 toxic sulfur-35 selenium tellurium avian embryo continu intern irradi chick embryo sulfur-35 administ 4th 8th dai incub produc abnorm observ selenium toxicosi avian embryo highest level sulfur-35 1600 uc inject egg 4-dai embryo produc morpholog abnorm sever produc level radiosulfur administ 8-dai embryo level stabl selenium toler selenium level greater 30 ug kill embryo 24 hour inject 20 time tellurium selenium requir kill embryo 24 hour abnorm observ tellurium-inject embryo 