* This res/arch was supported by a grant from The Commonwealth Fund, Grant No. H2042(C3) from the National Heart Institute, aada grant from the National Science Foundation. 1 Fisher, H. F., E. E. Conn, B. Vennesland, and F. H. Westheimer, J. Biol. Chem., 202, 687 (1953). 2 Hoewus, F. A., F. H. Westheimer, and B. Vennesland, J. Am. Chem. Soc., 75, 5018 (1953). ' Singer, T. P., and E. B. Kearney, J. Biol. Chem., 183, 409 (1950). 4Commoner, B., and B. B. Lippincott, these PROCEEDINGS, 44, 1110 (1958). 6 Isenberg, I., and A. Szent-Gybrgyi, these PROCEEDINGS 45, 1229 (1959). 6 Isenberg, I., and A. Szent-Gybrgyi, these PROCEEDINGS, 46, 1307 (1960).