1. See Levi-Montalcini, R., Science, 143, 105 (1964).
2. Berk, L., Filipe, I., and Zaimis, E., J. Physiol., 177, 1P (1965).
3. Zaimis, E., J. Physiol., 177, 35P (1965).
4. Greene, E. C., Anatomy of the Rat (Hafner, New York, 1955).
5. Bertler, A., Carlsson, A., and Rosengren, E., Acta Physiol. Scand., 44, 273 (1958).