Dr. Baas, in his account of the Anatomy, Physiology, and Medicine of Erasistratus, says that he divided the nerves into those of sensation and those of motion. The brain substance is the origin of the motor and the brain membranes that of the sensory nerves.[415] Like Herophilus, he confounded the nerves and ligaments. He described accurately the structure, convolutions, and ventricles of the brain. He thought that the convolutions, especially those of the cerebellum, are the seat of thought, and located mental diseases in the brain. He knew the lymph and chyle vessels, and the chordæ tendineæ of the heart. He assumed the anastomoses of the arteries and veins. The pneuma in the heart is vital spirits, in the brain is animal spirits. Digestion is due to the friction of the walls of the stomach. He thought that the bile is useless, as is the spleen and other viscera. He shows some acquaintance with pathological anatomy, as he describes induration of the liver in dropsy. His idea of the cause of disease is plethora and aberration of the humours. Inflammation is due to the detention of the blood in the small vessels by the pneuma driven from the heart into the arteries; fever occurs when the pneuma is crowded back to the heart by the venous blood, and blood gets into the large arteries. Dropsy always proceeds from the liver. He discarded bleeding and purgation; recommended baths, enemeta, emetics, friction, and cupping. He was, thinks Dr. Baas, a forerunner of Hahnemann in the doctrine of small doses, as he prescribed three drops of wine in bilious diarrhœa. He opened the abdomen to apply remedies directly to the affected part, and invented a kind of catheter.[416] Erasistratus was the first to describe a species of hunger, to which he gave the name Boulimia—a desire for food which cannot be satisfied. In his account of the complaint he mentions the Scythians, who, when obliged to fast, tie bandages round their abdomens tightly, and this stays their hunger.[417]