Within the last half of the twentieth century, two fundamental properties of nerve were established: in midcentury, the ionic nature of the propagated action potential; and, later in the century, the process in the fibers known as axonal flow, axoplasmic transport, axonal transport, neuroplasmic transport, and so on. By means of the transport mechanism, essential components synthesized in the nerve cell bodies are carried out within the relatively long length of nerve fibers to maintain their viability and function. Components transported include the ion channels and ion pumps needed to maintain membrane potentials all along the length of the fibers, metabolic and structural components supporting the form and viability of the fibers, and substances providing for reception at sensory terminals and neurotransmitters at motor terminals. This is indeed a protean mechanism, fundamental for an understanding of modern neuroscience and a rational basis for interpretation of neuropathies and eventually their therapy.

Although the discovery of the properties and molecular nature of the transport mechanism and related topics is a major theme, this account is not restricted to the last half century. The concept can be traced back to its earliest beginnings in the sixth and fifth centuries b.c., respectively, when philosophy and science had their origins in ancient Greece. Nerves were then conceived of as channels carrying sensory impressions by animal spirits to the brain where consciousness awareness and reasoned judgment were located, and from it willed commands were carried by nerves to actuate the muscles.