THE PUNGCTIONS OF THE VISCERAL NERVES 95 
It may appear almost incredible that such extremely mild galvanic currents, 
applied through the spinous processes of the posterior dorsal region, should 
be capable of thus affecting the heart ; but that their effects were really very 
considerable, was clear from the further progress of this experiment, and from 
others somewhat similar, which showed that this apparently trivial stimulation 
eradually exhausted the part of the nervous system through which the heart 
is acted on by the cord. Thus, in one case, currents only just perceptible to the 
tongue, transmitted for about thirty seconds at a time through the lower cervical 
and upper dorsal regions of the spine, at intervals of nine minutes on the average 
during two hours and twenty minutes, produced at first decided increase of the 
heart’s action, but during the last hour failed to affect it at all. The strongest 
possible action of the battery which, as proved by other experiments, would, 
at the outset, have entirely arrested the cardiac movements, was then set on, 
but with no effect whatever on the organ. 
When partial exhaustion has occurred, a much stronger galvanic stimulus 
is required, to produce the same effect upon the heart, than at the commence- 
ment of an experiment; and thus an action of the battery which, when first 
applied, causes marked diminution in the number of beats, may after a while 
come to have the opposite effect, and increase the heart’s action as decidedly 
as it had previously lowered it ; while at an intermediate period it may seem 
to have no influence at all. This principle gives the clue to understanding 
what had before appeared incomprehensible in these experiments, showing that 
facts, which at first seemed utterly inconsistent, were really perfectly harmonious. 
The case before related, in which revival of the heart’s action resulted from 
powerful stimulation of the vagus, which, had the organ been contracting as 
usual, would have arrested its movements and probably finally destroyed them, 
will now be understood. I have seen other analogous cases of revival of action 
by very powerful galvanism, which under ordinary circumstances would have 
arrested it, viz. twice in the heart and twice in the intestines. The observation 
published so long ago as 1839 by Valentin,! that mechanical or chemical irritation 
of the vagus in the neck of an animal recently dead, and with the nerves conse- 
quently enfeebled, causes contraction of the ventricles, admits of a similar 
interpretation, as also does a corresponding fact regarding the splanchnic nerves, 
given without explanation by Kupfer and Ludwig, in a paper just published,” 
viz. that they lose their inhibitory influence a certain time after death, and 
acquire a motor power over the intestines. 
Two more experiments require mention, as they exclude the possibility of 
* Valentin, De Functionibus Nervorum, p. 62. 
* Henle and Pfeufer’s Zeztschrift, 3rd series, vol. ii, part 3. 
