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RADIATION BIOLOGY 



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DAY IRRADIATED (POSTCONCEPTION) 



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Fig. 13-7. Visceral skeleton, viscera, and miscellaneous. 



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altogether, spread over a considerable portion of embryonic life. In 

 addition to skeletal abnormalities, changes noted on careful external 

 examination and on gross dissection were recorded. A large control 

 group (372 newborns) was studied in the same manner as 420 newborns 

 which had been irradiated during prenatal life. Since it is impossible to 

 give a complete report of changes observed (the checklist of characters 

 examined included about a hundred items), only the most striking ones 

 and those most useful for comparison with the results of other investi- 

 gators are represented in Figs. 13-4 to 13-7. These samples will serve to 

 illustrate the general type of result obtained. 



Almost all abnormalities represented in Figs. 13-4 to 13-7 were found in 

 newborns or fetuses at term but are projected back upon the stage at 

 which they were apparently induced. Width of the bands represents 

 percentage incidence at term. Without going into details about the 

 abnormalities, several general features of Russell's results may be pointed 

 out. First, it is striking that with the general survey dose of 200 r, 

 abnormalities in a high proportion of the animals are obtained only from 

 embryos exposed after day 5)^ (no external and visceral and only 2 per 

 cent slight skeletal abnormalities from irradiation of earlier periods). At 

 the other end, day 13^ is probably the limit beyond which abnormalities 

 of the types looked for at term can no longer be obtained with 200 r. 



