1. The Edsel B. Ford Institute for Medical Research, Detroit, Michigan
2. The Department of Experimental Pathology, University of Havana School of Medicine, Havana, Cuba
3. Commission for the Prophylaxis of Syphilis, Leprosy and Cutaneous Diseases, Havana, Cuba
4. Institute of Health and Tropical Disease, Mexico, D.F.
5. Government Medical Service, Kingston, Jamaica, B.W.I.