1. Alsberg, C. L., and Schwartze, E. W. (1919). J. Pharmacol., 13, 504.
2. Bonnell, J. A. (1955). Brit. J. industr. Med., 12, 181.
3. Kazantzis, G., and King, E. (1959). Ibid., 16, 135.
4. Dalhamn, T., and Friberg, L. (1957). Acta path. microbiol. scand., 40, 475.
5. Fourman, P., McCance, R. A., and Parker, R. A. (1956). Brit. J.