Ranson, spinal Nerves. Ill 



(Kleist and Koster); and there are plenty of cases of degenera- 

 tion in neurone chains similar to the disappearance of the cells 

 of the substantia gelatinosa — e. g., the degeneration of the motor 

 cells with their peripheral motor fibers after section of the dorsal 

 roots (Braeunig '03). He also cites, as bearing on this point, 

 the anomalous trigeminus found by v. Gudden in a calf, which 

 showed no sensory root fibers. The ganglion itself was normal, 

 as were also the fibers of the peripheral nerve arising from it, 

 although these peripheral fibers were greatly decreased in num- 

 ber. According to Nissl's view the fibers whose cells were 

 located within the brain had failed to develop, while those whose 

 cells were located in the Gasserian ganglion had developed nor- 

 mally. 



It would seem that these are rather insufficient grounds for 

 revising our conception of the dorsal root, based as it is on such a 

 large number of careful investigations; and it should be remem- 

 bered, in this connection that those who have worked with the 

 histology of the spinal ganglion, whether in teased preparations 

 or GoLGi-material, have considered the dorsal root fibers identi- 

 cal with the central branches of Ranvier's T-fibers. Of the 

 existence of some fibers in the dorsal root whose cells lie in the 

 cord, there can be no doubt, at least so far as certain of the lower 

 forms are concerned (Cajal '90; v. Lenhossek '90; and van 

 Gehuchten '93). 



According to the experiments of Joseph ('87) on the second 

 cervical nerve of the cat, these fibers are also found in mammals. 

 After section of the dorsal root, he has observed that some fibers 

 in the central portion remain normal and in the nerve a small 

 number degenerate. At first opposed by Singer and Munzer 

 ('90), these results of Joseph have been confirmed bythese same 

 authors in a later paper ('95) and anticipated by the earlier work 

 of Kahler ('84). KopczYNSKi ('o6) has been unable to verify 

 these observations. 



It is to be borne in mind that, while these direct observations 

 show the presence of fibers of passage in the spinal ganglion, they 

 also indicate that only a few fibers are of this category and that 

 these are efferent; and by no means do they support the view of 

 NissL that all the fibers of the dorsal root arise from cells situated 

 in the spinal cord. And, as we shall see, the condition described 

 in the paper on retrograde degeneration, namely, the presence of 



