TASTE. 481 



The only difference in the sensibility of these parts lies in the de- 

 gree of its development. 



But there are certain other sensations which are different in kind 

 from those perceived by the general integument, and which, owing 

 to their peculiar and special character, are termed special sensations. 

 Such are, for example, the sensation of light, the sensation of sound, 

 the sensation of savor, and the sensation of odors. The special 

 sensibility which enables us to feel the impressions derived from 

 these sources is not distributed over the body, like ordinary sensi- 

 bility, but is localized in distinct organs, each of which is so con- 

 stituted as to receive the special sensation peculiar to it, and no 

 other. 



Thus we have, beside the general sensibility of the skin and 

 mucous membranes, certain peculiar faculties or special senses, as 

 they are called, which enable us to derive information from ex- 

 ternal objects, which we could not possibly obtain by any other 

 means. Thus light, however intense, produces no perceptible sen- 

 sation when allowed to fall upon the skin, but only when admitted 

 to the eye. The sensation of sound is perceptible only by the 

 ear, and that of odors only by the olfactory membrane. These 

 different sensations, therefore, are not merely exaggerations of 

 ordinary sensibility, but are each distinct and peculiar in their 

 nature, and are in relation with distinct properties of external 

 objects. 



In examining the organs of special sense, we shall find that they 

 each consist First, of a nerve, endowed with the special sensibility 

 required for the exercise of its peculiar function ; and, Secondly, of 

 certain accessory parts, forming an apparatus more or less compli- 

 cated, which is intended to assist in its performance and render it 

 more delicate and complete. We shall take up the consideration 

 of the special senses in the following order. First, the sense of 

 Taste ; second, that of Smell ; third, that of Sight ; and fourth, that 

 of Hearing. 



TASTE. We begin the study of the special senses with that of 

 Taste, because this sense is less peculiar than any of the others, and 

 differs less, both in its nature and its conditions, from the ordinary 

 sensibility of the skin. In the first place, the organ of taste is no 

 other than a portion of the mucous membrane, beset with vascular 

 and nervous papillae, similar to those of the general integument. 

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