vapors by the act of expiration, the mixture being now complete in every respect, and the blood become fit dwelling-place of the vital spirit, it is finally attracted by the diastole, and reaches the left ventricle of the heart." He then goes on to give as proofs of the accuracy of his statements (1) the various conjunctions and communications of the pulmonary artery and pulmonary vein in the lungs, and (2) the great size of the pulmonary artery, and the great quantity of blood passing through it; both being much larger than would be required for the mere nutrition of the lungs. He concludes that the septum, seeing that it is without vessels and special properties, is not fitted to permit the communication in question, "although," he adds, "it may be that some transudation takes place through it."[1] This unfortunate qualification of what he has so distinctly affirmed just before namely, that the communication does not take place through the septum is not very intelligible; for if he believed the blood to soak through the septum, his theory differs but little from that of Galen, and yet Servetus calls attention to the fact that what he is declaring was unknown to Galen.[2]
Prof. Huxley[3] points out that Servetus quotes neither observation nor experiment in favor of the imperviousness of the septum. But neither does Realdus Columbus,[4] who correctly described the lesser circulation in 1559, and to whom the credit of the discovery was very early ascribed.[5] It is to be remembered that the work in which Servetus introduces his discovery is not a treatise on physiology, and that the whole passage being brought in by way of illustration is not fully treated.
It is clear, however, that Servetus held (1) that the blood in a great stream passes from the right ventricle of the heart to the lungs; (2) that in the lungs, and not in the left ventricle, it is purified; and (3) that from the lungs it passes by the pulmonary vein to the left ventricle of the heart and thence into the arteries.
From these statements of fact Servetus quickly passes to metaphysical speculations. He has before said: "There are three sorts of spirits in the human body—namely, natural, vital, and animal—which are not in reality three, but two distinct spirits only; the arteries communicating by anastomoses, the vital spirit to the veins, in which it is called natural. The first spirit then is the blood, whose seat is in the liver, and in the veins of the body; the second is the vital spirit, whose seat is the heart and arteries; the
