Three Scientific Revolutions: How They Transformed Our Conceptions of Reality Read Online Free PDF Page A

moon’s diameter and distance from the earth. However, as important as these previous contributions were, it was Ptolemy’s Almagest (the title of his major work later given by the Arabs) written in Alexandria in the second century CE whose astronomical system with its epicycles, eccentrics, and equants, to accommodate the astronomical observations that did not fit the spherical orbits and uniform motion of Eudoxus’ celestial system, that eclipsed Aristarchus’ heliocentrism and that prevailed until its rejection by Copernicus.
    But, it was Eratosthenes, the famous librarian of Alexandria in the third century BCE, having acquired a notable reputation as an astronomer, mathematician, geographer, and philologist, who rivaled Aristotle as “the most learned man of antiquity.” Known for his invention of the “Sieve of Eratosthenes” for deriving prime numbers and his astute geometrical studies, his mathematical gifts facilitated his remarkable geographical discoveries. He drew the most accurate map of the world for the time showing the circumference of the earth divided into latitudes and longitudes, proposed that the oceans were so united that it would be possible to reach India by sailing west and, most importantly, introduced an ingenious mathematical method for measuring the circumference of the earth within an accuracy of 200 miles.
    Another amazing researcher in Alexandria of the third century BCE was Herophilus of Chalcedon, one of the first to practice human dissection and consequently is considered the outstanding anatomist of ancient Greece. Among his discoveries was that the arteries carried blood from the heart to all parts of the body, the usefulness of the pulse in diagnosing various illnesses, and that by dissecting the brain various bodily functions could be correlated with specific brain regions, a remarkable discovery for the time. He was succeeded by Erasistratus, who is said to have practiced vivisection in Alexandria also in the third century. He, too, is famous for having discovered the functions of various body parts, such as the valves in the heart and distinguishing between the arteries and the veins detecting their interconnection. (For more on ancient medicine see volume one of my book From Myth to Modern Mind: A Study of the Origins and Growth of Scientific Thought .)
    Still, despite the belief that revealed scripture was far superior to scientific knowledge, the best known of the physiologists is Galen of Pergamum, who in his youth studied in Alexandria and other centers of learning acquiring the vast knowledge of medicine for which he is famous and then settling in Rome for the rest of his life in the second century CE. Three reasons account for his prominence: (1) his encyclopedic knowledge; (2) that while most of the works of the previous Ionian scholars were lost in the various fires that destroyed the Royal Library in Alexandria his, fortunately, were preserved; and (3) that his own physiological research was so advanced that it prevailed until replaced by the work of Andreas Vesalius in the sixteenth century.
    His major achievement was his description of the physiological organs and functions integrating the circulatory, respiratory, and nutritive systems. He described how the “cosmic pneuma” was inhaled through the trachea, carried to the lungs, and then transmitted by the Vena arterials to the left cavity of the heart where it was mixed with the blood. The blood itself was derived from nutriment taken by the portal vessel from the intestines to the liver where it was converted to venous blood by combining with a second spirit or pneuma, called “natural spirit,” which is viewed as essential for life.
    The combination of natural spirit and nutriment composing the venous blood in the liver is then dispersed by the veins throughout the venous system. When some of this venous blood is carried to the right cavity of the heart it divides into two