1. Department of Medicine, New York University School of Medicine, New York, N. Y.
2. New York University School of Medicine, New York, N. Y.
3. New York University School of Medicine, New York, N. Y.; Career Scientist of the Health Research Council of the City of New York.
4. New York University School of Medicine, New York, N. Y.; Career Scientist of the Health Research Council of the City of New York. Please address requests for reprints to Dr. R. Silber.