A conspicuous portion of the peripheral nervous system is part of the 'vegetative nervous system'; it includes all the neurons which innerv- ate the viscera, salivary and lacrimal glands, the heart and blood vessels, all other smooth muscles of the body, notably the intrinsic muscles of the eye and the muscles of the hair. Only part of the system belongs to the peripheral nervous system: it has also its own nuclei and pathways in the central nervous system. The distinction between visceral and somatic functions is a very old one in our culture. With the development of neurology the notion of...