RADIANT ENERGY 411 



molds). The plasmodia of Myxomycetes radiated in culture 

 with radium needles (five 12-mg. needles in a 9-cm. dish) show no 

 harmful effects whatever but grow luxuriantly — often better 

 than the controls. While usually avoiding direct or constant 

 contact with the needles, the protoplasm may actually entwine 

 them for an hour or more at a time (Fig. 173). No suppressed 

 ill effect is to be observed in the future cultures of the radiated 

 material, nor does the protoplasm itself, under microscopic 

 examination, show any change. This is true only in culture 

 where the protoplasm of the mold can avoid close proximity to 

 the radium, but damage results when a small piece of Plasmodium 

 is kept within 1 mm. of the radium (nine needles totaling 108 mg.) 



Fig. 173. — The protoplasm of a slime mold entwining a 12-mg. radium needle. 



for long periods of time; however, the protoplasm continues 

 streaming for 3 hr. during treatment and may still be alive and 

 capable of renewed growth when removed to a culture medium 

 after 20 hr. of treatment. 



Animal cells usually react unfavorably to radium radiation, 

 but the extent of the reaction is dependent upon other factors. 

 Both Packard, on Drosophila eggs, and Strangeways and Fell, 

 on chick tissue cultures, found that if two lots of cells are radiated, 

 one at a high and one at a low temperature, the death rate is 

 much greater in the former (owing to greater metabolic activity). 



The use of radium rivals that of X rays in medical therapy. 

 Of the three types of radiation, gamma rays are the most effective, 

 though beta particles are sometimes used. Gamma rays serve 

 the surgeon in the treatment of cancer. Beneficial results have 

 undoubtedly been obtained from the use of radium, but the bene- 

 fit has not been so great or so permanent as had been hoped. 



