Myotonic electromyographic activity in complexus muscles of normal and dystrophic chicks.

Myotonic-like, "dive-bomber" discharges were recorded from complexus ("hatching") muscles of both normal and dystrophic chicks at 5 days ex ovo and were recordable from dystrophic, but not from normal, pectoralis major muscles at 28 days ex ovo. The complexus muscle, therefore, provides the opportunity to study in young, normal animals, a form of electrophysiological activity previously considered a sign of neuromuscular abnormality.