1. United States Department of Agriculture, Beltsville, Md., and the Department of Microbiology, University of Maryland, College Park, Md.
2. National Communicable Disease Center, Atlanta, George.
3. Pioneering Blood Antigen Lab., Animal Husbandry Div., U. S. Dept. of Agriculture, Beltsville, Maryland.
4. Department of Microbiology, University of Maryland, College Park, Maryland.