty acids or peculiar odoriferous ethers. 

 If we stop up the nostrils while eating, or have simply a cold 

 in the head, we find that most alimentary substances lose 

 their taste. 



It is more difficult to decide whether salt, alkaline, and 

 acid savors are actually gustatory sensations, or sensations of 

 touch in a disguised form. Schiff considers them to be really 

 gustatory impressions, because they are not perceived as such 

 when the cutaneous surface is excoriated, and also because 

 they are produced by the exciting influence of the galvanic 

 current : we know that this current gives rise to gustatory 

 sensations which are not caused by the electrolytic decom- 

 position of the buccal liquids, and which consist essentially 

 in an acid taste at the positive pole, and an alkaline taste at 

 the negative pole. However this may be, the acid and alka- 

 line sensations form a transition to the really gustatory sen- 

 sations. 



By excluding all the so-called savors which are produced 

 by such impressions as we have mentioned, we arrive at the 

 conclusion that there are really only two distinct tastes, 

 sweet and bitter, and only two kinds of really sapid bodies, 

 sweet and bitter. There is nothing to be said in general as 

 to those substances, between which there appears to be no 

 chemical connection ; for we find bodies in the class of chem- 

 ical substances which, in a chemical point of view, are most 

 dissimilar, such as salts of lead, sugars, properly so called, and 

 a number of alcohols (glycerine). 



By experimenting with these substances we find that the 

 posterior part of the upper surface of the tongue, its lower 

 surface, and the frcnum have no power to cause sensation of 

 tnste; this latter is confined to the edges of the tongue, espe- 

 cially to the tip. In these parts, beside the filiform or con- 



