THE SENSES. 515 



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

 moistened with a sweet or bitter solution. The experiments of Duges, 

 Verniere, and Longet, have shown that taste resides in the whole 

 upper 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 pos- 

 sess the greatest amount of sensibility to savors, the middle portion of 

 its dorsum less, and its under surface little or none. As the whole 

 anterior part of the organ is supplied by the lingual branch of the fifth 

 pair, and the whole of its posterior portion by the glossopharyngeal, 

 it follows that the sense of taste is derived from both these nerves. 



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, they are sometimes liable to be 

 confounded with each other. The qualities which we perceive 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 qualities, which partake largely of the nature of ordinary physical 

 properties, appreciable by means of general sensibility. A starchy, 

 oily, or mucilaginous taste, when uncomplicated with additional savors, 

 is but little different in kind from tactile impressions. The quality of 

 pungency, communicated to the food by certain condiments, as pepper 

 or mustard, is appreciated altogether by the general sensibility. The 

 styptic taste seems to be an ordinary astringent effect combined with a 

 peculiar excitement of the gustatory 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 liquids, 

 such as tea, coffee, and wine, a great part of the effect produced is due 

 to the aroma or smell which reaches the posterior nares in the act 

 of swallowing. Even in many kinds of solid food, such as freshly 

 cooked meats, odor has an important share in the impression on the 

 senses. If, during the deglutition of such substances, the nares bo 

 closed, so as to suspend in great measure the sense of smell, their flavor 

 becomes nearly imperceptible ; and a similar effect is produced by catar- 

 rhal inflammation of the nasal passages, which impairs for the time 

 the sensibility of the olfactory membrane. 



Necessary Conditions of the Sense of Taste. There are certain con- 

 ditions requisite for gustatory impressions, beside the integrity of the 

 organ by which they are received. 



First, the sapid substance, in order that its taste may be perceived^ 

 must be in solution. So long as it remains solid, however marked a 

 savor it may possess, it gives no other impression than that of a foreign 

 body in contact with the tongue. But if applied in a liquid form, it 

 spreads over the mucous membrane, and its taste is perceived. Thus 

 it is only the liquid and soluble portions of the food which are tasted, 



