300 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 5 



stituted they immediately recognized the difference and ate vora- 

 ciously,^ Other experimenters have reported a similar disinclina- 

 tion to eat selenium-containing materials on the part of larger 

 animals as well as of rats (Franke, 1934; Munsell). 



The higher animals are not the only creatures that show extraor- 

 dinary sensitiveness to traces of selenium. Eed spiders are reported 

 to be very susceptible to selenium-containing insecticides. The 

 aphids or plant lice that infested the healthy wheat in some of my 

 experiments were never observed on those plants that were visibly 

 injured by selenium. When selenium was supplied to the roots of 

 plants already infested, the plant lice left. The number of aphids 

 on the plants varied so consistently with the amount of selenium in 

 the nutrient solution as to suggest that they might indicate the 

 relative amounts of selenium in the plants with an accuracy com- 

 parable to that of chemical analyses. It is interesting that algae 

 grew well in the solutions nourishing the plants on which the plant 

 lice died; and wheat mildew {Erysifhe graminis) and smut {Til- 

 letia tritici) attacked wheat plants containing relatively large 

 amounts of selenium (several hundred parts per million). 



Whether man is susceptible to ills attendant upon a selenium-con- 

 taining diet is not known. There have been occasional reports of 

 abnormalities of human beings in the seleniferous areas suggestive 

 of the symptoms of the poisoning in animals. But probably the 

 danger is slight, especially outside the affected areas, because of the 

 diversity of the normal human diet. 



LITERATURE CITED 



Beath, O. A., Draize, J. H., Eppson, H. F., Gilbeet, C. S., and McCke^vry, O. C. 

 1934. Certain poisonous plants of Wyoming activated by selenium and their 

 association witli respect to soil types. Journ. Amer. Pharm. Assoc, 

 vol. 23, pp. 94-97. 

 Beath, O. A., Dkaize, J. H., and Gilbeet, C. S. 



1934. Plants poisonous to livestock. Wyoming Agr. Exp. Stat. Bull. 200. 

 Byers, Horace G. 



1935. Selenium occurrence in certain soils in the United States with a dis- 



cussion of related topics. U. S. Dept. Agr. Techn. Bull. 482. 

 Cameron, Charles A. 



1880. Preliminary note on the absorption of selenium by plants. Sci. Proc. 

 Roy. Dublin Soc, vol. 2 (n. s.), pp. 231-233. 

 Draize, J. H., and Beath, O. A. 



1935. Observations on the pathology of blind staggers and alkali disease. 

 Journ. Amer. Vet. Med. Assoc, vol. 86, pp. 753-763. 

 Evans, A. T., Bushey. A. L., and Kuhlman, A. H. 



1925. [Unpublished report in files of S. Dak. Agr. Exp. Stat, and U. S. 

 Dept. Agr.] 



* These feeding tests were conducted under the direction of Dr. H. E. Munsell, TJ. S. 

 Bureau of Home Economics. 



