The aim of this study is to determine the mechanism in neurons whereby materials are carried from their site of synthesis in the nerve cell bodies outward inside the nerve fibers. The composition of these materials and their relation to nerve function is to be determined. Some substances are considered to act as metabolites or as enzymes, as trophic agents controlling the form and function of the fiber, others to maintain synaptic transmission and to control the function of muscles and other cells at the nerve terminals. An understanding of axoplasmic transport is most likely to help understand diseases where a failure of synthesis of required substances or their normal transport are suspected to underlie altered form and function.