1. Barkley, H., and Cardozo, R. H. (1957). Thorax, 12, 264.
2. Bass, H. E., and Singer, E. (1951). Ann. intern. Med., 34, 498.
3. Campbell, J. A. (1957). In Bronchopulmonary Diseases, ed. E. A. Naclerio, p. 631.
4. Hoeber, New York. Ch'in, K. Y., and Tang, M. Y. (1949). Arch. Path., 48, 221.
5. Hochberg, L. A., and Schacter, B. (1957). In Bronchopulmonary