An electron microscopic study on differences in the fine structures of motor endplate in red, white and intermediate muscle fibers of rat intercostal muscle. A preliminary study

An electron microscopic study on the fine structural differences of motor endplates among the red, white and intermediate muscle fibers of the rat intercostal muscles was made and the following results were obtained. 1. In the motor endplate of the red fiber, the junctional folds were poorly developed and their number was small. 2. In the motor endplate of the white fiber, the junctional folds were well developed and their number was far more numerous than those in the red fiber. 3. The fine structure of the motor endplate of the intermediate fiber was of an intermediate character between the red and white fiber.