Histochemical Demonstration of the Three Types of Intrafusal Fibers of Muscle Spindles, a Study on Oxidative Enzymes

Histochemical studies of several oxidative enzymes of the muscle spindles in mouse limbs were carried out. Observations elucidated the existence of the three types of intrafusal fibers which can be distinguished from each other by the difference in the activity of oxidative enzymes as in the muscle fibers, i. e., the first one is the "red intrafusal fibers" and has the most intense activity of oxidative enzyme, the second one the "white intrafusal fibers" with a minimal activity, and the third, "medium intrafusal fibers" being distinguished by their oderate activity of oxidative enzymes from the others.