48 PREVIOUS INVESTIGATIONS UPON ANIMALS 



prolonged. In 1905 Bongiovanni " also announced to the Bologna 

 Academy that radium rays rapidly destroy the virus of rabies, both in 

 tubes and when applied to animals, within an hour of their infection. 

 "Animals already suffering could be cured with certain results." 

 Danysz * was unable to reproduce the results of Tizzoni and Bon- 

 giovanni. 



According to Schaper,*^ an exposure to radium rays retarded and 

 modified the regeneration of the tail in Triton larvae, and regener- 

 ation of Planaria luguhris was similarly affected by an exposure of 

 three and one half hours to the rays, and of 5 mm. -larvae of Rana 

 esculenta by the emanation. Cell-division, embryonal differentia- 

 tion, and growth were inhibited after a longer or shorter latent period. 

 Eggs of Rana esculenta^ exposed at various stages of segmentation 

 or early differentiation of the embryo, were retarded in development, 

 and the embryos were small and deformed. 



The destruction of the activity of chymosin by radium rays was 

 attributed by Schmidt-Nillsen ^^' ^^ to the ultra-violet rays caused by the 

 phosphorus in his preparations. When Venenziani^^ placed speci- 

 mens of Opalina ranarnni (a ciliated parasite, living in the intestinal 

 fluid of frogs) in a 5 per cent, sodium chloride solution, and then ex- 

 posed them to rays from o. i gm. of radium salt of 10,000 activity, they 

 lived longer than control specimens, similarly placed, but not exposed 

 to the rays. In water the exposed organisms survived still longer. 



Willcock^' found that Etiglena vh-tdis manifested no tendency to 

 avoid or to accumulate in the path of rays from barium, but Jen- 

 nings'^' had already found it almost impossible to obtain any directive 

 response to other stimuli from Etiglena. The barium rays seemed 

 to hasten spore formation in small encysted forms, and encysted forms 

 of the larger variety were made active by 24 hours' exposure to the 

 rays from 5 mg. of radium bromide. Stentor viridis contracts 

 when the rays fall upon it. Repeated exposure results in a marked 

 decrease in irritability and in the capacity for contraction and exten- 

 sion. Hydra Jtisca^ which contains no chlorophyll, gave no tropostic 

 response, even during exposures that resulted in death, but Hydra 

 viridis, which contains a green algal symbiont, does manifest a nega- 

 tive radiotaxis which decreases with fatigue, as with Stentor. The 

 response takes place both in full daylight and in absolute darkness. 

 An exposure of two hours to «, /9, and /rays acting together caused 

 Hydra fusca to disintegrate, and the result was attributed to the effect 



*Ann. Inst. Pasteur 20: 206. 1906. 



