1. Atkinson, M., Edwards, D. A. W., Honour, A. J., and Rowlands, E. N. (1957a). Lancet, 2, 918. - -(1957b). Ibid., 2, 1138.
2. Barrett, N. R. (1957). Surgery, 41, 881.
3. Botha, G. S. M. (1958). Brit. J. Surg., 46, 569.
4. Creamer, B., and Pierce, J. W. (1957). Lancet, 2, 1309.
5. Dornhorst, A. C., Harrison, Kent, and Pierce, J. W. (1954). Ibid., 1,695.