1. Evidence is given of successful direct implantation of a motor branch of the ulnar nerve to the denervated flexor carpi radialis muscle in the dog with the formation of new motor end-plates.

2. A method is described of measuring four muscle parameters-volume, myoneural delay, rate of contraction and greatest developed tension-which allows a quantitative comparison of the muscle in its original state with that after it has been changed experimentally.

3. By use of this method it was found that the direct implantation of a new motor nerve restored the denervated muscle volume in twenty weeks and that at least 50 per cent of its original strength was recovered.

4. The success of motor nerve transplantation is likely to be influenced by the length of time lapsing between denervation and implantation, by the number of functioning motor fibres in the transplanted nerve, and by the amount of recovery achieved in the afferent and spindle efferent systems.