NUCLEAR CHANGES IN RANA CLAMITANS. 



129 



2. Enlargement of Nuclei. 



A few preparations of the spinal cord soon after the operation 

 show plainly that the nuclei near the end, but just in front of the 

 deeply-staining nuclei, are larger than those of the normal cord. 

 The long axes of nuclei close to the edge were measured and com- 

 pared to nuclei of the same preparation which are some distance 

 forward in the old tissue (Table I.). Immediately after the 



Table I. 



Time of Regeneration. 



Nuclear Length 

 Close to Edge. 



Nuclear Length 

 in Front of Edge. 



Difference in 

 Length. 



Normal 



Immediately . 



I hour 



3 hours 



5.5 hours. . . , 

 9.5 hours. . . , 

 14 hours. ... 



1 day 



2 days 



3 days 



4 days 



6 days 



7-9 

 [0.5 



"•3 

 8.6 



C2.8 



8.1 

 7-6 

 8.2 

 8.1 

 8.2 

 8.4 

 [0.7 



7-5 

 7.8 

 9.1 

 7-3 



lo.s 

 8.0 

 8.3 

 6.6 

 8.0 

 8.9 

 8.2 



10.4 



•4 

 2.7 

 2.2 

 1-3 

 2.3 



.1 



-•7 



1.6 



.1 



-•7 



Explanation. — Each measurement recorded here is the average of the measure- 

 ments of 9 or 10 nuclei. These were recorded in terms of the spaces of the ocular 

 micrometer, but since one space was equal to approximately one micron (.955), 

 the measurements were not transposed. 



operation and in the very early regeneration stages, the nuclei 

 near the end are larger, but the difference decreases until after 

 nine and a half hours it is hardly significant. This enlargement 

 might be preparatory to normal division or it might be a swelling 

 which is a degenerative change preliminary to fragmentation 

 Since this size difference is greatest at the very beginning and 

 decreases during the first day until it is no longer significant, and 

 since mitotic divisions are not seen in numbers until the third 

 day, the enlargement is probably an early stage in nuclear 

 degeneration. 



3. Temporary Partial Closing of the Spinal Cord. 



After the degenerative process is complete and the deeply- 

 staining nuclei have disappeared, the end of the nerve cord starts 

 to close over. By the first day, the nuclei in the end of the cord 



