44 PREVIOUS INVESTIGATIONS UPON ANIMALS 



after two or three weeks, a strong irritation with pigmentation, and 

 finally a peeling off of the skin, followed soon thereafter by healing. 

 Rutherford *" describes an inflammation that lasts from lo to 20 days, 

 after which the skin peels off, while the pain endures for two months. 

 He states that these results are due mainly to the a and /9 rays. 

 Becquerel and Curie ^ obtained the burns with a preparation of only 

 800,000 activity, and found that the effect varied with the intensity 

 of the active rays and the duration of the exposure. Personally I 

 have never experienced any inconvenience in handling sealed glass 

 tubes of radium bromide of activity as high as 1,800,000, though I 

 have never taken any special care to avoid injury, I have carried 

 a wooden, velvet-lined case containing the preparation in my vest 

 pocket for several hours, and in my ungloved hand for as long as 

 half an hour, without ever having experienced any " burning " or 

 other unpleasant effects. 



Joseph and Prowazek,'^^ exposing Paramoecia and Dafhnia to X 

 rays, found that those organisms show a negative tropism with refer- 

 ence to the ra3^s. The plasm of Parmnoecia and Bryopsis undergoes 

 modifications which were interpreted to signify either injury or 

 exhaustion. 



In much of the literature, especially the earlier, the amount of 

 radium used and its activity are not given. Bohn ^ found that 

 embryos of Bujo vulgaris grew more slowly after exposure to the 

 rays of radium, and exposed tadpoles of the frog developed into 

 monstrosities. He also says that if the rays of radium act upon the 

 body of an animal for several hours, the tissues acquire new proper- 

 ties, which may remain in the latent state for a long period, but 

 manifest themselves as soon as the normal activity of the tissues is 

 resumed. The activity of his preparations is not given. 



In a later paper Bohn^" states that if sea-urchins [Strongylocen- 

 trotus lividiis) are exposed for from 20 minutes to 2 hours after 

 gastrulation, the plutei are small and atrophied. The rays rapidly 

 enfeeble or kill spermatozoids, but, on the contrary, eggs submitted 

 to their influence seem to become more susceptible of being fecun- 

 dated, and are increased in vitality. The rays affect the nuclear 

 chromatin especially, increasing its activity or destroying it, accord- 

 ing to the duration of exposure. Spermatozoids are more sensitive 

 than ova, because they consist of almost naked chromatin, but the 

 chromatin of eggs, protected by the cytoplasm, is so stimulated, he 



