The structure of proteins; two hydrogen-bonded helical configurations of the polypeptide chain.

by an increase in protein content, while the amount of desoxyribonucleic acid remains unchanged. Acknowledgments.-This work was supported by research grants fromi the University of California Board of Research. We are greatly indebted to Professor A. W. Pollister, Dept. of Zoology, Columbia University, for allowing the senior author use of his laboratory facilities to conduct the measurements described herein. I Salvatore, C. A., Biol. Bull., 99, 112-119 (1950). 2 Caspersson, T., Skand. Arch. Physiol., 73, Suppl. 8 (1936). 3 Pollister, A. W., and Ris, H., Cold Spring Harbor Symp. Quant. Biol., 12, 147-157 (1947). 4Swift, H. H., Physiol. Zool., 23, 169-198 (1950). Swift, H. H., these PROCEEDINGS, 36,643-654 (1950). 6 Ris, H., and Mirsky, A. E., J. Gen. Physiol., 33, 125-146 (1949). 7 Leuchtenberger, C., Vendrely, R., and Vendrely, C., these PROCEEDINGS, 37, 33-37 *(1951). 8 Alfert, M., J. Cell. Comp. Physiol., 36,381-410 (1950). 9 Schrader, F., and Leuchtenberger, C., Exp. Cell Res., 1, 421-452 (1950). 10 Pollister, A. W., and Leuchtenberger, C., these PROCEEDINGS, 35, 66-71 (1949). 11 Leuchtenberger, C., Chromosoma, 3,449-473 (1950). 12 Mirsky, A. E., and Ris, H., Nature, 163, 666-667 (1949).