Praxagoras () was a figure of medicine in ancient Greece. 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. History Between the death of Hippocrates in 375 BC and the founding of the school in Alexandria, Egypt, Greek medicine became entrenched with speculation, seeing little advances in medicine. During this period four men took up the study of anatomy: Diocles of Carystus (fl. 4th century BC), Herophilus (c. 335–280 BC), Erasistratus (c. 304–250 BC), and finally Praxagoras. Galen (AD 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 19th century. Praxagoras was also influential in the Alexandrian school in particular. After the death of Alexander the Great (356–323 BC), 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, mostly by Herophilus and Erasistratus; Praxagoras was Herophilus' teacher. 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. Praxagoras' theory of circulation Praxagoras studied Aristotle's (384–322 BC) anatomy and improved it by distinguishing between artery and veins. He saw arteries as air tubes, similar to the trachea and bronchi, which carried pneuma, the mystic force