136 GEORGE FRED SUTHERLAND. 



following Statement : " Die unterste Theil des regenerirten Mediil- 

 larrohres beherbergt in seinem Innern lind zwischen seinen 

 Epithelzellen zahlreiche fettig degenerirende Leukocyten; viele 

 kleine und grosse Fetttropfen, die man hier iiberall findet, fiihre 

 ich ihrem Ursprunge nach auf solche zerfallene Wanderzellen 

 zuriick. Ausserdem finden sich hier auch viele Pigmentkorncheni 

 die wohl bei der regressiven Metamorphose der zerfallenden 

 Leukocyten entstehen (Pigmententartung)." 



Barfurth figures the spinal cord of a larva of Triton cristatus 

 after the sixth day of regeneration, in which these leucocytes and 

 fat drops are shown. His figure is very similar to Fig. 11, which 

 shows a section of a tadpole killed twenty-four hours after the 

 operation. Both Fraisse and Barfurth mention particularly the 

 presence of leucocytes in the early regeneration stages, but in 

 the present study, leucocytes were not found in large numbers. 

 Up to the end of the first day, none at all were seen close to the 

 spinal cord. The earliest stage mentioned by Barfurth is that 

 after a forty-six hour regeneration period, and this probably 

 accounts for the different interpretation he gives of the origin 

 of the "Fetttropfen" or fragments. If these fragments are 

 followed back into earlier stages in my sections, they become 

 larger and larger and are seen to be identical with the degenerating 

 nuclei. To be sure, the leucocytes when they first appear in the 

 spinal cord region contain what might be called fat drops, but 

 is it not more reasonable to suppose that the leucocytes which are 

 present at this time dispose of the fragments of injured spinal 

 cord nuclei? 



3. Temporary Closing of the Spinal Cord. 



Barfurth describes the closing of the spinal cord at three days 

 by means of cytoplasmic extensions of the cells, such as were 

 seen in the preparations used in the present study. "Der sich 

 wieder ansammelnde Liquor cerebrospinalis driickt nun auf die 

 neugebildeten, noch wenig resistenten untern und seitlichen Theile 

 des Rohres, und treibt sie kolbenartig auseinander. Die Zellen 

 passen sich einstweilen durch ihre Lagerung diesem Druck an 

 und behalten spater diese Lage noch eine Zeit lang bei." Bar- 

 furth mentions this as a temporary closure of the spinal cord, so 



