illustrious Aristotle, being the son of one of his daughters. It is said that he was so fond of anatomical pursuits that he retired from his practice in Alexandria, where he had settled, the better to gratify his taste. He wrote several treatises which are lost, and all we possess of his writings are a few fragments preserved in the works of Galen. From these we learn that he gave names to the auricles of the heart. He declared that the veins only were blood-vessels, and that the arteries, as their name implies, were air-vessels. The sole purpose of breathing was to fill the arteries with air; the air distended the arteries and made them beat, the air caused the pulse. The air, once in the left ventricle of the heart, became the vital spirits. The office of the veins was to convey blood to the extremities. When the veins carried blood only and the arteries were filled with vital spirits, then perfect health was maintained; but the entrance of blood into the arteries, which he admitted to sometimes occur, was abnormal and the source of disease—fevers when it entered some noble part or into a great artery, and inflammations when it was found in the less noble parts or in the extremities of the arteries. Thus it is seen that a stupendous error was established on a mighty authority. This error was destroyed by Galen four hundred years subsequently to the time of Erasistratus.
Claudius Galen (a. d. 131), next to Hippocrates the most celebrated physician the world ever produced, was born at Pergamus, in Asia Minor, about the year of our Lord 131, and educated in anatomy and medicine at Alexandria, then the most famous school in the world. At the age of thirty-four he settled at Rome, where he distinguished himself as a skillful practitioner, and became the physician to the Emperor Marcus Aurelius. The period of his death is not known, but it is stated that he was still living in the reign of Septimius Severus. Galen was a voluminous writer. A considerable number of his works are lost, and yet eighty-two treatises, more or less complete, survive and are in print. The writer of this sketch felicitates himself in the possession of a fine copy of the "Editio Princeps," in five ponderous folios, printed in Greek, by the celebrated Aldine press, at Venice, 1525. For a period of nearly fourteen centuries this vast mass—more voluminous than the entire Bible—was copied and recopied with the pens of scribes! Who can duly appreciate the value of the press? Galen proved that the arteries are blood-vessels, and thus destroyed the error of Erasistratus. He said, when an artery is opened, blood alone gushes out and no air. He tied an artery at two places a little distance apart, and on opening the vessel found it filled with blood only. The followers of Erasistratus wanted to know how the air from the lungs entered all parts of the body, to whom Galen replied that the air entered the lungs to cool the blood, after which it was expelled. This theory was held so late as the last century, even by the renowned physiologist Albrecht von Haller. Galen declared the pulse to be the
