Bauhaus-Universität Weimar

THE SYSTOLE AND DIASTOLE. 
185 
that of the ventricles not being synchronous. In warm-blooded 
animals the auricles contract immediately before the ventricle. In 
the frog the contractions of the venous trunks, of the auricles, the 
ventricle, and the bulbus aortæ, appeared to me to follow the order 
in which I have specified the parts, the intervals between the four 
contractions being nearly equal; so that the same interval of time 
elapsed from the contraction of the auricles to the contraction of the 
ventricle, as between the contraction of the ventricle and that of the 
bulb of the aorta. I am convinced, from repeated observations, that 
the auricles and ventricle do not, as Oesterreicher* asserts, alternate 
in action at equal intervals, like the motions of the pendulum, but 
that the time that intervenes between the contraction of the auricles 
and the contraction of the ventricle is much less than that which 
elapses from the moment of the contraction of the ventricle to the 
moment when the auricles again act; and that generally the con¬ 
traction of the bulbus aortæ and venous trunks occur in the interval 
of time last indicated. In warm-blooded animals I have seen the 
contractions of the auricles cease altogether for some moments, 
which must have been caused by the injury inflicted in making the 
observation. Under ordinary circumstances, the auricular contrac¬ 
tion was always a very quick motion immediately preceding the 
action of the ventricle, the interval of time from the contraction of 
the auricles to the contraction of the ventricle being certainly very 
much shorter than the period that elapsed between the contraction 
of the ventricles and that of the auricles. 
The contraction (systole) alone of the heart is an active state; the 
dilatation (diastole) is the moment of repose, in which the fibres are 
relaxed, and in which the blood is poured from the contiguous veins 
into the cavities of the heart, to fill the vacuum consequent on the 
relaxation of its fibres: the valves of the heart being so arranged as 
to allow the influx of the blood from the veins. The dilatation of 
the heart was supposed by Bichat, and some other French physiolo¬ 
gists, to be an active movement, but Oesterreichert has by a very 
ingenious experiment refuted this supposition. He removed the 
heart of a frog from the body, and laid upon it a substance sufficiently 
heavy to press it flat, and yet so small as not to conceal the heart 
from view; he then observed that during the contraction of the heart 
the weight was raised, but that during its dilatation the heart re¬ 
mained flat. This experiment shows that the dilatation of the heart 
is not a muscular act; at the same time, however, it must be recol¬ 
lected that the walls of the heart during life cannot become so relaxed 
at the time of the diastole, as in a heart removed from the body, even 
although the cavities of the heart were not filled with blood; for, in 
the living state, the capillary vessels of its substance are at the time 
of relaxation injected with blood, which, during the contraction, is 
pressed out of them, and this filling of its vessels must give it some 
degree of firmness and rigidity. 
* Lehre vom Kreislauf des Blutes. Nürnb. 1826. 
f Loc. cit. p. 33. 
16*
        

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