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right ventricle sending its charge into the lungs, by the vessel which is called vena arteriosa, but which, in structure and function and in all things else, is an artery; the left ventricle sending its charge into the aorta, and through this, by the arteries, into the body at large.'

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This, then, is the course of the blood within the heart, from the two cisterns of venous blood-the auricles; it flows into the two ventricles—the right ventricle sends its charge into the lungs, the left into the aorta. What becomes of the blood sent by the right ventricle into the lungs? "The blood percolates the substance of the lungs from the right ventricle of the heart into the pulmonary veins and left ventricle." This is the lesser circulation. What becomes of the blood discharged by the left ventricle into the aorta? The answer to this question is given in the eighth chapter, which, as one of the most interesting historical documents in medical literature, we shall give entire :

"Thus far I have spoken of the passage of the blood from the veins into the arteries "—that is, the percolation through the lungs-" and of the manner in which it is transmitted and distributed by the action of the heart,-points to which some, moved either by the authority of Galen or Columbus, or the reasonings of others, will give in their adhesion. But what remains to be said upon the quantity and source of the blood which thus passes, is of so novel and unheardof a character, that I not only fear injury to myself from the envy of a few, but I tremble lest I make mankind at large my enemies. So much doth wont and custom, that become as another nature, and doctrine once sown that hath struck deep root, and respect for antiquity, influence all men. Still the die is cast, and my trust is in the love of truth, and the candour that inheres in cultivated minds. And, sooth to say, when I surveyed my mass of evidence,

1 Harvey's Works, p. 31.

whether derived from vivesections and my various reflections on them, or from the ventricles of the heart and the vessels that enter into and issue from them, the symmetry and size of these conduits-for Nature doing nothing in vain, would never have given them so large a relative size without a purpose, or from the arrangement and intimate structure of the valves in particular, and of the other parts of the heart in general, with many things besides, 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 becoming drained, and the arteries on the other getting 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 indicated. Which motion we may be allowed to call circular, in the same way as Aristotle says that the air and the rain emulate the circular motion of the superior bodies; for the moist earth warmed by the sun evaporates; the vapours drawn upwards are condensed, and descending in the form of rain moisten the earth again, and by this arrangement are gene rations of living things produced; and in like manner, too, are tempests and meteors engendered by the cir

cular motion, and by the approach and recession of the


"And so in all likelihood does it come to pass in the body, through the motion of the blood; the various parts are nourished, cherished, quickened by the warmer, more perfect, vaporous, spirituous, and, as I may say, alimentive blood; which, on the contrary, in contact with these parts, becomes cool, coagulated, and, so to speak, effete; whence it returns to its sovereign, the heart, or to the inmost home of the body, there to recover its state of excellence or perfection. Here it resumes its due fluidity, and receives an infusion of natural heat-powerful, fervid, a kind of treasury of life, and is impregnated with spirits, and, it might be said, with balsam; thence it is again dispersed, and all this depends on the motion and action of the heart.

"The heart consequently is the beginning of life; the sun of the microcosm, even as the Sun, in his turn, might well be designated the heart of the world; for it is the heart, by whose virtue and pulse the blood is moved, perfected, made apt to nourish, and is preserved from corruption and coagulation; it is the household divinity which, discharging its function, nourishes, cherishes, quickens the whole body, and is, indeed, the foundation of life, the source of all action. But of these things we shall speak more opportunely when we come to speculate upon the final course of this motion of the heart.

"Hence, since the veins are the conduits and vessels that transport the blood, they are of two kinds-the cava and the aorta; and this is not by reason of there being two sides of the body, as Aristotle has it, but because of the difference of office; nor yet, as is commonly said, in consequence of any diversity of structure; for in many animals, as I have said, the vein does not differ from the artery in the thickness of its tissues, but solely in virtue of their

several destinies and uses. A vein and an artery, both styled vein by the ancients, and that not undeservedly, as Galen has remarked, because the one, the artery to wit, is the vessel which carries the blood from the heart to the body at large; the other, or vein of the present day, bringing it back from the general system to the heart; the former is the conduit from, the latter the channel to, the heart; the latter contains the cruder, effete blood rendered unfit for nutrition; the former transmits the digested, perfect, peculiarly nutritive fluid.”1

On reading this document now, one is apt to accuse Harvey of timidity in imagining that by its publication he could possibly make "mankind his enemy." Alas! his prognostication of evil was more than fulfilled;-by the world at large he was scouted as a crack brained fool; and by his own colleagues, in whose love of truth and candour, as having cultivated minds, he reposed his trust, he was avoided as a heretic. In derision he was called "Circulator," or quack, and there was a current medical proverb—“ Malo cum Galeno errare quam cum Harveio esse circulator."

Thus, in the year 1628, two years after the death of Lord Bacon, was the solution of the greatest problem in vital mechanics given to the world. Harvey, after this, devoted himself to the study of Generation, and greatly advanced the knowledge of that mysterious subject. He also studied, and probably wrote upon one of the most puzzling problems of vital chemistry-Respiration; and he seems to have had a true, although necessarily vague idea, of this process; for he says "If any one will carefully attend to these circumstances, and consider a little more closely the nature of air, he will, I think, allow that air is given, neither for the 'cooling,' nor the nutrition of animals; for it is an established fact, that if the foetus has once respired, it may be more quickly suffocated, than if it had been entirely excluded 1 Harvey's Works, p. 47.

from the air it is as if heat were rather enkindled within the fœtus, than repressed by the influence of the air. This much, by the way, on the subject of Respiration; hereafter perhaps, I may treat it at greater length." That Harvey should have suspected the truth, to be revealed long afterwards, that heat was enkindled by respiration, is a most remarkable proof of his genius. For Chemistry may be said not to have been born till after the words just quoted were written. Harvey published his work on Generation in the year 1651, and at that time Robert Boyle was twenty-five years of age. Boyle has been called the Father of Modern Chemistry, and we are now on the threshold of the chemical era of medicine.

1 Harvey's Works, p. 530.

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