Muscle Dystrophy in Mice of the Bar Harbor Strain

The presence of fibrillation in the muscles of the Bar Harbor strain of dystrophic mice has previously been reported from this laboratory.¹We have observed that the electromyogram from dystrophic mice of this strain is strikingly similar to that recorded from muscles of patients suffering from dystrophia myotonica. The muscles of such patients and animals are hyperirritable, and the records obtained by the insertion of a concentric needle electrode reveal the presence of short motor volleys of high frequency against a background of electrical activity characteristic of denervated muscle. In order to demonstrate the presence of fibrillation, free of the superimposed activity from innervated structures, it was decided to study the electrical activity of muscles in dystrophic mice and patients in whom the motor nerves were blocked. The identification of characteristics common to both the dystrophy in this strain of mice and a particular form of dystrophy in man