866 RADIATION BIOLOGY 



In view of recent results to be discussed in more detail, it is of interest 

 to extract from the literature what information is available as to the stage 

 in gestation when death occurs. In five investigations (Burckhard, 

 Parkes, Russell, de Nobele and Lams, Driessen), in which the uterus was 

 examined within two weeks after irradiation, there is mention of finding 

 no signs of pregnancy in several of the females. This means either that 

 death occurred before implantation or that fertilization failed to occur. 

 Radiation was not administered early enough in any of the experiments 

 to have interfered with fertilization, although Burckhard (who began his 

 treatments earlier than most investigators) suggests that killing of sperm 

 in the female is responsible for nonpregnancy. Since a certain proportion 

 of matings is apparently always nonfertile, the early experiments, which 

 lack adequate controls for the determination of this proportion, provide 

 only suggestive evidence of preimplantation death due to early irradia- 

 tion. Somewhat more direct evidence comes from Kosaka (1928c) who 

 opened, within 72 hours after irradiation, three of fourteen guinea pig 

 females irradiated during the first week after conception and found dis- 

 turbances in implantation of embryos that had died earlier. Burckhard 

 (1905) reports retarded cleavage, which may be an indication of disturb- 

 ances leading to later death, some of it conceivably before implantation. 

 Finally, there are reports (Trillmich, 1910; Parkes, 1927) of finding no 

 sign of pregnancy externally, although here there also exists the possibility 

 of early postimplantation death. 



Ample evidence for death after implantation is presented by all investi- 

 gators except Burckhard, whose observations do not extend far enough 

 into that period. The usual finding consists of resorbing bodies or 

 decidual rests in the uterus, but two authors (Trillmich, 1910; Parkes, 

 1927) also mention abortion in later stages of pregnancy. A few reports 

 of arrested development (de Nobele and Lams, 1925; Driessen, 1924), are 

 probably to be classed with more obvious cases of resorption, since there 

 are indications that the embryos may have died shortly before 

 observation. 



Following up the indications of the survey experiment (Russell, 1950) 

 in which irradiation during preimplantation stages had reduced the 

 number of litters at term (see Table 13-3), as well as the litter size in 

 surviving litters (see Table 13-4), Russell and Russell (1950a) irradiated 

 a separate extensive series of females }4, ^ X A, ^hz, 3H, or 4^ days after 

 mating. A control was handled simultaneously with each irradiated 

 female. In an attempt to determine at what stages preimplantation 

 death occurred and whether any abnormalities were expressed in animals 

 thus weeded out before term, all uteri were examined either 10^2 or 13^2 

 days after mating, i.e., 6-13 days after irradiation. It was found that 

 radiation-induced death was considerable and that, in over-all effect, the 



