dilatation of the artery by the contraction of the heart, which is the truth.
Galen also taught that there are two kinds of blood, the spiritual blood of the arteries and left ventricle, and the venous blood of the right side of the heart and veins, the red and the black blood. These were great strides in the right direction, and yet this wonderful genius was the author of some grave errors. He believed it necessary that a certain portion of spirit should be mixed with the venous blood to render it fit for nutrition, and this he conceived took place by the transmission of arterial blood through little holes in the ventricular septum which he called "foramina." He taught that the arterial blood nourished organs of a light and delicate texture such as the lungs, while the venous blood nourished the grosser organs, such as the liver.
The early modern anatomists believed the septum was perforated, and saw with the eyes of faith the "foramina" on account of their unquestioning confidence in the infallibility of Galen as an authority. Mondinus, who flourished in the fourteenth century, the first anatomical writer after Galen, said the septum was perforated, and twenty others reiterated it.
Berrenger de Carpi, who wrote and published his anatomical work in 1521, was the first to waver, and say that the openings in the septum were only to be seen with difficulty.
That I may pass no one who has been credited by any writer with even the least knowledge of the circulation, or who has even hinted a better understanding of it than those already mentioned, I come next in the order of time to Nemesius, who was Bishop of Emissa, a city of Phœnicia, at the latter end of the fourth century. He was not properly a medical writer, though he wrote a treatise concerning the "Nature of Man." The editor of the Oxford edition of this work (1671) contends that Nemesius understood and described the circulation of the blood in plain terms; while Dr. Freind, in his "History of Physic," denies that he had anything more than a vague notion of this function. I copy the words of Nemesius as translated by Freind for the benefit of the curious:
"The motion of the pulse takes its rise from the heart, and chiefly from the left ventricle of it; the artery is with great vehemence dilated and contracted, by a sort of constant harmony and order. While it is dilated, it draws the thinner part of the blood from the next veins, the exhalation or vapor of which blood is made the aliment for the vital spirit. But, while it is contracted, it exhales whatever fumes it has through the whole body, and by secret passages. So that the heart throws out whatever is fuliginous, through the mouth and the nose by expiration."
Thus it appears that Nemesius had a little insight of the circulation 1,500 years ago, yet so imperfect that he neither comprehended it himself nor made it understood by any who followed him.
