602 THE SENSES. 



secretion by which its free surface is lubricated. The muscles of the 

 tongue are animated exclusive^ by filaments of the hypoglossal nerve. 



The exact seat of the sense of taste has been determined by placing in 

 contact with different parts of the mucous membrane a small sponge, 

 moistened with a solution of some sweet or bitter substance. The ex- 

 periments of Duges, Verniere, and Longet, have shown that taste resides 

 in the whole superior surface, the point and edges of the tongue, the soft 

 palate, fauces, and part of the pharynx. The base, tip, and edges of 

 the tongue possess the greatest amount of sensibility to savors, the 

 middle portion of its dorsum less, and its inferior surface little or none. 

 As the whole anterior part of the organ is supplied by the lingual branch 

 of the fifth pair alone, and the whole of its posterior portion by the 

 glossopharyngeal, it follows that the sense of taste is derived from both 

 these nerves. 



Furthermore, the tongue is supplied, at the same time and by the same 

 nerves, with general sensibility and with the special sensibility of taste. 

 The general sensibility of the anterior portion of the tongue, and that 

 of the branch of the fifth pair with which it is supplied, are sufficiently 

 well known. Section of the fifth pair destroys the sensibility of this 

 part of the tongue as well as that of the rest of the face. Longet found 

 that after division of the lingual branch of this nerve, the mucous mem- 

 brane of the anterior two-thirds of the tongue might be cauterized with 

 a hot iron or with potassium hydrate in the living animal, without pro- 

 ducing any sign of pain. Reid, on the other hand, determined that 

 ordinary sensibility exists in a marked degree in the glossopharyngeal 

 nerve, and is supplied by it to the parts in which its branches are dis- 

 tributed. 



A distinction is to be made, in the action of foreign substances taken 

 into the mouth, between the special impressions derived from their sapid 

 qualities, and the general sensations produced by their ordinary physical 

 properties. As the same substance is often capable of exciting both 

 tactile and gustatory impressions, the two are sometimes liable to be 

 confounded with each other The truly sapid qualities, which we per- 

 ceive by the special sense of taste, are savors, designated by the terms 

 sweet, bitter, salt, sour, alkaline, and the like. Beside these, however, 

 there are other characters, belonging to various articles of food, which 

 partake largely of the nature of ordinary physical properties, appreci- 

 able by means of general sensibility. A starchy, oily, or mucilaginous 

 taste, when uncomplicated with additional savors, is but little different 

 in kind from the tactile impressions produced by the same substances. 

 The quality of pungency, communicated to the food by the use of con- 

 diments, as pepper or mustard, is one which is appreciated altogether 

 by the general sensibility. The styptic taste seems to be a combination 

 of an ordinary astringent effect with a peculiar excitement of the gus- 

 tatory nerves, analogous to that caused by the galvanic stimulus. 



Furthermore, the taste or savor of a substance is to be distinguished 

 from its odoriferous properties or flavor. In most aromatic articles of 



