CYTOCHROME C REDUCTASE AND MENINGOPNEUMONITIS ORGANISMSstages of the disease. Before other histological alterations appear, white fibers enlarge and manifest the oxidative enzyme characteristics of red muscle fibers. Apparently, muscle fibers early in the myopathic process contain more enzymes, both oxidative and glycolytic, than do the normal muscle fiber. With the development within a muscle fiber of coagulation necrosis, reactions for both oxidative and glycolytic enzymes are diminished or completely absent. The early and extensive vulnerability of the pectoral muscle of chickens for dystrophic change is an index of its high white fiber content. With reference to enzyme activity in the muscle fibers undergoing myopathic changes, apparently two processes occur during the process: at first some enzymes are increased in amount ; then when necrosis occurs, various enzymes examined in this study are lost from the damaged fibers.It is not yet possible to state that a specific enzyme disorder is responsible for the dystrophic process. The similarity of lesions in the genetic and nutritional dystrophic disorder in the chickens suggests that a similar type of disturbance in metabolism is present in both conditions.