PREVIOUS INVESTIGATIONS UPON ANIMALS 49 



on the nervous system of the oral disc, for this was the region first 

 affected, and no response at all was obtained when the foot was ex- 

 posed. Opalina, JVyctothet'us, and Balantidium^ organisms without 

 chlorophyll, suffered no obvious harm, and manifested no response 

 when exposed for 24 hours to rays from 50 mg. of radium bromide, 

 though these organisms are very sensitive to ordinary stimuli. Nega- 

 tive results were also obtained with Actinosphaerimn and rotifers. 

 Thus, only forms containing chlorophyll appeared to be sufficiently 

 sensitive to the rays to react, and the author suggests that the green 

 algae, living symbiotically with Hydra viridis and Stcntor, act as 

 sense organs for the beta rays, possibly through a modification of the 

 metabolism of the alga by the rays, and a consequent disturbance 

 of the balance between the two organisms. This author's brief note 

 on experiments with plants is referred to on page 62. 



In harmony with an inference of Willcock with reference \o Hydra, 

 is the result of Beck,^ who found that radium rays either deaden or 

 destroy the sensibilities of the peripheral nerves. In the same year 

 (1905) Salomonson and Dryer ^^ stated that rays from 5 mg. of 

 "pure" radium bromide, passing through a sheet of mica, had little 

 effect on the protozoan JVassula, even after six days. Some speci- 

 mens of amoebae were killed in twelve hours, while others survived 

 for four days. Trypanosoma Brucei wdLS killed in from two to three 

 hours, and on red blood corpuscles the rays exerted a haemolytic 

 power. 



Hewlett-^ has suggested that the inhibition of cancerous growth 

 by radium and X rays may be because the rays cause proliferation of 

 the connective tissue elements of the growth, and thus interfere with 

 its nutrition. ♦' It is possible," he further says, " that the stimulus of 

 these rays may also act like fertilization, and cause the gametoid 

 once more to revert to the somatic cells." No experimental evi- 

 dence, however, is adduced in support of either of these hypotheses. 



A thorough study of the effects of radium rays on chlorophyllous 

 and non-chlorophyllous organisms was made in 1905 by Dr. Margaret 

 Zuelzer."- She exposed large numbers of Spirostemum ambigiium 

 and the chlorophyll-containing Paramoecium barsaria to the rays, and 

 found that, after 24 hours' exposure, from four to seven out of ten 

 Paramoecia had divided, but not so in the case of the Spirostema. 

 Cell-division of the chlorophyll-containing Paramoecia had ceased 

 after 30 hours of exposure. The animals which had not been notice- 

 5 



