Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/112

Rh 96 VASCULAR SYSTEM Discov ery of circula tion of blood. &quot; circulation,&quot; 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 Qusestiones Medicae, (lib. v., cap. 4, fol. 125), quoted by Gamgee, shows his views : &quot; The lungs, therefore, drawing the warm blood from the right ventricle of the htfart 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 sctnguinis 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 iiitromits ; the other lets out, the membranes (valves) being constituted accordingly.&quot; Still Cesalpinus 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 contractive and propulsive organ, and attributed the dilatation to &quot;an effervescence of the spirit,&quot; whilst the contraction, or, as he termed it, the &quot;collapse,&quot; was due to the appropriation by the heart of nutritive matter. Whilst he imagined a communication between the termina tion 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 re garded as the true discoverer of the circulation of the blood. More recently Ercolani has put forward claims on behalf of Carlo Ruini as being the true discoverer. Euini published the first edition of his anatomical writings in 1598, the year William Harvey entered at Padua as a medical student. This claim has been carefully investi gated by Gamgee, who has come to the conclusion that it cannot be maintained. 1 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 fibro-cartilaginous thickenings on the free edge of the semilunar valves (corpora Arantii). Hieronymus 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 flowed 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 ; and, 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, contain ing &quot; spirits &quot; 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 Harvey, was not until 1628 that Harvey announced his views to the world by publishing his treatise De Motu Cordis et Sanguinis (see vol. xi. pp. 503-504). His conclusions are given in the following celebrated passage : 1 Gamgee, &quot; Third Historical Fragment,&quot; in Lancet, 1876! &quot; And now I may be allowed to give in brief my view of the circu lation 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 ventricles, and is sent for distribution to all parts of the body, where it makes its way into the veins and pores of the flesh, and then flows by the veins from the circumference on every side to the centre, from lesser to the greater veins, and is by them finally discharged into the vena cava and right auricle of the heart, and this in such a quantity, or in such a flux and reflux, thither by the arteries, hither by the veins, as cannot possibly be supplied by the ingestor, and is much greater than can be required for mere purposes of nutrition, it is absolutely necessary to conclude that the blood in the animal body is impelled in a circle, and is in a state of ceaseless motion, that this is the act or function which the heart performs by means of its pulse, and that it is the sole and only end of the motion and contraction of the heart &quot; (bk. x. ch. xiv. p. 68). Opposed by Caspar Hofmann of Nuremberg, Yeslmgius of Padua, and J. Eiolanus the younger, this new theory was supported by Roger Drake, a young Englishman, who chose it for the subject of a graduation thesis at Leyden in 1637, by Rolfink of Jena, and especially by Descartes, and quickly gained the ascendant ; and its author had the satisfaction of seeing it confirmed by the discovery of the capillary circulation, and universally adopted. The cir- Capil- culation in the capillaries between the arteries and the lin y veins was discovered by Marcellus Malpighi (1628-1694) &quot; rcula of Bologna in 1661. He saw it first in the lungs and the mesentery of a frog, and the discovery was announced in the second of two letters, Epistola de Pulmonibus, ad dressed to Borelli, and dated 166 1. 2 Malpighi actually showed the capillary circulation to the astonished eyes of Harvey. Anthony van Leeuwenhoek (1632-1723) in 1673 repeated Malpighi s observations, and studied the capillary circulation in a bat s wing, the tail of a tadpole, and the tail of a fish. William Molyneux studied the circulation in the lungs of a water newt in 1683. 3 The idea that the same blood was propelled through the Transfe body in a circuit suggested that life might be sustained by of blo renewing the blood in the event of some of it being lost. About 1660 Lower, a London physician (died 1691), suc ceeded in transferring the blood of one animal directly from its blood-vessels into those of another animal. This was first done by passing a &quot; quill &quot; or a &quot; small crooked pipe of silver or brass &quot; from the carotid artery of one dog to the jugular vein of another. 4 This experiment was repeated and modified by Sir Edmund King, Coxe, Gayant, and Denys with such success as to warrant the operation being performed on man, and accordingly it was carried out by Lower and King on 23d November 1667, when blood from the arteries of a sheep was directly introduced into the veins of a man. 5 It would appear that the operation had previously been performed with success in Paris. The doctrine of the circulation being accepted, physiolo- Force o gists next directed their attention to the force of the heart, heart ar the pressure of the blood in the vessels, its velocity, and Qf 1 ^^ the phenomena of the pulse wave. Giovanni Alphonso Borelli (1608-1679) investigated the circulation during the Borelli. lifetime of Harvey. He early conceived the design of applying mathematical principles to the explanation of animal functions ; and, although he fell into many errors, he must be regarded as the founder of animal mechanics. In his De Motu Animalium (1680-85) he stated his theory of the circulation in eighty propositions, and in prop. Ixxiii., founding on a supposed relation between the bulk and the strength of muscular fibre as found in the ventricles, erroneously concluded that the force of the heart was qual to the pressure of a weight of 180,000 ft. He also 2 See his Opera Omnia, vol. i. p. 328. 2 Lowthorp, Abridgement of Trans. Roy. Soc., 5th ed., vol. iii. p. 230. 4 Ibid., p. 231. z Ibid., p. 226.