THE SENSE OF TOUCH. 555 



lips, which are provided with abundant papillae. (See chapter 

 on SKIN, and section on TASTE.) 



The sensations of the common sensitive nerves have as pe- 

 culiar a character as those of any other organ of sense. The 

 sense of touch renders us conscious of the presence of a stimu- 

 lus, from the slightest to the most intense degree of its action, 

 neither by sound, nor by light, nor by color, but by that inde- 

 scribable something which we call feeling, or common sensa- 

 tion. 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 patho- 

 logical 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 ascertained, 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 movement, and stands in the same relation to 

 the sense of touch, or common sensibility, generally, as the act 

 of seeking, following, or examining odors, does to the sense of 

 smell. Every sensitive part of the body which can, by means 

 of movement, be brought into different relations of contact 

 with external bodies, is an organ of "touch." No one part, 

 consequently, has exclusively this function. The hand, how- 

 ever, is best adapted for it, by reason of its peculiarities of 

 structure, namely, its capability of pronation and supination, 

 which enables it, by the movement of rotation, to examine the 

 whole circumference of a body ; the power it possesses of op- 

 posing the thumb to the rest of the hand ; and the relative 

 mobility of the fingers. Besides the hand, and especially 

 the fingers, are abundantly endowed with papillce and touch- 

 eorpuscles (pp. 336, 337) which are specially necessary for the 

 perfect employment of this sense. 



In forming a conception of the figure and extent of a sur- 

 face, the mind multiplies the size of the hand or fingers used 

 in the inquiry by the number of times which it is contained 



