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.