1. Stumpf, P. K., J. Biol. Chem., 169, 367 (1947). Dische, Z., Proc. Soc. Exp. Biol. and Med., 55, 217 (1944).
2. Friedkin, M., and Kalckar, M., J. Biol. Chem., 184, 437 (1950).
3. Cori, G. T., Slein, M. W., and Cori, C. F., J. Biol. Chem., 173, 605 (1948).
4. The crude mixture of deoxynucleotides was obtained by precipitation of an enzymatic digest of deoxypentose nucleic acid by lead acetate according to Klein, W., in “Methoden der Fermentforschung”, 1 (1941).
5. Volkin, E., Khym, J. X., and Cohn, W. E., J. Amer. Chem. Soc. (in the press). A preparation of barium adenylate was generously supplied by Dr. W. E. Cohn.