THE SKIN AS AN ORGAN OP SENSE. 521 



all concerned with the various sensory impulses that originate 

 in the parts where they are found, but it is not possible at pres- 

 ent to assign definitely to each form its speciflc funqtion. 



It has been contended that the various specific sensations 

 of taste, as bitter, sweet, etc., are the result of impulses con- 

 veyed to the central nervous system by fibers that have this 

 function, and no other; and a like view has been maintained 

 for those different sensations that originate from the skin. 

 For such a doctrine there is a certain amount of support from 

 experiment as well as analogy ; but the more closely the subject 

 is investigated the more it appears that the complexity of our 

 sensations is scarcely to be explained in so simple a way as 

 many of these theories would lead us to believe. Whether 

 there are nerve-fibers with functions so specific, must be re- 

 garded as at least not yet demonstrated. 



Let us now examine into the facts. What are the different 

 sensations, the origin of which must be in the first instance, 

 sought in the skin, as the impulses aroused in. some form of 

 end-organ or nerve-termination ? 



Suppose that one blindfolded lays his left hand and arm 

 on a table, and a piece of iron be placed on the palm of his 

 hand, he may be said to be conscious of the nature of the sur- 

 face, whether rough or smooth, of the form, of the size, of the 

 weight, and of the temperature of the body ; in other words, 

 the subject of the experiment has sensations of pressure, of 

 tactile sensibility, and of temperature at least, if not also to 

 some extent of muscular sensibility. But if the right hand be 

 used to feel the object its form and surface characters can be 

 much better appreciated ; while, if the body be poised in the 

 hand, a judgment as to its weight can be formed with much 

 greater accuracy. The reason of the former is to be sought in 

 the fact that the finger-tips are relatively very sensitive in 

 man, and that from experience the mind has the better learned 

 to interpret the sensory impulses originating in this quarter; 

 which again resolves itself into the particular condition of the 

 central nerve-cells associated with the nerve-fibers that convey 

 inward the impulses from those regions of the skin. Mani- 

 festly if there be a sense referable to the muscles (muscular 

 sense) at all, when they are contracted at will the impression 

 must be clearer than when they but feebly respond to the mere 

 pressure of some body. 



