Quantitative study of the non‐circularity of myelinated peripheral nerve fibres in the cat

Abstract

One hind limb of each of 4 cats was chronically de-efferentated, or chronically de-afferentated. Up to 3 different muscle nerves were dissected from each limb and examined individually by EM. [The degree of noncircularity of all afferent axons or efferent axons in each muscle nerve was determined for group I, II and III afferent fibers, and .alpha. and .gamma. efferent fibers]. Non-circularity was expressed as the ratio (.vphi.) of axon cross-sectional area to the area of a circle with same perimeter. The axons appeared non-circular in vivo. Whether noncircularity allows axons to accommodate swelling during repetitive activity is discussed. Why .gamma. axons are more non-circular than .alpha. or group III axons in an anesthetized cat immediately prior to fixation, and why .alpha. axons may be more non-circular than axons in groups I and II is projected.