Page:Popular Science Monthly Volume 2.djvu/699

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N all ages the most different opinions as to the seat and the principle of life have been expressed; yet, the systems bequeathed to us by the ancients on this subject contain a general belief, simple enough to be very widely shared, and seemingly well founded enough to endure for centuries. One fact of commonest observation death resulting from haemorrhage gave rise to the notion that life dwells solely in the blood. Homer's heroes breathed out their souls with their blood; among the Hebrews, as among the Greeks, offering the sacrifice of a life, and shedding the blood of a victim, were equivalent expressions. On this point the religions of the West have consecrated the belief of all ages and all people; a verse in Leviticus thus sums it up: "The life of all flesh is in the blood."

From Galen to Harvey, men of science supposed that the heart only sends out the fluid of the blood from the centre to the surface. In their theories, the blood was incessantly formed and renewed within the liver, and was impelled by centrifugal force into the veins and arteries alike. Harvey first demonstrated that the blood returned in its course. "It moves," he said, "in the same circle, as the planets all describe the same orbit in moving through space." The idea of the transfusion of blood takes its starting-point from the discovery of Harvey. As soon as it was known that the blood can return to the heart, and be taken up again by the vessels, what was more natural than to seek to introduce it into a diseased body? Is not the blood still regarded as the sole principle of life, as it was in the early ages of medicine? And, since it can be transfused in kind, we shall be able to restore health, to heal disorders, perhaps, even to lengthen life. In a moment of pride the human mind believes it has penetrated the secret of life, and supposes that henceforward it will be its master. The most famous alchemists of the middle ages never surrendered themselves to hopes so wild. Besides, the sixteenth and seventeenth centuries saw the birth of so many discoveries in natural sciences, that nothing seemed impossible. The schools of medicine enter with feverish ardor on these questions, so full of promise; but, amid the light that bursts upon them, they often neglect that severe observation of facts which led to the discovery of the circulation. Physicians of that day trouble themselves very little with inquiries whether the ancient notions about the blood are true or false; they accept them without reserve, and publish them abroad with those forms of discussion and those obsolete principles which brought upon them the well-deserved