The effect of cortisone on the repair of simple muscle injury was studied in rabbits. The histological findings in the crushed muscle are described for a period up to twenty-one days after injury.

Cortisone defers the onset of muscle regeneration, and retards its progress, but it does not change the course of the repair process or alter its eventual outcome under the conditions of the experiment.

This apparent refractoriness of repair of muscle, as compared with that of other connective tissues, is discussed.