lissauer's tract in the cat 265 



intact. He admits the contention of Nageotte that such degen- 

 eration as he finds may be tertiary, but insists that one cannot 

 be certain that the tract does not contain some fibers from the 

 posterior roots. 



Sibehus ('05), who studied three cases in which the cauda 

 equina was involved, found some degeneration in Lissauer's tract 

 which he considers as the direct result of the root lesion. He 

 explains the negative findings of Nageotte by assuming that the 

 fine horizontal fibers of Lissauer's tract had disappeared and that 

 the author had failed to notice their absence. This explanation 

 is tantamount to an admission that the proportion of dorsal root 

 fibers in the tract is small and that they are chiefly horizontal. 



Sottas ('93) and Collier and Buzzard ('03) find a limited amount 

 of degeneration in Lissauer's tract after dorsal root lesion. 



The evidence seems to show that the medullated fibers in the 

 tract of Lissauer are in part endogenous and in part exogenous 

 and that the endogenous fibers predominate. We shall return to 

 this question again in discussing the entrance of the dorsal root 

 fibers into the spinal cord. 



Pyridine-silver preparations. In pyridine-silver preparations the 

 tract of Lissauer is stained very dark and is even more sharply 

 outlined from the rest of the cord than in the Pal-Weigert prep- 

 arations. It is seen to consist of vertically or obliquely coursing 

 axons of the smallest diameter (fig. 2, 6). These are stained a 

 brownish black and are very sharply differentiated from the 

 almost colorless background. They are very closely set together, 

 although there are scattered among them a few medium sized 

 yellowish brown axons which correspond in number and arrange- 

 ment to the medullated fibers seen in the Pal-Weigert prepara- 

 tions. When compared with Pal-Weigert preparations of the 

 same segment of the cord the contrast is very striking. In the 

 latter the tract of Lissauer is very lightly stained and is seen to 

 consist of rather sparsely scattered fine medullated fibers. A 

 glance at the two preparations is sufficient to show that the 

 number of axons in the one is several times greater than the 

 number of myelin sheaths in the other. Lissauer's tract consists 

 then in part of small medullated fibers but its chief and charac- 



