482 STUDIES IN ADVANCED PHYSIOLOGY. 



transmitted by the cells more effectively to the delicate 

 nerve filaments between them. Just like a finger, to use 

 the same illustration again, would be more susceptible if 

 placed between bricks in such a row. This variety of 

 touch corpuscle is designated as Grandry's corpuscle. 



THE ABSOLUTE TOUCH SENSITIVENESS. 



By the term of absolute sensitiveness is generally under- 

 stood the minimum stimulus which is yet able to produce a 

 sensation at the particular point in question. All parts 

 of the skin have not the same absolute sensibility. Things 

 which at certain portions produce no sensation at all are 

 at other places perceived with the greatest clearness.' The 

 highest absolute sensibility seems to be on the forehead, 

 where a minimum pressure of no more than .002 of a gram 

 is sufficient to produce a sensation. On the temples about 

 .05 of a gram; on the lower lip and fingers .5 of a gram, 

 on the forearm it requires 9 grams and on the skin of the 

 thigh as much as 17 to 20 grams. 



If instead of allowing a weight to rest, as was the case 

 in the determination of the figures just given, one should 

 take a hair or bristle of known stiffness and that should be 

 moved across the skin in question, the minimum pressure 

 perceivable is much reduced. In such experiments the 

 forehead perceives a pressure as little as .0007 of a grain; on 

 the arm or leg about .06. These figures of course corre- 

 spond with the experience of every one that the forehead, 

 skin of the face generally, the lips and fingers are able to 

 perceive differences in pressure which are entirely out of 

 the question on most other portions of the body. 



THE POWER OF LOCALIZATION AND THE TOUCH AREAS. 



The power to localize a touch sensation is a result of 

 experience. It may be materially improved by practice 

 but, other things being equal, the varioiis portions of the 

 skin show naturally a very different localizing ability. Thus, 

 at the tip of the tongue two points as close together as 



