gager: effect of radium rays on plant life 155 



more easily killed. If cancerous tissue is of embryonic nature, as 

 seems not improbable, then it should be possible to treat it with 

 success by exposure to the rays of any radioactive substance, 

 if the proper strength of the radiation and the suitable conditions 

 of exposure are accurately ascertained ; otherwise more harm than 

 good may result. 



Among a rather large number of investigations on this subject 

 may be mentioned that of Wood and Prime, ^ as one of the more 

 recent. These investigators found that 155 mgm. of radium 

 bromide, screened with i mm. of aluminum or with 0.8 mm. of 

 brass, and only about 1.5 mm. distant from beating embryonal 

 heart-tissue, does not kill it in 3 hrs., and does not stop the growth 

 of connective tissue cells. The same exposure, however, does 

 prevent the growth of Jensen rat-sarcoma, and inhibits, but does 

 not wholly prevent, the growth of the Flexner rat-sarcoma. 

 These observations are rightly held by the authors to emphasize 

 the danger of generalizing from a limited number of experiments. 



One of the members of the Pennsylvania Commission on the 

 Chestnut Blight consulted the writer some time ago on the probable 

 efhcacy of a solution of some radium-salt injected into the circu- 

 lation of the tree. Recalling that the fungus causing the chestnut 

 blight is largely confined to the cambium-layer, and also recalling 

 that the cambium is embryonic tissue, it is obvious that the in- 

 jection into a tree of any radioactive substance in sufficient quan- 

 tity to kill the fungal hyphae would also kill the cambium. The 

 cure would be more fatal than the disease. 



That a form of energy shown to be capable, under favorable 

 conditions, of doubling the rate of growth of plants, might have 

 great agricultural possibilities is a very alluring proposition, and 

 was early subjected to experimental test. An exhaustive review 

 of the literature is not essential here, but a few investigations 

 may be noted. 



Studies by Fabre^ indicate that the presence of radium bromide 

 in the soil retarded the germination and development of Linum 

 catharticum. 



In 1 91 2 Ewart^ using a radioactive mineral, known experi- 



1 Proc. Soc. Exp. Biol. Med. 11: 140-142. 20 My 1914. 



2 Compt. Rend. Soc. Biol. Paris 70: 419-420. 1911. 

 ^ Jour. Dept. Agr. Victoria 10: 417-421. 



