388 Junnial of Comparative Neurology and Psychology. 



The degeneration wliich is seen beginning in certain fibers 45 

 days after the lesion is, therefore, a process commencing after 

 the orthnary secondiuy degeneration is complete. Another 

 feature which distinguishes retrograde degeneration from sec- 

 ondary degeneration is the fact that the latter occurs simul- 

 taneously throughout the entire length of the severed part, 

 while the former may involve only a small part of a fiber in the " 

 innnediate vicinity of the lesion. 



A word may be said regarding the nature and cause of 

 this degeneration of the proximal part of injured fibers. Van 

 Gkhuciiten (4) has shown that associated with these changes 

 in the fiber leading to its disintegration, there is a chromatolysis 

 of the cells of origin resulting, in certain cases, in their complete 

 destruction. In those neurones in which this occurs he believes 

 that the degeneration of the fiber follows on the death of the 

 cell and proceeds down the fiber toward its terminals. I'"or 

 this reason, he objects to the use of the term "retrograde" in 

 designating this type of degeneration, because it indicates that 

 the degeneration begins at the i)oint of injury and proceeds to- 

 ward the cell body. 



It is, however, quite conceivable that the evidence ot this 

 disintegration of the neurone sliould be found first in the i)or- 

 tion of the neurone farthest separated from the nucleus, namely 

 at the tip of the fiber near the lesion. As a matter ol fact 

 many of the pre[)arations upon which this paper is based show 

 a degeneration in the end near the lesion while the rest of the 

 fiber a[)pears normal. In some cases beginning near the lesion 

 and tracing the fiber toward the cell of origin one may see all 

 the stages of degeneration ; at first the fiber stains faintly be- 

 cause of the absorption of its myelin, then it is found to be well 

 stained but of irregular contour and finally it takes on a i)er- 

 fectly normal appearance. It seems clear, therefore, that in 

 this case at least the process is a true retrograde or cellulipetal 

 defieneration. 



