KANEMATSU SUGIURA AND GIOACCHINO FAILLA 435 



induced, it was permanent. Furthermore, those mice which were not 

 rendered sterile by radiation were, as far as the experiments enable us 

 to say, as prolific as the controls. Remembering that a dose of 1.9 

 millicurie hours had no apparent effect on the ovaries, while a shghtly 

 larger dose, 2.4 millicurie hours, caused permanent sterility, it might 

 be concluded that it is not possible to produce temporary sterility by 

 radiation. We know, however, that temporary sterility can be 

 produced, at least when the animals are radiated at a later stage in 

 their development. The mice in our experiments were radiated for 

 the first time soon after birth, and it is not improbable that under 

 these conditions temporary sterility cannot be obtained. 



Large sublethal doses produced severe skin burns, retarded the body 

 growth of the animals, but failed to steriHze the males. About one- 

 third of the total skin area of the mice showed marked effects from the 

 radiation. The animals were very sick for a time, and their growth 

 was temporarily stunted. But nevertheless they recovered and finally 

 became apparently normal except for the narrow hairless strip of skin 

 which had been closest to the emanation tube. Only the females were 

 rendered permanently sterile. The males did not show even temporary 

 sterility when the doses of radiation were close to the lethal dose. 

 While the testes of mammals are known to be very easily affected by 

 radiation, still they are more resistant than the ovaries. In addition, 

 in these experiments they were at a greater distance from the source of 

 radiation than the ovaries, and they were better protected by the 

 thicker layer of tissue in the path of the rays. The fact that no sub- 

 lethal dose in these experiments sterilized the males shows that under 

 the conditions of irradiation adopted the amount of radiation reaching 

 the testes was not sufficient to affect them noticeably. If the source 

 of radiation had been applied closer to the reproductive organs of the 

 males, they would have been sterilized by millicurie hour doses much 

 smaller than the lethal dose. 



Some of the radiated animals were killed with ether, and macro- 

 scopic and microscopic examinations of the reproductive organs were 

 made. The ovaries of the sterile females were generally atrophied and 

 colored yellow. The normal histological structure was altered. The 

 characteristic findings were the destruction of the Graafian follicles, 



