the capillaries first, from an experiment in which
the brain or spinal marrow was crushed : an
effect was observed upon the circulation in the
capillaries, similar to what is observed in the
heart under similar circumstances ; the capillary
circulation, like the beat of the heart, was immediately
arrested or impaired. But most conclusive
objections are opposed to this experiment.
1. The influence of the heart itself is not removed.
It is true Dr. Philip argues that the effect of the
experiment in destroying the action of this organ,
cannot influence its result, because to remove the
heart altogether is said not immediately to change
the condition of the circulation in the web of the
frog. Dr. Philip’s account of the experiment is
as follows :—“ The web of one of the hind legs
of a frog was brought before the microscope and
while Dr. Hastings observed the circulation, which
was vigorous, the brain was crushed by the blow
of a hammer. The vessels of the web instantly
lost their power, the circulation ceasing; an effect
which cannot arise, we have seen, from the ceasing
of the action of the heart. In a short time, the
blood again began to move, but with less force.
This experiment was repeated with the same resuit.”
1 Whether this argument be well founded,
or not, I leave to the judgment of the reader, after
he shall have perused the detail of the experiment
of the removal of the heart, given page 66,—an
experiment witnessed by at least four competent
judges. 2. The influence of the arteries, which
we have proved to possess a contractile power,
was not separated from that of the capillaries,
with regard to which the question remains to
be determined. There is no circumstance in the
experiment to determine which set of vessels, the
arteries, the capillaries, or even the veins, were
affected by the experiment. 3. The capillary circulation
was also left subject to the influence of
contraction in the whole muscular system. This
is thrown into spasmodic action by the act of
violence inflicted upon the nervous masses ; by
this action of the muscles, the veins are compressed,
and the circulation in the capillaries is
mechanically arrested. The result is one of the
most complex and equivocal kind, and utterly
incapable of determining the question of a muscular
action in the capillary vessels themselves
considered separately and distinctly.
1 On the Vital Functions; p. 81.