1. Cf. Caspersson, T., Skand. Arch. Physiol., 73, Suppl. 8 (1936).
2. Buchholz, J. T., Science, 105, 607 (1947).
3. Cf. Serra, J. A., Portug. Acta Biol., 2, 25 (1947).
4. Schryver, J., M.S. thesis, Polytechnic Inst., Brooklyn (1948).
5. Hillier, J., and Ramberg, E. G., J. App. Phys., 18, 48 (1947).