Direct evidence that nerve fiber degeneration may follow occlusion of groups of regional vasa nervorum, although provided by the experiments of Okada17(1905), Adams1(1943), Durward11(1948), and Roberts19(1948), has been scanty, and the conclusions to be drawn from the highly variable, but mainly negative, results of these experiments are uncertain. It has, however, been frequently assumed (Bacsich and Wyburn,21945; Sunderland,211946) that the longitudinal anastomotic vessels of epineural and intraneural plexuses obscure the importance of individual groups of vasa nervorum to such an extent that their role as sources of local blood supply may be virtually neglected. Such conclusions have almost exclusively been derived from experiments on small laboratory animals. Bentley and Schlapp4(1943), however, demonstrated that conduction may be substantially maintained in the partially devascularized sciatic nerve of the cat by diffusion from the vascular bed in which the