1. Swingle, K. F., Amer. J. Vet. Res., 14, 493 (1953). Whiting, F., Connell, R., and Forman, S. A., Can. J. Comp. Med. Vet. Sci. (in the press).
2. Hurd, Charles B., and Sheffer, Howard, E., J. Phys. Chem., 45, 588 (1941). Iler, R. K., J. Phys. Chem., 57, 604 (1953).
3. Holt, P. F., and Yates, D. M., Brit. J. Exp. Pathol., 35, 52 (1954).
4. Treadwell, W. D., and König, W., Helv. Chim. Acta, 16, 478 (1933).
5. Iler, Ralph K., “The Colloid Chemistry of Silica and Silicates”, 47 (Cornell Univ. Press, Ithaca, New York, 1955).