400 BIOLOGICAL EFFECTS OF RADIATION 



degeneration which is characterized by severe nuclear changes among 

 the cells in the resting state; and finally a period of remarkable regenera- 

 tion and recovery which results in a return of the tissue to its normal 

 condition. 



Except for the work on the neural tube, few detailed observations 

 have been made on the effects of carefully controlled nonlethal doses of 

 radiation on other tissues of the embryonic chick. However, observations 

 by Col well, Gladstone and Wakeley (30, 31) show that changes take place 

 in probably every one of the embryonic tissues after radiation. A study 

 of the nature of these alterations in each tissue and a determination so 

 far as possible of the factors which govern them offer an attractive field 

 for future investigation. 



It has long been known from clinical observation and from experi- 

 mental evidence that the radiation of pregnant mammals, either with 

 radium or with X-rays, may seriously affect fetal development. The 

 reports dealing with this subject, however, are for the most part of a very 

 general nature and are scattered through biological and clinical literature. 

 For more complete references than will be given here to the work in this 

 field the reader is referred to the paper by Bailey and Bagg (14). 



By far the most complete and systematic work on the effect of radia- 

 tion on fetal development of mammals has been done by Bagg (9 to 12) 

 and his collaborators. Bagg has treated breeding female mice and rats 

 with radium and with X-rays before and after mating, and also in late 

 stages of pregnancy. His results show that when females after mating 

 are injected subcutaneously with radioactive physiological salt solution, 

 the formation of embryos is in many cases prevented. In other cases 

 Bagg found that development began, but the embryos were either 

 absorbed in utero or early abortion took place. In still other cases, 

 abnormal young were born alive at term. The abnormalities which such 

 offspring exhibited were principally serious vascular disturbances. 

 There was a breakdown of capillary endothelium and the formation of 

 prominent subcutaneous hemorrhagic areas. In general, these vascular 

 disturbances appear to be of the same type as those which have been 

 observed in radiated chick embryos by Strangeways and Fell (88) and 

 other investigators. 



Bagg found that hijection of female mammals with radioactive salt 

 solution before mating, instead of after mating, resulted in less dis- 

 turbance of fetal development. However, in some cases the absorption 

 of embryos or early abortion occurred, and in other cases the young 

 which were born alive at term exhibited the characteristic subcutaneous 

 hemorrhagic areas. 



Bagg has also used the method of exposing the ventral abdominal wall 

 of pregnant mammals, which were nearly at full term, to the action of the 

 gamma rays of radium. This treatment resulted in the production of 



