doubtless to accommodate each order of spirits with its own particular officine or workshop. With the revival of anatomical knowledge in modern Europe, however, the partition of the ventricles was soon perceived not to be porous or cribriform, but, as was first said, to be so nearly solid that any filtration of blood through it was well nigh impossible (Berengarius, 1521), and next, to be so completely solid that all permeation of blood was impossible (Vesalius, 1555), and another means must therefore be found for securing the necessary admixture of the two kinds of blood in order to effect the engenderment of the natural, animal, and vital spirits.
Such was the state of anatomical science and physiological belief on this particular point when Michael Servetus came upon the stage, and suggested the transit of the blood through the lungs from the right side of the heart to the left, with a view of meeting the difficulty which the undeniable solidity of the septum ventriculorum opposed to the presumed necessary admixture of the two kinds of blood. Servetus’s idea, consequently—if at the distance of three hundred years we may presume to follow the mental process that led to the penning of the remarkable and often-quoted passage which occurs in his works—appears to be nothing more than a suggestion or proposition as a means of meeting a difficulty; it is very much as though he had said: If you cannot go straight through, you must even go round about. To so much and to no more, do Servetus’s claims to be considered a discoverer, in the sense we would attach to that word, amount. The passage from the ‘Restitutio Christianismi’ of Servetus, 1553, if viewed from the point proposed, will not fail to set his title to be regarded as the discoverer of the lesser circulation in its true light—in a light under which it has not yet been seen. We translate so much of the passage as bears on the question under review. “The vital spirit has its origin in the left ventricle, the lungs assisting especially in its generation. It is a subtile spirit * * * It is engendered from the mixture that takes place in the lungs of the inspired air with the elaborated subtile blood which the right ventricle of the heart communicates to the left. But this communication takes place, not by the middle septum of the heart, as is commonly believed, but by a remarkable artifice; the subtile blood of the right side of the heart is agitated in a lengthened course through the lungs, whereby it is elaborated, from which it is thrown of a crimson colour, and from the vena arteriosa (pulmonary artery) is transfused into the arteria venosa (pulmonary veins); it is then mixed in the arteria venosa itself with the inspired air, and by the act of expiration is purified from fuliginous vapours, when, having become the fit recipient of the vital spirit, it is at length attracted by the diastole. Now, that the communication and preparation take place as stated through the lungs, is proclaimed by the various conjunctions and communications of the arterial vein with the venous artery. The remarkable size of the arterial vein (pulmonary artery) confirms this, a vessel which could neither have its actual constitution nor dimensions, nor transmit such a quantity of the purest blood direct from the heart itself, for the mere nourishment of the lungs. Neither would the heart supply the lungs in such proportion, (especially when we see the lungs in the embryo nourished from another source) by reason of those membranes or valves which remain unopened until the hour of birth, as Galen teaches. The blood, consequently, from the moment of birth, is sent, and in such quantity is sent, for another purpose from the heart into the lungs; from the lungs also it is not simple air that is sent to the heart, but air mixed with blood is transmitted through the arteria venosa (pulmonary vein). In the lungs consequently does the mixture take place. The crimson colour is imparted to the spirituous blood by the lungs, not by the heart. There is not room enough in the left ventricle of the heart for so important and so great an admixture; neither is there space there for the elaboration into the crimson colour. Finally, the septum medium, seeing that it is without vessels and properties, is not adapted to accomplish that communication and elaboration, although something may transude through it.”
The discussion in this passage from Servetus obviously concerns the generation of the vital spirit, not the pulmonic circulation properly so called—that is altogether secondary and subordinate. His mention of “numerous communications between the vena arteriosa and the arteria venosa,” is plainly conjectural; neither he, nor any one else for a century after him, saw such communications. The course through the lungs, then, as suggested by Servetus, was a mere hypothetical proposal for getting over the difficulty of the solid, or nearly solid, septum ventriculorum. As to the means by which such a transfusion as he suggests, is effected, Servetus, as he was profoundly ignorant himself, so does he leave his readers entirely in the dark. The transmission of the blood from the right to the left side of the heart, which Servetus proposed, is in fact, no great improvement on the old efflux and reflux, like the tides of Euripus, betwixt Attica and Eubœa. He had no conception of a circle of the blood beginning and ending in the heart. On the contrary, he regarded the liver as the fountain-head of the blood; and if he has any reference to a moving power in connexion with the heart, it is nothing more than the diastole or dilatation of the organ that is named—a passive state therefore considered as an active and efficient cause, which is absurd.
The first modern anatomist of high repute, who treats particularly of the motion of the blood, may be said to be Realdus Columbus;[55] for Servetus, though educated to the medical profession, had long forsaken it for divinity, and only uses his old anatomical knowledge as a means of illustrating a theological dogma. Columbus, in treating of the heart and lungs, has certainly much that is remarkable, and much that is true; and had he said nothing more than we find in single detached sentences or paragraphs of his book, he must have been regarded as having gone a great length in the right direction. The blood, he says, once it has entered the right ventricle from the vena cava, can in no way again get back; for the tricuspid valves are so placed that whilst they give a ready passage to the stream inwards, they effectually oppose its return. The blood continuing to advance from the right ventricle into the vena arteriosa or pulmonary artery, once there cannot flow back upon the ventricle, for it is opposed by the sigmoid valves situate at the root of the vessel. The blood, therefore, agitated and mixed with the air in the lungs, and having thus in some sort acquired the nature of spirit, is carried by the arteria venosa or pulmonary vein into the left ventricle, from whence, being received into the aorta, it is, by the ramifications of this vessel, transmitted to all parts of the body.
This much taken by itself looks very like an exposition of the circulation of the blood as understood at the present time, though we still see that the blood must be made to participate in the nature of spirit before it enters the arteries, and is not the blood which is contained in the veins, and which nourishes the body; but when we go farther and turn to other parts of his writings, we see that Columbus could never have conceived any proper idea of the circulation. For example, he continues, with Galen, to regard the liver as the origin of all the veins. The vena portæ, he says, arising by innumerable roots from the concavity of the liver, proceeds to carry blood from this organ by different branches to the stomach, spleen, and intestines, to the end that it may convey nourishment in the first case, black bile in the second, and in the third serve a double function—viz. supply nourishment to the intestines at once, and by a kind of imbibition, obtain nutritive matter, which is forthwith sent back to the liver for elaboration into blood. The vena cava again, he describes as arising from the convex aspect of the liver, whence, by its ramifications, it carries the blood that is requisite to nourish and maintain every part of the body.
This of itself is enough. But when, in addition, we find that Columbus denies the muscular nature of the heart, we are fully qualified to form a true estimate of the conception which he could have had of the motion of the blood, and of his right to be regarded as the discoverer of its ceaseless circular movement.
The next who is brought upon the scene with the imputed honour of having had a knowledge, not only of the lesser, but of the greater or systemic circulation also, is Andreas Cæsalpinus,[56] of Arezzo. The account which this celebrated peripatetic philosopher gives of the passage of the blood from the right to the left side of the heart is essentially the same as that given by Columbus. From the right ventricle the blood passes into the pulmonic artery, and from this, by numerous anastomoses, into the pulmonic veins, which transmit it to the left ventricle. Cæsalpinus says well that it is absurd to call the pulmonary artery by the name of vena arteriosa, on the mere ground of its taking its departure, like the vena cava, from the right ventricle;
