1. Medical Research Center, Brookhaven National Laboratory, Upton, N. Y.
2. South African Atomic Energy Board, Pretoria, South Africa Research Collaborator, Medical Research Center, Brookhaven National Laborato-ry, Upton, N. Y.
3. Division of Experimental Pathology, Medical Research Center, Brookhaven National Laboratory, Upton, N. Y.
4. Medical Research Center, Brookhaven National Laboratory, Upton, N. Y. Present address: University of Minnesota, College of Veterinary Medicine, St. Paul, Minn.