688 'Journal of Comparative Neurology and Psychology. 



1899j and used by the author in the previous investigations of 1900 

 and 1902. The photographic method was used for the larger trunks, 

 with the section constantly under observation through the micro- 

 scope for control, while the smaller trunks were counted under the 

 net. A high degree of magTiification was used in order to identify 

 the small medullated nerve fibers and any partly degenerated nerve 

 fibers, if such fibers were present. In almost every section from the 

 operated leg was found a small number of medullated nerve fibers 

 which had been stained a deep black, a few such nerve fibers were 

 observed in the intact leg. They were interpreted as nerve fibers 

 in process of degeneration showing drops of myelin and were not 

 included in the enumerations. It has been thought that a few 

 medullated nerve fibers are constantly breaking down in the periph- 

 eral nervous system. 



The question of the effect of degenerating nerve fibers upon adja- 

 cent supposedly intact nerve fibers has also been raised by some of 

 the conditions found in this frog. The facts noted are discussed in 

 the last section of this paper. 



Thanks are due for many helpful suggestions to Professor H. H. 

 Donaldson, now of The Wistar Institute of Anatomy and Biology, 

 at whose suggestion this study was begun, and to Professors R. R. 

 Bensley and C. J. Herrick of the University of Chicago. 



TABLE I. 



Names and designations of the primary nerve branches passing to the 

 muscles and skin of the thigh in the leopard frog, Rana pipiens. 



C. Nervus crural is. 

 S. Nervus ischiadicus. 



52. Ramus cutaneus femoris posterior. 



53. Ramus muscvilaris to the M. pyriformis. 



S4 »& S5. Rr. musculares to the M. gemellus and the M. obturator 

 internus. 



SG. R. profundus posterior. 



57. R. muscularis to the M. ilio-femoralis. 



58. R. profundus anterior. 



(S8x. R. muscularis to the M. ilio-fibularis.) 



