426 BIOLOGICAL EFFECTS OF RADIATION 



was no such abundant mitosis in the cells of the parenchyma. At 24 hr. 

 there was no beginning of a cap of regeneration cells at the cut surface, 

 and abnormal mitoses were numerous in the parenchyma while other parts 

 appeared normal. At 48 hr. it appeared that exposures longer than 

 30 min. had hindered cell division to such an extent that no cap of 

 regeneration cells was formed. Exposures up to 30 min. gave some abnor- 

 mal cell division but did not completely check the normal mitoses and 

 formation of the cap. In general the number of all mitoses, both normal 

 and abnormal, declined with increasing periods of exposure. Dediffer- 

 entiation was found in both irradiates and controls. It seemed not to be 

 influenced by the rays except as mitosis was involved. At 72 hr., with 

 the higher exposures, there was extensive cell degeneration in the paren- 

 chyma (Fig. 10). 



The worms cut 1 to 3 days after irradiation showed greater injury 

 to the tissue than those cut immediately after similar exposures. After 

 the shorter exposures abnormal mitoses persisted for a considerable time 

 with subsequent cell degeneration. With the longer exposures cell divi- 

 sion was lacking and degeneration had appeared 24 hr. after the cutting. 

 Pieces in stages of deformation showed local degeneration of the body 

 epithelium and a degeneration of the parenchyma as a result of the 

 destruction of the regenerative cells (Fig. 10). The deformation as 

 externally visible resulted from an accumulation of degenerating cell 

 material arising either from the cells injured by the rays or by sloughing 

 off of gut cells. Irradiated whole specimens appeared about the same as 

 those cut for regeneration, except that distention as a result of accumu- 

 lated material from the gut did not occur. In the degenerating areas 

 of the surface there were mitoses and also cell degeneration, with the 

 latter predominating in later stages. Brief study of the sex cells showed 

 the oocytes and spermatocytes in stages of degeneration 4 or 5 days after 

 irradiation. In general the changes appeared later in the more differ- 

 entiated sex cells than in the cells of the parenchyma and after longer 

 exposures. 



It was evident from the foregoing data that the histological changes 

 involved in the first instance the formative cells or those with embryonic 

 potencies, and that the obvious effect was upon mitosis in these cells. 

 The law of Bergonie and Tribondeau was thus again confirmed, and 

 Weigand thought he could distinguish as the primary effect upon mitosis 

 (cf. 1, 2) pycnosis along with the absence of mitoses that was found 

 during the first hours after exposure, and as the secondary effect the 

 abnormal mitoses that subsequently appeared. Since changes were thus 

 recognizable in the cells so soon after the irradiation, Weigand questioned 

 whether one could speak of a latent period in the morphological sense. 

 In attempting a more complete analysis of his observations, the changes 

 in the irradiates were correlated with the account of the normal histo- 



