Neuron doctrine and electrophysiology.

The neuron doctrine, which we chiefly owe to Cajal (1), was unquestionably a giant stride forward in the understanding of the substratum of nervous function. It forms the basis of all modem work on the nervous system. It asserts that the nerve cell and its processes, together called the neuron, form the cellular units of the nervous system which are directly involved in nervous function; that all nerve fibers are neuronal processes; that the neuron and all its extensions develop embryologically from a single neuroblast; and that the neuron is a trophic unit, all its processes being dependent upon the nucleated cell body for their maintenance and regeneration. Although this is not inherent in the original anatomical concept, the neuron has classically come to be regarded as a functional unit, and it is here that newer information forces a reappraisal.