City, for a sample of his plasma lipid fraction. For small quantities of human serum albumin, we are indebted to Dr. John Edsall of the Department of Physical Chemistry, Harvard Medical School. Human blood serum from negative Wassermann tests was made available to us through the kindness of Mr. J. H. Spooner of the State Department of Health, Trenton, New Jersey. We are grateful to Dr. Garth Johnson for his generous counsel and encouragement in this investigation.