46 PREVIOUS INVESTIGATIONS UPON ANIMALS 



Radium rays were found by Schwartz ^* to affect the yolk of eggs 

 more than the albumin. He considered that the rays decomposed 

 the lecithin of the yolk, and that they affect all^tissues in the same 

 way, for cells rich in lecithin, he says, are the most sensitive to the 

 rays. On the contrary Neuberg *^ concluded from his experiments 

 that the rays can decompose neither pure lecithin nor proteins, and 

 probably do not decompose them within the cell. 



In 1904 von Baeyer^ found that both the alpha and the more 

 penetrating rays from radioactive lead, polonium, and induced sil- 

 ver and palladium cause the death of bacteria, but that the alpha rays 

 do not affect the skin. He holds the opinion of Scholtz that the 

 effect on the skin is to be ascribed to the penetrating rays. 



The effect of Rontgen rays on regeneration in planarians was in- 

 vestigated by Bardeen and Baetjer.'' Their experiments showed 

 that cell-division may be retarded and entirely stopped by a sufficient 

 exposure to the rays. They also noted that the effects did not appear 

 for some days after the first exposure, and that the rays have an 

 effect, not so much upon tissue differentiation, as upon cell reproduc- 

 tion. The rays were found to affect primarily cells possessing repro- 

 ductive capacity, and the authors suggest that "death in exposed 

 specimens may possibly be due to a necessity on the part of the 

 organism for a certain amount of cell-reproduction." 



The physiological effects of the radium emanation were studied 

 by Bouchard, Curie, and Balthazard,^^ and it was found to kill guinea 

 pigs and mice within one or two hours, according to the quantity of 

 the emanation used. The effect was shown not to be due to ozone 

 produced by the radioactivity of the emanation. 



In 1904 Caspari ^^ reviewed the physiological investigations with 

 the rays of radioactive substances since Becquerel announced the 

 discovery of Becquerel rays, and in the same year Danysz ^^ observed 

 that the epithelial tissues of young animals were more sensitive to 

 these rays than those of adults. 



According to Dorn and Wallstabe,^^ rabbits were not affected by 

 drinking tap-water which had absorbed the emanation, but were 

 poisoned by an exposure of one and one half weeks to air which con- 

 tained it. Their lungs Avere found to be hyperemic. 



Dunham "^ observed that Chilomonas and two species of Para- 

 tnoecmm were killed by six exposures of three minutes each to X rays 

 on three successive days, while rotifers, Arcella, and Cryptomonas 

 were not affected by that treatment. 



