1. Florey, H., Carleton, H. M., and Wells, A. Q. (1932). Brit. J. exp. Path., 13, 269.
2. Higgins, I. T. T., Oldham, P. D., Cochrane, A. L., and Gilson, J. C. (1956). Brit. med. J., 2, 904.
3. Hilding, A. C. (1943). Ann. Otol. (St. Louis), 52, 5.
4. Hilding, A. C. and Hildinq, D. (1948). Ibid., 57, 324.
5. Houston, J. C., De Navasquez, S., and Trounce, J. R. (1953). Thorax, 8, 207.