126 



Messrs. H. O. Feiss and W. Cramer. [Oct. 22, 



lower ligature showed characteristic signs of a nerve degenerated for five days, 

 while preparations from the segment between the ligatures showed the 

 peculiar flaky appearance of the myelin that was seen in nerves kept in 

 Einger's solution. The contrast in the appearance of the two preparations 

 was very marked, although the amount of breaking up of the myelin was 

 about equal in the two segments. (See Plate 4, figs. 2 and 3.) 



The difference obtained between the two segments in this experiment 

 suggested the possibility that the interference with the circulation might 

 have an effect on the onset of Marchi's reaction. In five cases the external 

 popliteal nerves were tied between the ligatures. The nerves were removed 

 after 8, 11, 12, 13, and 14 days respectively and the Marchi reaction in the 

 segment between the ties compared with that in the segment below the ties. 

 It need hardly be pointed out that by this method the circulation was not 

 cut off for the whole length of time during which degeneration took place. 



The 8- and 11-day specimens showed no Marchi reaction. The 12- and 13- 

 day specimens showed beginning Marchi reactions. In neither case was there 

 any appreciable difference between the segments compared. The 14- day 

 specimen showed a more positive Marchi reaction. Here again there was no 

 appreciable difference between the segments compared. 



Summary. 



Cats' nerves removed from the body and kept at body temperature in 

 Einger's solution or in blood serum exhibit certain changes in the myelin 

 sheath as studied in osmic acid preparations, which resemble the early changes 

 exhibited by nerves degenerated for about equal lengths of time in the living. 

 These changes are slowed but not inhibited by lower temperatures. In nerves 

 kept in liquid paraffin, the changes are not seen to occur to any great extent. 



There is one difference in the appearance of nerves degenerated in vivo 

 from that of nerves kept in vitro : the broken down myelin stains less clearly 

 in the latter condition, and thus has a flaky appearance. This same flaky 

 staining was noted in the living when the circulation of a nerve was cut off 

 locally. 



Nerves kept in Einger's solution in vitro showed no Marchi reaction and 

 no signs of nuclear activity. 



Conclusions. 



In discussing the nature of the changes comprised under the term 

 Wallerian degeneration, we must consider separately the proliferation of the 

 neurilemmal nuclei and the fragmentation of the myelin sheath. That the 

 former is a manifestation of life goes without saying. The fragmentation of 



