Harvey differed often and widely from Aristotle. Yet even in his old age he wrote: "The authority of Aristotle has always such weight with me that I never think of differing from him inconsiderately."[139] Cannot one fancy, may not one conjecture, that in the eyes of the discoverer of the circulation his great discovery, fundamental, new, and original, as he rightly claimed it to be, may at times have seemed to constitute a thorough correcting and filling in of a rough sketch dashed off at the Lyceum? Let us see.
Aristotle had no conception of anything resembling a circulation of the blood, nor any definite mechanical ideas as to its movement. While the vena cava as well as the aorta received blood from his valveless heart and yielded it to the body at large, blood ebbed back to the heart during sleep, and the warm nutrient liquid which the vena cava and the aorta yielded to the tissues had previously entered the heart continuously but in an imperfect state through both of these great vessels, to go forth again through both, perfected into blood and heated, with no perplexing differences of color noted between that in the great vein and that in the aorta. The relations between the food, the blood, the heart, and the body at large, though recognized to be complex, may well have presented themselves to Aristotle with something of the vagueness with which the relations between the food, the liquids, the contractile vacuole, and the living substance of a protozoön, present themselves to us. If the heart, retaining its Aristotelian powers, were found to receive the blood imperfect or impaired, but to receive it by the veins only, and to send it out, but only by the arteries, warmed and perfected or restored to perfection at its Aristotelian source; what have we but the systemic part of the circulation, as it may have pictured itself sometimes to Harvey?[140]
CHAPTER V
PHYSICIANS versus PHILOSOPHERS—HARVEY FOR THE PHILOSOPHERS
Thus it is striking to find Harvey, as the champion against Galen of a view essentially Aristotelian, entering the field of controversy where ancient Greek still met ancient Greek in the modern Europe of 1628.
The discoveries of the nerves and the valves of the heart had made great difficulties for the Aristotelian psychology and physiology shortly after Aristotle's time. We have seen that the semilunar valves were described, and their use noted, in a treatise included in the Hippocratic collection;[141] and all the valves, both arterial and auriculo-ventricular, were well recognized by Erasistratus, whose acquaintance we have made already, and who flourished about 300 B.C., Aristotle having died in 322 B.C. Erasistratus, we remember, was more than four centuries earlier than Galen and more than nineteen centuries earlier than Harvey.
That the heart throughout life is not only the source of the perfected blood, but gives out blood to the vena cava for distribution, had been rendered a hard saying, especially by the recognition of the tricuspid valve.[142] Galen, however, like the somewhat earlier Greek physician Aretæus, the Cappadocian,[143] was not confronted by this difficulty, for they both adhered to an ancient doctrine to be found in the Hippocratic treatise "On Nourishment," and there sketched with mingled clearness and vagueness in the following pithy saying:—
"Root of the veins, the liver; root of the arteries, the heart. Out of these wander into all parts blood and spirits, and through these heat comes in."[144]