Praxagoras was an influential figure of medicine in ancient Greek. He was born on the Greek island of Kos in about 340 BC. Both his father, Nicarchus, and his grandfather were physicians. Very little is known of Praxagoras' personal life, and none of his writings have survived.
Galen (A.D. 129-216), a famous Greek physician, wrote of Praxagoras as this influential figure in Greek medicine and a member of the logical or dogmatic school. Galen also probably knew of the works of Praxagoras, writing on natural sciences, anatomy, causes and treatment of disease, and on acute diseases.
Praxagoras adopted a variation of the humoral theory, but instead of the four humors (blood, phlegm, yellow bile, and black bile) that most physicians held, he insisted on eleven. Like the other Greek physicians, he believed health and disease were controlled by the balance or imbalance of these humors. For example, if the proper amount of heat is present in the organism, the process of digestion is natural. Too little or too much heat will cause a rise in the other humors, which then produces certain disease conditions. He considered digestion to be a kind of putrefaction or decomposition, an idea that was held until the nineteenth century.
Praxagoras was also influential in the Alexandrian school in particular. After the death of Alexander the Great (356-323 B.C.), Egypt fell to the hands of General Ptolemy, who established a modern university with the first great medical school of antiquity. Human dissection was practiced, and although the university in Alexandria and its massive library was destroyed by bands of conquerors, later Arabic physicians made the efforts to preserve some of the writings. After the fall of the Byzantine Empire, Greek scholars brought back Greek medicine to the medical schools of the Western Renaissance.
Aristotle, Diocles, and Praxogoras insisted that the heart was the central organ of intelligence and the seat of thought. Praxagoras differed with the others in that he believed the purpose of respiration was to provide nourishment for the psychic pneuma, rather than to cool the inner heat.
Praxagoras was interested in pulse and was the first to direct attention to the importance of arterial pulse in diagnosis. He insisted that arteries pulsed by themselves and were independent of the heart. Herophilus refuted this doctrine in his treatise "On Pulses." In another area, Galen criticized Praxagoras for displaying too little care in anatomy. He suggested that Praxagoras did not arrive at his theories by dissection.
The beliefs of Praxagoras held sway for centuries. For example, for nearly 500 years after his death, many still believed that arteries did not contain blood but pneuma. His most famous pupil, Herophilus, was instrumental in establishing the marvelous medical establishment at Alexandria