Five Quarts_ A Personal and Natural History of Blood - Bill Hayes [20]
“The movement of the blood in a circle is caused by the beat of the heart,” he declared, summing up in one sentence his entire theory of the circulatory system. Then, as if to head off any But what about . . . ? from the unconvinced, Harvey added, “This is the only reason for the motion and beat of the heart.”
Through animal vivisection, human dissections, and observations of living patients, Harvey poked more holes in Galenism. Blood did not ebb and flow within the same vessels, as the Greek physician had taught. Instead, the arteries carry it away from the heart, and the veins bring it back. Valves inside the veins help the depleted blood make the return trip. Further, although he couldn’t explain how, Harvey theorized that blood passes via some unknown mechanism from the arteries into the veins. The crude new microscopes of his day were not nearly powerful enough to reveal the minute bridging vessels now known as capillaries. In a final slap to Galen, Harvey also proved that the arteries themselves did not contract and dilate like blacksmith bellows, thereby producing the pulse. “The pulsation of the arteries,” Harvey wrote, “is nothing else than the impulse of the blood within.”
William Harvey
Accomplishments notwithstanding, Harvey was not necessarily a “better” scientist than Galen, contemporary writer-physician Jonathan Miller contends. “The difference between the two men is not one of ingenuity and skill—in fact, if these were the sufficient conditions of scientific progress, Galen rather than Harvey might have been the discoverer of the circulation of the blood.” Instead, the difference between them was one of “metaphorical equipment,” Miller argues in his book The Body in Question (1978). Galen likened the heart to a common household item of his time, the oil lamp: The organ heated and transformed blood from a dusky fuel to a flaming scarlet stream, illuminated by Vital Spirits. In his reckoning, however, that was the extent of the heart’s role. “Galen’s inability to see the heart as a pump was due to the fact that such machines did not become a significant part of the cultural scene until long after his death,” Miller states. By the end of the sixteenth century, though, mechanical pumps began to be widely employed in mining, firefighting, and civil engineering, such as in the design of ornamental public fountains. Therefore, when Harvey conducted his experiments (among them, watching as hearts slowly failed during animal vivisections), he was able to see the organ for what it was: a pump, resembling the marvelous inventions in use around him.
With the medical community electrified by Harvey’s discovery, a new interest was sparked in injecting substances directly into the bloodstream. But a simple means for such a procedure did not exist. Enter: British architect Christopher Wren. In 1656 Wren fashioned a crude syringe from a hollow feather quill fastened to a bladder and was able to pump opium straight into a dog’s vein, thus creating a method for IV therapy as well as one very mellow pooch. Wren’s success inspired others to infuse animals with not just medications but also wine, beer, milk, urine, anything liquid—often with fatal results—and eventually to try blood. In 1665 the British anatomist Richard Lower performed the first successful blood transfusion in animals, linking