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Rh Harvey entered at Padua as a medical student. This he studied its structure, pointing out the fibrous rings at -the bases of the ventricles; he showed that its wall consists of layers of fibres connected with the fibrous rings; and he described these layers as being of three kinds-straight or vertical, oblique, and circular or transverse. From the disposition of the fibres he reasoned as to the mechanism of the contraction and relaxation of the heart. He supposed that the relaxation, or diastole, was accounted for principally by the longitudinal fibres contracting so as to draw the apex towards the base, and thus cause the sides to bulge out; whilst the contraction, or systole, was due to contraction of the transverse, or oblique fibres. He showed that the pores of Galen, in the septum between the ventricles, did not exist, so that there could be no communication between the right and left sides of the heart, except by the pulmonary circulation. He-also investigated minutely the internal structure of the heart, describing the valves, the columnae carneae and the musculi pop ill ares. He described the mechanism of the valves with much accuracy. He had, however, no conception either of a. systemic or of a pulmonary circulation. To him the heart was a reservoir. from which the blood ebbed and flowed, and there were two kinds of blood, arterial and venous, having different circulations and serving different purposes in the body. Vesalius was not only a great anatomist: he was a great teacher; and his pupils carried on the work in the spirit of their master. Prominent among them was Gabriel Fallopius (1523–1562), who studied the anastomoses of the blood vessels, without the art of injection, which was invented by Frederick Ruysch (1638–1731) more than a century later. Another pupil was Columbus (Matthieu Reald Columbo, ob. 1560), first a prosector in the anatomical rooms of Vesalius and afterwards his successor in the chair of anatomy in Padua; his name has been mentioned as that of one who anticipated Harvey in the discovery of the circulation of the blood. A study of his writings clearly shows that he had no true knowledge of the circulation, but only a glimpse of how the blood passed from the right to the left side of the heart. In his work there is evidently a sketch of the pulmonary circulation, although it is clear that he did not understand the mechanism of the valves, as Vesalius did. As regards the systemic circulation, there is the notion simply of an oscillation of the blood from the heart to the body and from the body to the heart. Further, he upholds the view of Galen, that all the veins originate in the liver; and he even denies the muscular structure of the heart. In 1553 Michael Servetus (1511–1513), a pupil or junior fellow-student of Vesalius, in his Christianismi Restitutio, described accurately the pulmonary circulation. Servetus perceived the course of the circulation from the right to the left side of the heart through the lungs, and he also recognized that the change from venous into arterial blood took place in the lungs and not in the left ventricle. Not so much the recognition of the pulmonary circulation, as that had been made previously by Columbus, but the discovery of the respiratory changes in the lungs constitutes Servetus's claim to be a pioneer in physiological science.

Andrea Cesalpino (1519–1603), a great naturalist of this period, also made important contributions. towards the discovery of the circulation, and in Italy he is regarded as the real discoverer Cesalpino knew the pulmonary circulation. Further, he was the first to use the term “circulation,” and he went far to demonstrate the systemic circulation. He experimentally proved that, when a vein is tied, it fills below and not above the ligature. The following passage from his Quaestiones Medicae (lib. v. cap. 4, fol. 125), quoted by Gamgee, shows his views:—

“The lungs, therefore, drawing the warm blood from the right ventricle of the heart through a vein like an artery, and returning it by anastomosis to the venal artery (pulmonary vein), which tends towards the left ventricle of the heart, and air, being in the meantime transmitted through the channels of the aspera arteria (trachea and bronchial tubes), which are extended near the venal artery, yet not communicating with the aperture as Galen thought, tempers with a touch only. This circulation of the blood (huic sanguinis circulationi) from the right ventricle of the heart through the lungs into the left ventricle of the same exactly agrees with what appears from dissection. For there are two receptacles ending in the right ventricle and two in the left. But of the two only one introits; the other lets out, the membranes (valves) being constituted accordingly.”

Still Cesalpino clung to the old idea of there being an efflux and reflux of blood to and from the heart, and he had confused notions as to the veins conveying nutritive matter, whilst the arteries carried the vital spirits to the tissues. He does not even appear to have thought of the heart as a contractile and propulsive organ, and attributed the dilatation to “an effervescence of the spirit,” whilst the contraction—or, as he termed it, the “collapse”—was due to the appropriation by the heart of nutritive matter. Whilst he imagined a communication between the termination of the arteries and the commencement of the veins, he does not appear to have thought of a direct flow of blood from the 'one to the other. Thus he cannot be regarded as the true discoverer of the circulation of the blood. More recently Ercolani has put forward claims on behalf of Carlo Rumi as being the true discoverer. Ruini published the first edition of of his anatomical writings in 1598, the year William claim has been carefully investigated by Gamgee, who has come to the conclusion that it cannot be maintained.

The anatomy of the heart was examined, described and figured by Bartolomeo Eustacheo (c. 1500–1574) and by Julius Caesar Aranzi or Arantius (c. 1530–1589), whose name is associated with the libro-cartilaginous thickenings on the free edge of the semilunar valves (corpora Arantii). Hicronymus Fabricius of Acquapendente (1537–1619), the immediate predecessor and teacher of Harvey, made the important step of describing the valves in the veins; but he thought they had a subsidiary office in Connexion with the collateral circulation, supposing that they diverted the blood into branches near the valves; 'thus he missed seeing the importance of the anatomical and experimental facts gathered by himself. At the time when Harvey arose the general notions as to the circulation may be, briefly summed up as follows: the blood ebbed and Howed to and from the heart in the arteries and veins; from the right side at least a portion of it passed to the left side through the vessels in the lungs, where it was mixed with air; land, lastly, there were two kinds of' blood-the venous, formed originally in the liver, and thence passing to the heart, from which it went out to the periphery by the veins and returned by those to the heart; and the arterial, containing “spirits” produced by the mixing of the blood and the air in the lungs—sent out from the heart to the body and returning to the heart by the same vessels. The pulmonary circulation was understood so far, but its, relation to the systemic circulation was unknown. The action of the heart, also, as a propulsive organ was not recognized. It was not until 1628 that Harvey announced his views to the world by publishing his treatise De Motu Cordis et Sanguinis. His conclusions are given in the following celebrated passage:—

“And now I may be allowed to give in brief my view of the circulation of the blood, and to propose it for general adoption.Since all things, both, argument and ocular demonstration, show that the blood passes through the lungs and heart by the auricles and