1. Deafferentation of not more than two limbs in the toad (Bufo bufo) only disturbs the normal diagonal pattern of ambulation in so far as a loss of muscular tone in the operated limbs introduces complications of a purely mechanical nature. In some cases the extent and smoothness of the protractor and retractor phases of the step may be modified.
2. Deafferentation of three or four limbs involves marked loss of muscular tone, and the excitability of the animal is greatly reduced. In some preparations the diagonal pattern of ambulation is preserved, in others it becomes irregular owing to a long latent period between the protraction of a forelimb and that of the contralateral hindlimb. Ambulation is ungainly, and fatigue rapidly sets in.
3. After total deafferentation of the whole body no ambulation has been observed. No ambulatory activity was observed in preparations in which all four limbs were deafferentated and in which the ventral, but not dorsal roots, of nerves V, VI, and VII were cut.
4. No positive evidence was found in favour of the view that the ambulatory rhythm originates in the central nervous system. Ambulation only occurs when the afferent and efferent nerve supply of at least one spinal segment is intact.