METHOD In most of the experiments the 9th or 10th dorsal root ganglion of the frog (Hyla aurea, Rana cate8biana and R. pipiens) was used. These ganglia were dissected intact and in continuity with the roots and the trunk. The roots were severed adjacent to the spinal cord. The trunk was either cut prior to its entry intothe sciatic plexus, or followed into one or several of the branches of the plexus, eg (1) posterior femoral cutaneous nerve,(2) lateral crural cutaneous nerve,(3) tibial nerve, and (4) peroneal nerve (see Ecker, 1881). The fibres of the posterior femoral cutaneous nerve have been found to go mainly to the 10th dorsal root, while those of the lateral crural cutaneous nerve go mainly to the 9th. The preparations were always scrupulously cleaned to remove connective tissue and blood clots. Every effort was made to avoidinjuryof the preparation. In some experiments requiring a small number of nerve fibres the 11th dorsal root ganglion was used. This ganglion is very small, lying on the lateral surface of the columella. As a considerable segment of its nerve trunk is buried in the coccygeal muscle and as its roots are thin and penetrate