The Innervation of Muscle Spindles in an Intrinsic Muscle of the Hind Foot: The Superficial Lumbrical of the Cat

An important, if largely unrecognised, feature of the design of the mammalian skeletomotor proprioceptive system is the characteristic variation from muscle to muscle in the provision of its components. This applies not only to the relative abundance of muscle spindles, but also to quantitative differences in their sensory ending complement (Banks & Stacey, 1988). Furthermore, Banks (1994) has shown that there is a linear correlation between the numbers of static γ and afferent axons supplied to each spindle, at least in the tenuissimus. Considerably more comparative information of this type is needed for a fuller understanding of the contribution that proprioception makes to particular motor tasks. Here we describe some preliminary observations on the innervation of the superficial lumbrical muscle of the cat’s hind foot.