ORGANS OF THE SENSES. 491 



ART. XXII. ORGANS OF THE SENSES. 



TOUCH. 

 Papillary Structure of the Skin. 



THE sense of Touch is the simplest as well as the most 

 universally diffused of the senses, it not merely extending 

 over every portion of the external surface of the body, but 

 also over certain of the internal mucous surfaces, as those of 

 part of the mouth, nose, &c. 



Over the general surface of the body this sense exists 

 under the form of common sensation ; and it is only in 

 certain parts, as on the palmar and plantar surfaces of the 

 hands and feet, that it becomes so highly developed as to 

 assume the importance of a distinct sense, and to deserve 

 the name of Touch. 



This sense has its seat in the papillary structure of the 

 skin, and the degree of the development of this structure, 

 as shown by the size and number of the papilla, is always 

 proportionate to the degree of perfection of the sense : thus 

 the papillae over the general surface of the body are much 

 less numerous and less perfect in form than they are in the 

 palms of the hands and soles of the feet. 



The papilla3 in the natural state are of course invested by 

 the epidermis, which indeed conceals them to a great extent 

 from view ; this requires to be removed by maceration be- 

 fore their form, size, and arrangement can be clearly as- 

 certained. 



After the removal of the epidermis, it will be seen that 

 the papillae on the general surfaces of the body do not follow 

 any definite arrangement, but are scattered here and there 

 without apparent order, more or less thickly according to 

 the degree in which the part of the integument upon 

 which they are seated is endowed with sensation, but every 



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