Of Cos, a physician of the second half of the 4th cent. bc. He is known only through the testimony of others, but it seems likely that he was a teacher of the great anatomist Herophilus of Chalcedon, and what little is known of him suggests that he was himself an anatomist of importance. Galen rather grudgingly acknowledges this, at the same time attacking his view that the nerves originate in the heart. He made important observations about the connection of the brain and spinal cord, and drew a distinction (perhaps being the first to do so) between veins and arteries, and their functions. He argued that the venous vascular system carried blood around the body, the arterial, pneuma. Details are lacking, but blood was apparently a product of healthy digestion, and pneuma was derived from inspired air, supplemented possibly by certain gaseous byproducts of digestion. Pneuma assumed a special status in Praxagoras' physiology, and was associated with the generation and communication of movement both in the arteries and the heart, and throughout the body. Praxagoras' complex physiological and pathological system ascribed the origins of most diseases to alterations in the state of humours, brought about by imperfect digestion. The four humours were themselves divided into as many as eleven sub-categories on grounds of taste, colour, and other properties. Little is known of his therapeutic practice, but it seems to have reflected closely his theoretical concerns with redressing highly complex humoral imbalances by means of dietary regulation and purging.
J. T. Vallance
Subjects: Classical Studies.