1. Cavanagh, J. B., and Holland, P., Nature, 190, 735 (1961).
2. Hebb, C. O., Physiol. Rev., 37, 196 (1957).
3. Hebb, C. O., in Heffter Heubner Handbuch, “Anticholinesterases” chap. 3, edit. by Koelle, G. B. (in the press).
4. Shute, G. C. D., and Lewis, P. R., Bibl. anat., 2, 34 (Karger, Basel and New York, 1961).
5. Mitchell, J. F., J. Physiol., 155, 22–23P (1960); 17, 469 (1961).