point of the heart be cut off, blood is seen to spurt from the ventricles upon each contraction of the auricles. From this we learn that the ventricles do not fill in virtue of any attractive power of their own, but from having blood thrown into them by the action of the auricles.

In the heart of an animal when moribund, the ventricles are observed to cease beating sooner than the auricles, the left always giving in before the right, which, indeed, may be seen to flutter feebly when all else is still. Life, therefore, appears to linger longer in the right auricle than in any other element of the heart,—even as in the incubated egg, a reddish palpitating point, which is gradually developed into the auricle, is the part of the future chick which first by its motion gives signs of life, as in the adult creature it is the last to die.

By the reciprocating dilatations and contractions of the auricles and ventricles, there is, consequently, an alternate reception and delivery of blood-reception by the auricles from the veins, delivery from them to the ventricles; reception in turn by the ventricles from the auricles and delivery by them to the arteries, with the accompanying sensible pulse of the heart and efferent vessels. The fact of the pulmonary artery and pulmonary vein proceeding from the heart and losing themselves in the lungs, which was so great a puzzle to the old physiologists, with their natural blood for nutrition and their spirituous blood for heat and

vital endowment, was no enigma to Harvey with the one blood alternately dark and florid-dark whilst venous before passing through the lungs, florid after this whilst in course of transmission by the aorta and its subdivisions to minister to the requirements of the body.

With his predecessors Harvey speaks at one time of the blood being transmitted through the lungs for the purpose of attaining its final perfection; at another of having its heat damped down or mitigated; and at yet another, of its possibly acquiring rather than losing heat through exposure to the inbreathed air. He, consequently, delivers himself doubtfully on this important subject; he has not made up his mind upon it, and so refers to a treatise he intended to publish on the question, which, unhappily, never appeared.

Harvey is next at considerable pains to show that from the structure of the several parts of the heart— the arrangement of the valves at its orifices, &c., the blood must necessarily pass in a ceaseless stream from the right to the left side of the organ by way of the lungs. Until the "Exercise on the Motion of the Heart and Blood" appeared and settled the question for ever, this, although acknowledged by one or two of his predecessors, was really a moot point with the majority of them, the very latest and most accomplished of them all, Andrea Cesalpino, as we have seen, still maintaining that the blood passed, in part at least, from

the right to the left ventricle by filtration through the interposed septum.

Approaching the consideration of the quantity of blood that might pass through the heart by the arteries to the veins in a given interval of time, and the necessity of its circular motion in view of the amount proclaimed, Harvey now apologizes for what he finds himself forced, as it were, to say on the subject, which, indeed, is “of so novel a character, that he fears he may even have mankind for his enemies. His trust, however, is in the love of truth and the candour that inhere in cultivated minds "-words which deserve more careful consideration than they have ever received from the writers who maintain that the Circulation of the blood was even imagined, much less demonstrated, by any one of Harvey's predecessors. There cannot, indeed, be a question that the "Exercise on the Motion of the Heart and Blood" took the anatomical world by surprise; for the business of its leaders during a generation and more was to controvert the fact that was therein proclaimed, as an absurdity, not to ascribe it to this one or to that as an honour.

Revolving in his mind, then, what the quantity of blood might be that was transmitted by the heart, and in what interval of time its passage must be effected, "seeing that such an amount as presented itself could not be furnished by all the ingesta in the shape of meat and drink, without the veins on the one hand being drained, and the arteries on the other getting

filled to bursting, unless the blood should find its way from the arteries into the veins as fast as it was thrown by the heart into the arteries, and so return to the right ventricle whence it had started; "I began to think,” he says, “whether there might not be a motion in a circle, as it were." Then it was that the great truth flashed upon him; then it was that he saw that the blood, forced incessantly by the action of the left ventricle into the arteries and distributed by them to the body at large, must necessarily return by the veins to the right side of the heart; from thence be poured by the pulmonary artery into the lungs, reach the left auricle and ventricle by the pulmonary vein, be pumped again into the aorta and its branches, to return again and again to the heart and run the round as before.

"In this way it is," says the great physiologist, "that all parts of the body are nourished, cherished, and quickened by the warm, spirituous, more perfect, and truly alimentive blood; which then, cooled by contact with the parts, and become effete, returns to its sovereign, the heart, as its source, there to recover its pristine state of excellence, to receive a fresh infusion of native heat, to be impregnated anew with spirits, again to go forth replete with life-giving power, and all this accomplished by the action of the heart alone."

What an immense advance is this on all that had ever been said before on the motion of the heart and

blood? There is nothing to compare with it in simplicity and comprehensiveness in the whole range of antecedent anatomical literature. Well might the late eloquent Perpetual Secretary to the Academy of Sciences of Paris, M. Flourens, speak as he does of the "Exercise on the Motion of the Heart and Blood," as "a little work of no more than a hundred pages, but the very best book we have in physiology.""

To Harvey the arteries and veins only differed because of their distinct mechanical destinations; an artery being the vessel which carries the blood from the heart to the extreme parts of the body; a vein, the vessel which brings it back from the periphery to the centre; the artery thicker, stronger, resilient, as having to bear the shock of the heart, and help forward the successive waves; the vein thinner, and inelastic in its coats, having to support the weight of the column of blood returning to the heart. How much this swerves from the old, and, until Harvey's day, still accredited fancies about the diversity of structure between veins and arteries being destined to meet diversity in the subtlety, heat, charge of spirits, and other imaginary adjuncts to the several kinds of blood acknowledged, need not be said.

In the old physiology we have seen the motions of

1 "Ce petit livre de cent pages c'est le plus beau livre de Physiologie.” Hist. de la Découv. de la Circulation du Sang. 2me ed. The original of Harvey's "Anatomical Exercises" is all comprised in seventy-two pages small 4to.