The number and distribution of muscle spindles and tendon organs in the peroneal muscles of the cat.

An analysis has been made of the numbers and distributions of muscle spindles and tendon organs in the three peroneal muscles of the lower hindlimb of the adult cat. Both peronei brevis and tertius were richly supplied with spindle capsules and tendon organs in comparison with peroneus longus and other muscles of the cat's lower hindlimb. A large number of the capsules in each muscle was involved in tandem linkages, some of these capsules comprising only a bag and some chain fibres. Such capsules were especially prevalent in peroneus tertius. The numbers of extrafusal muscle fibres inserting into each tendon organ indicated that the activity of each motor unit should be monitored by at least one tendon organ. The distributions of the receptors are discussed in relation to the proportion and density of oxidative muscle fibres.