222 'Journal of Comparative Neurology and Psychology. 



the areas in which the hairs do (C) and do not (B) respond to 

 stimulation with cotton wool. The dotted line separates the areas 

 in which plucking the hairs produced pain and no pain. Areas D 

 and E are areas in which the hairs reacted both to cotton wool and 

 to traction. Area C is the area in which plucking the hairs produced 

 a sensation similar to that of pressure or to that of brushing the 

 hairs, but in this area no pain was felt even when the hairs were 

 pulled out with their roots. In area B plucking of the hairs was ac- 

 companied by no pain and the hairs did not appear to be sensitive 

 to any form of stimulation. At times in this area, as happened 

 with the area near the elbow, when more than three or four hairs 

 were pulled simultaneously a sensation was obtained. This was 

 poorly localized, but appeared to be in neighboring more normal 

 areas. Here also it was found that the movement of the neighboring 

 parts appeared to be the determining factor in the production of the 

 sensation. The sensation from this form of stimulation was de- 

 scribed as similar to that of moving the hairs with cotton wool or 

 with the camel's hair brush, and also partly like that of lightly 

 touching the part with a blunt instrument. 



Wben this part of the arm was shaved it was found that cotton 

 wool could be appreciated in areas D and E. In these areas different 

 degrees of temperature could also be appreciated and the subject 

 reported marked sensation differences between cool and cold, and 

 between warm and hot stimuli.'' 



The above facts may be summarized as follows : WHien the ulnar 

 and median nerves are cut, over parts of the hand and arm it is 

 found that the hairs are not sensitive to plucking at a time when 

 lightly brushing the hairs on the same areas is appreciated as a 

 stimulus. The parts in which there is insensibility to plucking the 

 hairs are within the area that, in accordance with Head's differential 

 signs, may be described as possessing protopathic sensibility, but 

 in which the epicritic sensibility has been abolished. 



It appears, therefore, that we have in the hairs two forms of 

 sensibility, one for traction and the other for light pressures or 



'A full report of the tempera tiire findiugs in this portion of the arm will be 

 found in Section III of this article, beyond. 



