1. Barker, P. S., Wilson, F. N., and Johnston, F. D. (1943). Amer. Heart J., 26, 435.
2. Barker, P. S., Wilson, F. N., and Johnston, F. D. and Wishart, S. W. (1943). Ibid., 25, 765.
3. Brown, W. H. (1936). Ibid., 12, 307.
4. Campbell, M., and Elliott, G. A. (1939). Brit. Heart J., 1, J23.
5. Textbook of Medicine;Conybeare, J.J.,1942