yo8 THE SENSE OF TOUCH. 



But, although, all parts of the body supplied with sensi- 

 tive nerves are thus, in some degree, organs of touch, yet 

 the sense is exercised in perfection only in those parts the 

 sensibility of which is extremely delicate, e.g., the skin, 

 the tongue, and the lips, which are provided with abun- 

 dant papillse. (See chapter on SKIN, and section on 

 TASTE.) 



The sensations of the common sensitive nerves have as 

 peculiar a character as those of any other organ of sense. 

 The sense of touch renders us conscious of the presence of 

 a stimulus, from the slightest to the most intense degree 

 of its action, neither by sound, nor by light, nor by colour, 

 but by that indescribable something which we call feeling, 

 or common sensation. The modifications of this sense 

 often depend on the extent of the parts affected. The 

 sensation of pricking, for example, informs us that the 

 sensitive particles are intensely affected in a small extent ; 

 the sensation of pressure indicates a slighter affection of 

 the parts in a greater extent, and to a greater depth. It 

 is by the depth to which the parts are affected that the 

 feeling of pressure is distinguished from that of mere 

 contact. Schiff and Brown-Sequard are of opinion that 

 common sensibility and tactile sensibility manifest them- 

 selves to the individual by the aid of different sets of fibres. 

 Dr. Sieveking has arrived at the same conclusion from 

 pathological observation. 



By the sense of touch the mind is made acquainted with 

 the size, form, and other external characters of bodies. 

 And in order that these characters may be easily ascer- 

 tained, the sense of touch is especially developed in those 

 parts which can be readily moved over the surface of 

 bodies. Touch, in its more limited sense, or the act 

 of examining a body by the touch, consists merely in a 

 voluntary employment of this sense combined with move- 

 ment, and stands in the same relation to the sense of 

 touch, or common sensibility, generally, as the act of seek- 



