1. Bickel, H. and Hickmans, E. M. (1952). Archives of Disease in Childiood, 27, 348. and Thursby-Pelham, D. C. (1954). Ibid., 29, 224. Black,J.A.(1951). Ibid.,26,618.
2. Bray, P. T., Isaac, R. J. and Watkins, A. G. (1952). Ibid., 27, 341.
3. Clay, P. R. and Potter, C. T. (1955). bid., 30, 147.
4. Crumpler, H. R., Dent, C. E-, Harris, H. and Westall, R. G. (1951). Nature, Loud., 167, 307.
5. Datta, S. P., Dent. C. E. and Harris, H. (1950). Science, 112, 621.