Distribution of Muscle Fibers of Three Types Differentiated by Succinic Dehydrogenase Activity in the Skeletal Muscle

A histochemical study was made on the succinic dehydrogenase activity of the M. gastrocnemius, M. soleus, M. quadriceps femoris, M. biceps femoris, M. masseter, M. temporalis and M. digastricus in the rat, rabbit and cat. According to the intensity of the succinic dehydrogenase activity, the muscle fibers were divided into three types, i. e. white fibers with a low, red fibers with a high, and medium fibers with an intermediate enzymatic activity.Every muscle studied was composed of two or three types of muscle fiber, and never of a single type of fiber. The ratio in number of muscle fibers of three types varied in different muscles. The limb muscles contained white and medium fibers in higher percentage, while the jaw muscles composed mainly of red and medium muscle fibers in these three animals.White fibers were generally more numerous in the superficial part of the muscle, whereas red and medium fibers in the axial or deep portion of the muscle.