82 



MARY ELMORE SAUER AND DONALD DUNCAN 



This behavior furnishes a means of distinguishing, on the basis of the Feul- 

 gen-positive granules, between death of mitotic and of interphase stages. The 

 granules become cytoplasmic when resorbed by a neighboring cell. 



In Fig. 1, based on the neural tube of the irradiated tadpole during the 

 prolonged prophase extending from 11 to 24 hours, the low metaphase count 

 means that heavy casualties occur on completing prophase. These casualties 



5 ^5 



V 



O 

 o 50 



o 

 S 25 



2 50 



« 25 



8 



40 



48 



16 24 32 



Hours after irradiation 

 MODIFIED FROM SPEAR & GLUCKSMANN, (1938) 



Fig. 1 . Chart showing the number of mitotic and degenerate cells in the brain and 

 retina of young tadpoles for 48 hours after exposure to gamma radiation (268 r). 



\. Mitosis. Key: prophase, ; metaphase, ; anaphase and telophase, 



Although prophases are normally fewer than metaphases, from 11 to 24 hours after 

 radiation the number of prophases greatly exceeds the number of metaphases, indi- 

 cating a prolongation of the prophase period. The subsequent decrease in the number 

 of prophases without change in the number of metaphases indicates degeneration of 

 many of the prophases. II. Degeneration: Three stages, as applied to the nucleus. 

 Stage A. Chromatopycnosis, . The chromatic material separates from the non- 

 chromatic, with the chromatin material appearing as scattered granules. Stage B. 



Hyperchromatosis of the nuclear membrane, . The chromatin granules have 



united into a single, deeply staining mass sitting as a cap on the nuclear membrane. 



Stage C. Chromatolysis, The chromatin breaks into fragments, and loses its 



Feulgen staining properties. 



Since the mechanism of prophase effects separation of chromatic from non-chromatic 

 material, a cell which reaches prophase before degenerating omits the first stage and 

 passes directly into hyperchromatosis. The high increase in hyperchromatosis, be- 

 ginning shortly after the peak of the prophase curve, indicates that the greatest num- 

 ber of casualties occurs after the cell reaches prophase. (Modified from Spear and 

 Gliicksmann) . 



