The history of the discovery of the vegatative (autonomic) nervous system.

PREHISTORYt THE sTRucuREs which are known today as the peripheral vegetative nervous system were morphologically rather well known to Galen (A.D. 130-200), the greatest anatomist and physiologist of antiquity." His descriptions suggest that he gained his knowledge mostly from dissecting pigs. His so-called 'sixth cranial nerve' comprises what we call today the ninth (glossopharyngeal), tenth (vagus), eleventh (accessory) nerves and the sympathetic chain. He described the superior cervical ganglion, the inferior cervical ganglion, the semilunar ganglion and the rami communicantes. These anatomical notions are still to be found in the basic Traite des nerfs of Tissot in 1778.' Unfortunately Galen's physiological ideas are marred by his teleological zeal. He feels that these nerves are 'soft', because they come from the brain. Being soft they have to be purely sensory. He 'proves' then that they are there for this purpose anyhow. If by accident one of the nerves shows motor functions, it has in Galen's opinion dried up, and has become hard, and therefore motor. These nerves are hollow and make the so-called animal spirits go from one organ to the other, producing thus the phenomenon of 'sympathy'. Sympathy is an old and vague notion. In this case it accounts for the co-operation or co-ordination of organs, like irritation of the stomach producing syncope or convulsions by being transmitted via brain and nerves to the heart. Galen knew also a humoral kind of sympathy via bloodvessels, like for instance the relations of the pregnant uterus with the mammary glands.' As is well known, medical science remained stationary at best from Galen to the Renaissance. Even Vesalius, who in many points improved Galen's anatomical notions, left them unchanged as far as the so-called 'sixth nerve' was concerned. It is only his younger contemporary, the great Eustachius (1524-74), who in 1563 regarded the vagus and sympathetic as two different nerves. He described the sympathetic as the continuation of the abducens, our sixth cranial nerve.8 An important event in the