that from experiment. Both Haller 1 and Spallanzani
2 performed the experiment of the excision
of the heart, observing the subsequent condition
of the circulation. Their account of this experiment
is, however, in my opinion, very unsatisfactory.
I resolved, therefore, to repeat it
carefully, carefully observing the results. This I
did thrice.
A ligature was applied round the aorta of a
frog. The circulation in the web, which was
previously very vigorous, was almost immediately
arrested, first in the capillaries, then in the veins.
In the arteries there was a singular oscillatory
movement of the blood for ten or fifteen minutes.
The globules of blood proceeded slowly onward for
some seconds ; there was then, all at once, a
rapid retrograde movement of the blood apparently
through the same space. This oscillation
was repeated: the globules of blood were again
moved alternately in progressive and retrograde
directions as before.
It appeared to me that the artery gradually
contracted, in successive portions, and slowly
1 Deux Mémoires, &e. pp. 304—306.
2 Expériences sur la Circulation, &c. p. 327, &c.
emptied itself by propelling the blood in a continued
stream along its final branches : that it
then dilated suddenly, and drew the globules of
blood in a rapid retrograde course.
During the first contraction of the artery, the
blood would be propelled along the capillaries
and veins. During the succeeding contractions
and relaxations of the artery, the globules would
merely oscillate, being driven forwards and drawn
backwards alternately.
From these observations, it would appear almost
certain that the arteries possess a muscular
contractile power.
Another argument for the contractile power
of the arteries, arises from a view of their anatomical
structure. The structure of the arteries
has been so skilfully displayed, and the argument
flowing from it so beautifully deduced, by Mr.
Hunter, that I must refer to the well-known work
of that extraordinary man for full and satisfactory
information on this point.
A further argument for the contractile influence
of the arteries is particularly noticed by Laënnec.
Speaking of augmented impulse in particular arteries,
he observes :— lt Ce phenomène est un de ceux