Recovery in partly paralysed muscles.

Until recent years it was widely held that damage to part of the nerve supply of a voluntary muscle had a permanent effect and that the surviving nerve fibres were unable to reinnervate muscle fibres deprived of their nerve supply. It was assumed that the only possibility of recovery of power in the muscle was by hypertrophy of muscle fibres whose nerve supply had escaped damage. The problen has recently been approached by both physiological and histological methods. Van Harreveld (1945) showed that the contraction force of incompletely denervated muscles begins to improve about two weeks after operation and increases for six months. Edds (1950) and Hoffman (1950), in histological studies of rat muscle incompletely denervated by division of anterior primary rami, found evidence of new fibres retracing the empty neurilemmal tubes to the denervated motor end-plates. That a similar process occurs in skin partly deprived of its sensory nerve supply has been shown by Weddell, Guttmann and Gutmann (1941). It has not yet been generally accepted that surviving axons in incompletely denervated muscle can extend their existing field of innervation by producing new fibres. The problem is of great practical importance, for if this process takes place after an attack of poliomyelitis, and if ways could be found to promote it, a real advance in treatment would be at hand. The aim of this study has been to obtain further histological evidence of the extent and duration of this process : limb muscles of the rabbit have been examined for evidence of the development of new fibres for periods of up to three months after incomplete denervation.