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Credit: Heart / by John Reid. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![its diastole, and not during its systole. This is ill reality what we would o priori expect, lor it certainly does at first appear somewhat uadoxical that the heart should strike tlie jianetes of the chest when the apex is ap- iproximated to the base. The concurrent tes- timony of the most accurate observers has, I however, fully established the correctness of '.the fact. Haivey observed it in the human !body when the heart had been exposed from ithe effects of disease.* One of the principal aarguments adduced in support of this opinion Iby these authors was drawn from the fact that ;the pulse at the wrist is not synchronous with ithe impulse against the chest, an opinion \-vvhich had been pretty generally maintained -since the time of Aristode. It is difficult to ibe convinced of this when the pulse is quick ; Ibut when it is slow, and in certain cases of i disease of the heart, it can generally be satis- t factonly ascertained. So far then they are right, i but in the next and most important step of the .argument they fall into a decided error; for ithey proceed upon the supposition that the 1 pulse is synchronous in all the arteries of the Ibody at the same time, and consequently the limpulse of the heart at the chest cannot be • synchronous with the flow of blood along the ; arteries, or, in other words, with the systole I of the heart. In opposition to this opinion. Dr. Youngt had previously shown upon the ] principles of hydraulics that the pulse along I the arteries must be progressive, yet in general : so rapid as to appear to arrive at the extremities I of the body without the intervention of any perceptible interval of time. And when the : attention of medical men was turned to this : subject, various observers soon ascertained by repeated experiments that the pulse could be felt in favourable cases to pass along the . arteries in a progressive manner, — that the pulse in the large arteries at the root of the neck and impulse at the chest are synchronous or nearly so, that both precede that at the wrist, and more distinctly still that of the dorsal artery of the foot.J Various attempts have been made to explain • Siraul nempe illud cordis ipsiiis motum observavimus, in diastole introrsnm siibduci et lelrahi; in systole vero emergere deniio et protrudi fierique in cprde systolem quo tempore diastole in carpo percipiebatur : atque propriiim cordis motum et funclionem esse systolem : denique cor tunc pectus fierique et prominulum esse cum erigitur sursum. As quoted by Shebeare, Pract. of Phy- sic, vol. j. p. 195. t Phil. Trans. 1809. j It is interesting and curious, as shewing the revolution of opinions, to compare the strict simi- larity of the arguments adduced by the modern supporters of this doctrine with those maintained by Shebeare in 1755. (Practice of Physic, vol. i. p. 193.) This, however plausible it may ap- pear, cannot be the true cause of it (impulse of the heart), because' then tliis stroke must be during the systole of the ventricles, which would be syn- chronous with the diastole of the arteries; whereas the beating of the heart precedes the dilatation of the arteries, and tlience this stroke must be made during the diastole of the ventricles : thus the diastole or distention of the heart is the cause of the beating against the ribs. HEART. ~ in what manner the apex of the heart is made to impinge against the parietes of the chest by those who maintain that it occurs during the systole of the ventricles. Senac supposed that this was principally effected by the curvature of the two large arteries, but principally of the aorta, which arise from the ventricles; for at each stroke of the ventricles when an addi- tional quantity of blood is driven into the large arteries, as they are curved they make an at- tempt to straighten themselves; and as this takes place to a slight extent, the heart, which is attached to their extremities, ought to be displaced, and its apex, which describes the arc of a circle greater than the other parts of the heart, is thus made to impinge against the walls of the chest. He also believed that the distention of the left auricle with blood during its diastole has also, from its position between the spine and base of the heart, the effect of pushing the heart forwards; and this occurring at the same time with the attempt which the curved arteries make to straighten themselves, it thus acts as a second or subsidiary cause in tilting the heart forwards.* Though this sup- posed effect of the curvature of the large arteries has been a favourite explanation with many of the impulse of the heart asainst the chest, yet it really appears to have little, if any, influence in producing this. Shebeare,t and, more lately, Dr. Corrigan,t have shown that the direction of the curvature of the large ar- teries is such, that if any effect of this kind is produced, the heart would not be carried to the left side, but in the direction of the curve, which is exactly in the opposite direction. Besides the tilting forwards of the heart has been observed though no blood was passing along the large vessels at the time, and the same thing takes place after the large vessels have been cut through and the heart removed from the body.§ Haller and others have sup- posed that the secondary cause assigned by Senac,—viz. the sudden distention with blood of the left sinus venosus which lies impacted between the spine and left ventricle,—is the principal if not the sole cause by which the heart is pushed forwards against the ribs. In confirmation of this opinion Haller states {| that if we inflate the left auricle after having opened the chest, we see the point of the heart approach with vivacity the region of the mam- ma. As we cannot, however, under these cir- cumstances distend the auricle without also distending the corresponding ventricle, this movement of the heart depends more upon the sudden inflation of the ventricle than upon any * Op. cit. torn. i. p. 356. The cause of the tilt- ing motion of the heart was also, at a later period, attributed to the curvature of the aorta and to this exclusively by Dr. W. Hunter. Note in Jolin Hun- ter's Treatise on Inflammation, p. 146, 1794. t 0(j. (it. p. 195. i Dublin Med. Trans, vol. i. p. 154. § Dr. Carson (Inquiry into the Causes of thr Motion of the Hlood, p. 183,) maintains that no proof can be adduced that the curvature of the aorta is rendered more straight during the systole of t^e heart. II Sur le Mouvcmcnt dn Sang, p. 124.](https://iiif.wellcomecollection.org/image/b21908503_0033.jp2/full/800%2C/0/default.jpg)
