94 Journal of Comparative Neurology. 



A splitting of the peripheral process of the cell {b) would 

 give two fibers on the distal side of the ganglion corresponding 

 to one fiber on the central side. This splitting or division of 

 the fiber has been observed by Stannius ('49) for fishes, Freud 

 ('78) for Petromyzon, and by Dogiel ('97) for mammals. Dog- 

 iel's observations however lead him to think that the splitting 

 more often occurs in the central rather than in the peripheral out- 

 growth of the spinal ganglion cell. Freud, on the other hand, 

 positively states that for Petromyzon the splitting occurs in the 

 peripheral process. 



That a splitting or division of fibers may be one cause of 

 the excess found on the distal side of the ganglion, is an expla- 

 nation which may have a better foundation than at first appears. 

 Dr. Elizabeth Dunn has just made, in this Laboratory, some 

 enumerations of the fibers contained in the trunk of the sciatic 

 nerve of the frog and also of the fibers contained in the several 

 branches into which this nerve divides for the innervation of the 

 leg. She kindly permits reference to be made to the fact that 

 she finds an appreciable excess of fibers in the branches. In a 

 frog [Rana viresccns) of about 50 grams weight there were found 

 in the trunk of the sciatic of one side, before any branches are 

 given off, 4293 fibers, while the sum of the fibers found in the 

 several muscular and cutaneous divisions to the thigh and in the 

 tibialis and pero7ieus branches to the lower leg, amounted to 

 45 1 1 fibers — an excess of 218. This excess of fibers in the 

 branches was found to be very similar for the two sides of the 

 same frog. 



The only explanation which suggested itself for this greater 

 number of fibers in the branches is that it was due to a splitting 

 of the fibers of the trunk of the sciatic. This probable and evi- 

 dently necessary splitting of the fibers called for by the results 

 of Dr. Dunn suggested an examination of the sciatic nerve es- 

 pecially at the points at which the branches are given off, for it 

 was thought that in these regions the splitting would most 

 probably occur. This investigation is as yet incomplete. 

 However at this stage abundant cases of divided fibers have 

 been observed in the branches of the sciatic of the second and 



