Toxicity of selenium-cystine and some other organic selenium compounds**The author wishes to thank Dr. Arne Fredga of Uppsala University, Uppsala, Sweden, for the generous supply of selenium-cystine and other organic selenium compounds, and Dr. C. A. Elvehjem, Dept. of Agricultural Biochemistry, University of Wisconsin, for courtesies and helpful suggestions during the course of the work. The work reported herein was done in the laboratories of the Department of Agricultural Biochemistry, University of Wisconsin, during a leave of absence from the South Dakota State College.