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26 pages (2008/1915); 152KB downloadWOWIO Books
; ISBN: WOWIO-00383
In this essay William Harvey describes his observations and conclusions about blood circulation.
Before Harvey’s definitive discoveries, the prevailing notion of circulation was based on the Greek physician Galen. This view held that the blood in the left ventricle of the heart receded and flowed along the arteries, the blood in the right ventricle did likewise by way of the veins, and that some of the blood of the right side of the heart found an inexplicable channel to the left side through invisible pores of the wall of the heart, (the septum).
As the influence of science slowly grew, so too did understanding of the human body and how blood circulated. In 1534 Andreas Vesalius published the first modern anatomy book and, in a mainly theological book published in 1553, Michael Servetus became the first European to posit that some type of blood circulation involved the lungs.
By 1615 William Harvey had formulated his understanding of circulation of the blood based on his lectures on anatomy and his keen observation. Harvey wrote: “I frequently and seriously bethought me, and long revolved in my mind, what might be the quantity of blood which was transmitted, in how short a time its passage might be effected and the like; and not finding it possible that this could be supplied by the juices of the ingested aliment without the veins on the one hand being drained, and the arteries on the other hand becoming ruptured through the excessive charge of blood, unless the blood should somehow find its way from the arteries into the veins, and so return to the right side of the heart; I began to think whether there might not be a motion, as it were, in a circle. Now this I afterwards found to be true; and I finally saw that the blood, forced by the action of the left ventricle into the arteries, was distributed to the body at large, and its several parts, in the same manner as it is sent through the lungs, impelled by the right ventricle into the pulmonary artery, and that it then passed through the veins and along the vena cava, and so round to the left ventricle in the manner already indicated,— which motion we may be allowed to call circular.”
Harvey’s circulation theory was accepted and paved the way for modern physiology.