Galen dissected many animals; particularly goats, pigs, and monkeys, to demonstrate how different muscles are controlled at different levels of the spinal cord. He noted the functions of the kidney and bladder and identified seven pairs of cranial nerves. He also showed that the brain controls the voice. Galen revealed that arteries carry blood, disproving the 400-year-old belief that arteries carry air. Galen also described the valves of the heart and noted the structural differences between arteries and veins, but fell short of conceiving that the blood circulates. Instead, he held the erroneous belief that the liver is the central organ of the vascular system, and that blood moves from the liver to the periphery of the body to form flesh.
Galen was also highly praised in his time as a philosopher. In his treatise On the Uses of the Parts of the Body of Man he closely followed the view of the Greek philosopher Aristotle that nothing in nature is superfluous. Galen's principal contribution to philosophic thought was the concept that God's purposes can be understood by examining nature.
Galen's observations in anatomy remained his most enduring contribution. His medical writings were translated by 9th-century Arab thinkers and became highly esteemed by medical humanists of Renaissance Europe. Galen produced about 500 tracts on medicine, philosophy, and ethics, many of which have survived in translated form.
William Harvey (1578-1657)
William Harvey was an English doctor, who discovered the circulation of the blood and the role of the heart in propelling it, thus refuting the theories of Galen and laying the foundation for modern physiology.
Born on April 1, 1578, at Folkestone, Kent, Harvey received his B.A. from Gonville and Caius College, University of Cambridge, in 1597. He then went to Italy, where, at the University of Padua, he studied for five years under the celebrated anatomist Fabricius, who was already studying the valves of the veins. Having earned a medical degree (1602), Harvey returned to England and practised medicine in the London area. He was elected a fellow of the College of Physicians (1607) and appointed physician to St Bartholomew's Hospital. Recognized eventually as one of the most distinguished doctors in England, he became physician extraordinary to King James I, whom he attended in his last illness, and physician in ordinary to his son, Charles I.
From 1615 to 1656 Harvey served as Lumleian lecturer for the College of Physicians. As early as 1616 he discussed in his lectures the function of the heart and how it propelled the blood in a circular course. He arrived at his views not only by an elaborate series of dissections, but also by careful studies of the motion of the heart and blood in a wide range of living animals. These precise observations set a standard for future biological research.
Harvey formally presented his findings in 1628, when his Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (Anatomical Essay on the Motion of the Heart and Blood in Animals) was published. In this epoch-making work he explained the experimental method and gave an accurate account of the mechanism of the circulatory system. Because he had no microscope, the only major part of the process he omitted was the role played by the capillaries. He did, however, propose their existence, which was affirmed not long afterwards by the Italian anatomist Marcello Malpighi.
Harvey's De Motu Cordis subjected him to severe criticism by some contemporaries, but this was more than compensated for by the later widespread recognition of his contribution. He also undertook research in embryology, set forth in Exercitationes de Generatione Animalium (Essays on the Generation of Animals). The College of Physicians elected Harvey president in 1654, an honour he declined because of failing health. He died in London on June 3, 1657.
