For the past 30 odd years, electromyography has been used to aid in the understanding and investigation of abnormal function or of dysfunction of the lower motor neuron, more specifically of the motor unit. During the latter part of this period, clinical electromyography has been developed specifically to understand the abnormality of dysfunction of the lower motor neuron (neuropathies) as well as of the muscle itself (myopathies). As a result of these clinical studies, some questions have arisen regarding the true nature of denervation activity. For example, is this activity an inherent property of the skeletal muscle fiber as an organ itself, having existed from intrauterine life? Is denervation activity a reversion of the inherent function of the muscle fibers to their infantile preinnervated state? It is assumed that the motor nerve has two basic controls over the muscle fibers: (a) trophic control, and (b) physiological control of its excitable