KANEMATSU SUGIURA AND GIOACCHINO FAILLA 431 



cases the doses of radiation which caused sterility either are not given 

 at all or they are given incompletely. The marked response to radia- 

 tion which the reproductive cells exhibit can be explained by Bergonie 

 and Tribondeau's generaHzation, already referred to. In the experi- 

 ments of this paper, the effect of radiation on the reproductivity of the 

 mice was also investigated. For this purpose the radiated animals 

 were mated with normal mice about the 35th day after birth. One 

 radiated male was mated with two normal females of about the same 

 age. The animals were kept in the same cage until both females 

 had produced at least three Utters of young. Two radiated females 

 were mated with two normal males, and they were not separated until 

 the females had reached the age at which they normally cease to 

 breed. In general, the young were separated from the mother soon 

 after birth. In the case of the mice of Experiments 1 and 4 the young 

 of one litter in either experiment were allowed to remain with their 

 mother until weaned. These mice and succeeding generations were 

 kept under observation to determine whether radiation affected the 

 offspring of the radiated mice. 



The results of the breeding tests were as follows: All the males of 

 Experiments 1 to 7, receiving doses of 1.9 to 26.8 millicurie hours, were 

 fertile. (Those of Experiments 8 and 9 succumbed to doses of radia- 

 tion larger than 26.8 millicurie hours before they reached sexual 

 maturity.) On the other hand, with the exception of the mice of 

 Experiments 1 to 4, all the radiated females were rendered permanently 

 sterile. Those of Experiments 1 and 4 were fertile. Tliis shows that 

 a dose of 1.9 millicurie hours (Experiment 1) applied as already 

 explained (Table I) was not sufficient to sterilize female white mice. 

 However, with one exception (Experiment 4) larger doses were effec- 

 tive. The apparent anomaly when a dose of 6.8 millicurie hours was 

 used (Experiment 4) is due to the fact that in this case the emanation 

 tubes were placed directly over the heads of the animals (Table I). 

 Thus the ovaries were at a greater distance from the radioactive source, 

 and they also were better protected from the radiation by a greater 

 thickness of tissue in the path of the rays. In Experiment 6, the dose, 

 21.9 millicurie hours, was sufficient to cause sterilization, even though 



bondeau, L., and Recamier, D., Compl. rend. Soc. bioL, 1905, xii, pt. 1, 284. 

 Brown, T., and Osgood, A. T., Am. J. Surg., 1904-05, xviii, 179. 



