1. Gibson, T., and Medawar, P. B., J. Anat., Lond., 77, 299 (1943).
2. Medawar, P. B., J. Anat., Lond., 78, 176 (1944).
3. Medawar, P. B., J. Anat., Lond., 79, 157 (1945).
4. Summarized by Medawar, P. B., Bull. War. Med., 4, 1 (1943).
5. Gorer, P. A., J. Path. Bact., 47, 231 (1938).