Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit25760/613/
HEART. 
its diastole, and not during its systole. This 
is in reality what we would à priori expect, 
for it certainly does at first appear somewhat 
paradoxical that the heart should strike the 
parietes of the chest when the apex is ap¬ 
proximated to the base. The concurrent tes¬ 
timony of the most accurate observers has, 
however, fully established the correctness of 
the fact. Harvey observed it in the human 
body when the heart had been exposed from 
the effects of disease.* One of the principal 
arguments adduced in support of this opinion 
by these authors was drawn from the fact that 
the pulse at the wrist is not synchronous with 
the impulse against the chest, an opinion 
which had been pretty generally maintained 
since the time of Aristotle. It is difficult to 
be convinced of this when the pulse is quick ; 
but when it is slow, and in certain cases of 
disease of the heart, it can generally be satis¬ 
factorily ascertained. So far then they are right, 
but in the next and most important step of the 
argument they fall into a decided error; for 
they proceed upon the supposition that the 
pulse is synchronous in all the arteries of the 
body at the same time, and consequently the 
impulse of the heart at the chest cannot be 
synchronous with the flow of blood along the 
arteries, or, in other words, with the systole 
of the heart. In opposition to this opinion, 
Dr. Youngf had previously shown upon the 
principles of hydraulics that the pulse along 
the arteries must be progressive, yet in general 
so rapid as to appear to arrive at the extremities 
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.I 
Various attempts have been made to explain 
* “ Simul cordis ipsius motum observavimus, 
nempe illud in diastole introrsum subduci et 
retrain ; in systole vero emergere denuo et protrudi 
fierique in corde systolem quo tempore diastole in 
carpo percipiebatur : atque proprium cordis motum 
et functionem esse systolem : denique cor tunc 
pectus fierique et prominulum esse cum erigitur 
sursum.” As quoted by Shebeare, Pract. of Phy¬ 
sic, vol. i. p. 195. 
t Phil. Trans. 1809. 
£ 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 this 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 thence 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.” 
605 
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 against the 
chest, yet it really appears to have little, if any, 
influence in producing this. Shebeare,f and, 
more lately, Dr. Corrigan, + 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. tom. 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 John Hun¬ 
ter’s Treatise on Inflammation, p. 146, 1794. 
t Op. cit. p. 195. 
t Dublin Med. Trans, vol. i. p. 154. 
$ Dr. Carson (Inquiry into the Causes of the 
Motion of the Blood, p. 183,) maintains that no 
proof can be adduced that the curvature of the 
aorta is rendered more straight during the systole 
of the heart. 
|| Sur le Mouvement du Sang, p. 124.
        

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