3()2 LEWIS J. POLLOCK 



those ordinaril}^ used clinically. The sense of touch was tested 

 by a wisp of cotton. The sensation of pain in response to the 

 prick of a pin was ascertained by using a weighted needle sliding 

 within a bit of glass tubing so that with different weighted needles 

 a pressure of from 5 to 35 grams could be applied. 



It must be determined whether these methods are acceptable 

 as to the differentiation of epicritic and protopathic sensibility 

 and deep sensation. Light touch with a wisp of cotton to deter- 

 mine sense of touch may, I think, be accepted if exact threshold 

 of sensation is not under investigation, and if exact borders of 

 loss of sense of touch be not insisted on. For the purpose of 

 this investigation the exact borders of loss of sense of touch 

 need not be insisted on. Onl}^ one factor must be considered in 

 this method of examination; namely, return of so-called hair 

 sensibility must not be confused with touch; hence, in testing 

 for touch where an accurate border was to be determined, the 

 parts were closely shaven. 



The degree of pressure which it is permissible to employ in 

 determining prick pain without jeopardizing the results by 

 confusion with pressure pain remains to be discussed. Although, 

 as pointed out by Head and Sherren (4), deep sensibility may be 

 evoked when testing for touch with a stiff roll of wool, this objec- 

 tion is not valid for determining prick pain, within certain 

 limits. A sharp needle was used by Head and Sherren in their 

 early clinical investigations, care being taken to differentiate 

 betw^een sense of deep pressure and true pain. Boring {5) says 

 that ''In determining the pain threshold it was especially neces- 

 sary not to exceed pressures of 5 grams. Although at high 

 intensities of stimulus the introspective difficulty of abstracting 

 from pressure was less with pain than with cutaneous pressure, 

 the greater intensities frequently drew blood and therefore were 

 abandoned." As in Boring's work it was necessary to examine 

 a small area of skin repeatedly and at very short intervals for 

 all forms of sensation, his objection is valid. In my case, on the 

 other hand, it was necessary only to examine sense of prick 

 pain in areas of overlap and not to confuse this pain with pres- 

 sure pain. We have never found pain to result from 35 grams of 



