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720 GESEEAL PATHOLOGY.

discover a marked pallor, soon followed by coldness of the skin. The
pulse becomes Meak, small in volume, and passes under the finger with
a peculiarly short and quick stroke, denoting an extreme relaxation of
the vascular system. The failure of the nervous system is seen in other
directions as well. Questions are answered slowly and hesitatingly, as
though not fairly understood ; the tone of the voice is changed, and
perhaps markedly enfeebled. The motions of the patient may show
sentences give place to monosyllables ; and the
extreme weakness ;
patient may sink into a state bordering u^Jon unconsciousness, in
which he takes no notice of what is going on around him. He may
recover from this condition speedily, with full restoration of the normal
tone and vigor of the nervous system, or recovery may be delayed
indefinitely. There is, however, generally a reaction within one or
two days.
In other cases all of the more profound symptoms of shock may
occur suddenly. Coma, or even death, may almost immediately follow
the receipt of a comparatively trifling injury or from mental impressions
that in other persons, and perhaps in the same person at another time,
would scarcely be noticed.
Shock differs materially from syncope. Emotion, the sight of a wound,
and various trifling circumstances may cause a momentary stoppage of
the action of the heart, with a temporary loss of consciousness, and not
be productive of shock. The production of shock evidently involves
some other factor, for instead of a temporary arrest of function there
appears to be a real injury to the structure upon which the functioning
poAver depends that renders immediate recovery impossible. Time must
be had for recovery from this tissue injury, and during this period these
functions are imperfectly performed, apparently from lack of power.
The symptoms seem to point to the failure of those nerve-centres that
maintain the proper tension of the vascular system. Normally, the
walls of the arteries are contracted upon the blood they contain, so as
to keep up a certain degree of arterial pressure, this being to a lesser
extent complemented by the veins. In shock there is a sudden letting
go of this tension, of this grasp on the blood. The vascular system is
relaxed abnormally, and in such a manner as to interfere with the cir-
culation. At the same time there is a relaxation of the energies of the
heart, but not a stoppage as in syncope, except it be in some of those
grave forms that result in almost instant death, in which this point can-
not Avell be studied and distinguished from other symptoms. The rule
is that the heart maintains its action, but in a very feeble way ; and it
appears to have been shown by experiment on the frog that even Avhen
the heart is stop]")ed it may be induced to resume its action by supplying
it M'ith blood. Prof. Goltz of Strasbourg j^erformed the experiment in
this way A frog was suspended in a vertical position with the legs
:
hanging down and the heart exposed. After a few moments' delay, to
see that the circulation was going forward normally, the animal was
struck a smart blow on the surface of the abdomen. The heart stopped
its contractions at once, and af^er a few moments began again feebly,
but it was clear that it was propelling no blood into the aorta, for the
upper part of the vena cava was empty and no blood was supplied to