1. Penrose, L., and Quastel, J. H., Biochem. J., 31, 266 (1937).
2. Fischer, E., and Ach, F., Ann., 253, 57 (1889).
3. Briggs, A. P., J. Biol. Chem., 51, 453 (1922).
4. Datta, S. P., Harris, H., and Rees, K. R., Biochem. J., 46, xxxvi (1950).
5. Datta, S. P., Harris, H., and Rees, K. R. (private communication).