Hardesty, Spinal Nerves of the Frog. 9 1 



thetic system could be distinguished from those of the spinal 

 system. 



Kolliker ('45), opposing this idea of Bidder and Volkmann, 

 undertook a series of investigations which resulted in his being 

 forced to agree with them to the extent that, in addition to the 

 many nonmedullatcd nerve fibers having their origin in the 

 sympathetic system there do arise from the cells of the sympa- 

 thetic ganglia quite a number of medullated fibers also. Kolli- 

 ker found this to be true, not only for the frog but also 

 for other vertebrates. In a later paper, Kolliker ('94) 

 calls especial attention to these medullated sympathetic 

 fibers. He describes them as " dunkle randige Fasern " — 

 fibers possessing a thinner myelin sheath than that of the cere- 

 bro-spinal fibers, which sheath stains less black with osmic acid, 

 Kolliker also states that, while the great majority of sympa- 

 thetic fibers are " motor" in function, it is possible that there 

 are also among them "sensory " fibers which may play a role in 

 reflexes occurring in the domain of the sympathetic system. 

 Since Kolliker ('94), medullated fibers of sympathetic origin 

 have been often observed by Dogiel ('95 and '96) and others. 

 There is no doubt that for both mammals and the frog, some 

 sympathetic fibers are medullated. 



Some fibers from the sympathetic ganglia pass by way of 

 the nerve trunk to the spinal ganglia. By the observations of 

 Cajal ('93), Retzius ('94), Huber ('96), Dogiel ('96 and '97), 

 Cajal and Oloriz ('98) and others, it has been established that 

 for the frog and certain mammals at least, fibers having their 

 origin in the cells of the sympathetic ganglia, pass by way of 

 the ramus communicans and nerve trunk to the spinal ganglia 

 and end in pericellular plexuses about the cells there. Dogiel's 

 observations on medullated sympathetic fibers have been made 

 especially upon certain of these fibers going to and found in 

 the spinal ganglion. 



If sympathetic fibers pass to the spinal ganglia and end 

 there and if some of these fibers are medullated, then an enu- 

 meration of the medullated fibers on the distal side of the spinal 

 ganglion would include these medullated fibers which do not 



