376 LEWIS J. POLLOCK 



injury, nor does it return before tactile sensibility in the borders 

 between these areas where it is usually present when either 

 nerve is severed alone. 



3. WTien a region in the area of sensory distribution of a sev- 

 ered nerve is sensitive to cutaneous pain, and the region is 

 adjacent to another nerve area, if this nerve be severed complete 

 analgesia results in the previously sensitive region. 



4. When sensibility to prick pain is present or returns in the 

 area of possible overlap on to the sensory distribution of the 

 severed nerve, subsequent resection and suture of this nerve 

 does not change the general extent of this sensitive area, although 

 the borders may at times be slightly enlarged or diminished. 

 That is, the pain sense returned or present before the operation 

 was not due to partial regeneration. 



Because of these observations I believe that the early and 

 dissociated return of pain sense attributed by Head to the law- 

 less regeneration of protopathic sensibility is due to the assump- 

 tion of function of adjacent and overlapping nerves. 



It may still be contended that although the early return of 

 prick pain is due to nerve overlap, it is this type of sensation 

 which Head designates as protopathic. In other w^ords, we are 

 still confronted with the possible existence of two distinct sys- 

 tems of fibers for cutaneous sensibility. This is true, but one of 

 the most important links in the theory advanced by Head was 

 the temporal dissociation of the regeneration of the tw^o types of 

 sensory fibers. At least this part of the theory can be justly 

 criticized. 



Fig. 10 Sensory changes before and after resection of the K, F, sciatic nerve 

 and A, B, C, G, external popliteal nerve. 



K. Examined June 16, 1919 

 C. Examined May 30, 1919 

 G. Examined May 15, 1919 



A. Examined May 30, 1919 

 F. Examined June 29, 1919 



B. Examined June 5, 1919 



operated July 21, 1919; K' July 29, 1919. 

 operated July 7, 1919; C' July 29, 1919. 

 operated June 4, 1919; G' July 22, 1919, 

 operated July 9, 1919; A' August 9, 1919. 

 operated June 23, 1919; F' August 29, 1919. 

 operated May 1, 1919; B' May 31, 1919. 



