THE SKIN AS AN ORGAN OF SENSATION 89 



elated with the sense of touch is that called the muscular 

 sense ( 95). By means of this sense we judge of the 

 weight of a body. When we hold an object in the hand we 

 feel its pressure upon the skin, and we also are conscious 

 of a muscular effort to support its weight. We lift it up, 

 move it from place to place, and by the amount of effort 

 put forth judge of the weight of the object. In this pro- 

 cess the muscles are involved as well as the cutaneous 

 organs of sensation. 



Again, we are conscious, even with our eyes closed, of 

 the position of the whole body. (This we shall find to be 

 connected with a certain part of the internal ear, 179.) 

 We are also conscious of the position of different parts of 

 the body in relation to one another, and when we come in 

 contact with external objects we perceive not only the 

 pressure from them affecting our organs of touch, but 

 also the pressure which we exert by muscular contrac- 

 tion upon them ; that is, the resistance to our movements 

 which is exerted by external things. It is sometimes 

 said that we have a "sense of effort" (or weight), a 

 " sense of position," and a " sense of movement," but 

 all these are included in the more general term, muscu- 

 lar sense. 



118. Pain. It is not yet fully determined whether the 

 sensation which we call pain is due merely to excessive 

 stimulation of the already known sensory organs, or is a 

 distinct sensation. Sometimes there is disease of sensory 

 tracts which destroys sensitiveness to pain, though the 

 sense of touch is unaffected. It may be that the nerve 

 fibers already referred to, which, distributed everywhere 

 through the body, constantly convey to the brain impres- 

 sions of which we are usually hardly conscious, and which 

 we call impressions of general sensibility, are the channels 



