The research reported in this book on the metabolism during pro longed fasting is a continuation and amplification of the investiga tions reported in The in?uence of inanition on metabolism (carnegie Institution of Washington Publication No. 77, The opportunity to conduct this series of scientific observations on a man living for 31 days without food and drinking only distilled water would have been of little value without the cooperation of a large number of scientific associates and computers. Certain co-workers kindly assumed the responsibility not only for the accumulation of the data but also for the preparation of a report of their respective findings. In this book special reports are made by Dr. H. W. Goodall on the physical condition of the subject during the fast, his subjective impres sions and mental attitude toward the fast, and the microscopy of the urine and the tests for albumin; by Dr. J. E. Ash on the blood; by Dr. H. S. Langfeld on the psycho-physiology of the fast; by Dr. A. I. Kendall on bacterial intestinal ?ora; and by Mr. H. L. Higgins on alveolar air.