Chapter VII (3)

When two ligatures are applied at the same time and at some
centimetres distant upon two points of an artery which furnishes
no branches, we have a portion of artery in which the blood is
subjected only to the influence of the parietes. If we make in
this portion of the vessel a small opening, almost all the blood
that it contains is immediately thrown out, and the artery is much
contracted. This experiment has been known for a long time, and
uniformly succeeds. The following is one of my own, and places,
it seems to me, the phenomenon in a very clear light. I laid bare
the crural artery and vein of a dog to a certain extent; I passed
under these vessels, near the trunk, a string, which I afterwards
drew tightly at the posterior part of the thigh, so that all the
arterial blood should come to the limb by the crural artery, and
all the venous blood return to the trunk by the crural vein; I then
applied a ligature upon the artery, and this vessel was very soon
completely empty in the part below the ligature.

It is then satisfactorily proved that the force with which the
arteries contract upon themselves is sufficient to expel the blood
they contain. But what is the nature of this contraction? We have
proved that it cannot be attributed to irritability. Every thing
leads to the belief that it should be referred to the very great
elasticity which the arterial parietes enjoy, an elasticity that
is brought into action, when the heart forces a certain quantity
of blood into the cavity of these vessels. This property of the
arteries being known, it is easy to conceive how the principal
agent of the arterial motion, being alternate, the course of fluid
is yet continuous. The elasticity of the arterial parietes is
similar to that of the reservoir of air in certain pumps with an
alternate action, and which notwithstanding throw out the fluid in
a continuous manner.

It is not enough to know the kind of influence which the
contraction of the arteries has on the motion of the arterial
blood; it is necessary to know if this contraction does not
influence in a sensible manner the course of the blood in the
veins. This is elucidated by the following experiment. Lay bare,
as in the preceding experiment, the crural artery and vein of
a dog; tie the limb strongly, taking care not to include these
vessels; afterwards tie the crural vein, and make a small opening
in it below the ligature, of one or two lines in length; the blood
flows out in a continuous jet. If the artery be compressed, so as
to intercept the course of blood in it, the jet still continues
a short time; but it is seen sensibly to diminish, as the artery
is becoming empty. It at length ceases entirely when the artery
is completely emptied; and though the vein remains distended
with blood along its whole extent, it does not flow out at the
small wound. If the compression be taken off of the artery, the
blood enters it with force, and almost at the same instant it
begins again to flow from the opening in the vein, and the jet is
reestablished as before. If we check the course of the blood in the
artery, there is but a feeble jet from the vein; it is the same if
the passage of this fluid is alternately intercepted and permitted.

I make the same phenomenon evident in another way; I introduce into
the crural artery the extremity of a syringe filled with water at
the temperature of 30 degrees of the centigrade thermometer; I push
the piston slowly, and soon the blood goes out by the opening in
the vein, at first alone and afterwards mixed with water, and it
forms a jet the more considerable in proportion to the force with
which the piston is pushed.

To prove, as we have done, that the heart maintains an evident
influence on the course of the blood in the capillary vessels, is
not to advance that these vessels have no action on the motion of
this fluid. Many physiological phenomena, on the contrary, prove
that the capillaries can aid with more or less facility the passage
of the blood, and consequently sensibly influence its course.

[34] Under no circumstance does the stomach rise up, as Bichat
calls it. We have, in a preceding note, explained the ordinary
motions of this viscus, in a state of vacuity, during digestion and
under the influence of an internal or external stimulus. None of
these motions are sufficient to produce that sudden and energetic
expulsion which characterizes vomiting. The opinion that the
stomach rises up in vomiting originated in a time of ignorance,
and we ought not to be astonished that it should find advocates
even in our day. This has not however been uniformly adopted; Bayle
and P. Chirac opposed it by experiments; Senac, Van Swieten and
Duverney declared themselves against it; but Haller, by adopting
it, suddenly changed the views and removed the uncertainty of a
great number of physiologists, who, not taking the labour of making
experiments for themselves, loved to repose on the faith of a
celebrated name. In physiology the opinions of Haller are certainly
entitled to very great weight; this is because this wise observer,
before announcing them as a general proposition, was accustomed to
repeat many times the experiments on which he founded them; but in
this case he did not sufficiently question the use of the stomach
in vomiting.

He has made four experiments only, less for the purpose of
satisfying himself that the phenomenon existed, than to see it such
as he supposed it. It is very difficult, even for the best mind,
to divest itself in observing, of the ideas previously received
without examination. It may then be believed, that Haller in this
way saw but superficially. These considerations determined me some
years since, to satisfy myself of what takes place in vomiting,
and of the part which the stomach performs in it. I shall relate
briefly the experiments which I tried on the subject. The first
was made on a dog of middling size, whom I had made to swallow six
grains of emetic. When this medicine had excited nausea, I cut
through the linea alba opposite the stomach, and introduced my
finger into the abdomen. At each nausea, I felt it very powerfully
compressed above by the liver, which the diaphragm pushed down, and
below by the intestines, which were compressed by the abdominal
muscles. The stomach also appeared to me to be compressed; but
instead of feeling it contract, it appeared to me, on the contrary,
to increase in size. The nauseas became more frequent, and the more
marked efforts, which precede vomiting, appeared. Vomiting finally
took place, and then I felt my finger pressed with a force truly
extraordinary. The stomach rid itself of a part of the aliments it
contained; but I distinguished no sensible contraction in it. The
nausea having ceased for a short time, I enlarged the opening in
the linea alba, for the purpose of observing the stomach. As soon
as the incision was enlarged, the stomach presented itself at it,
and made an effort to come out of the abdomen; but I prevented it
with my hand. The nauseas returned in a few minutes, and I was
not a little surprized to see the stomach filled with air, as
they came on. In a very little time the organ had become three
times its former size; vomiting soon followed this dilatation,
and it was evident to all who were present, that the stomach had
been compressed without having experienced the least contraction
in its fibres. This organ rid itself of air and of a portion of
aliments; but, immediately after the exit of these substances, it
was flaccid, and it was not till after some minutes, that gradually
contracting, it became nearly of the same dimensions as it was
before the vomiting. A third vomiting took place, and we saw again
the same series of phenomena.

For the purpose of ascertaining whence the air came, which, during
the nauseas, distended the stomach, I applied a ligature on the
stomach near the pylorus, so as to close the communication which
exists between this organ and the small intestines, and I made the
dog swallow six grains more of emetic in powder. At the end of half
an hour the vomiting returned, accompanied by the same phenomena.
The distension of the stomach by air was at least as marked as
in the preceding experiment; besides there was no appearance
of contraction of the stomach, and we could not even clearly
distinguish its peristaltic motion. The animal having been killed
some moments after, in an experiment which had no relation to
vomiting, we examined the abdomen. We saw that the stomach was of
considerable size; its texture was flaccid and not all contracted;
the ligature, at the pylorus, was not displaced, and the air had
not been able to pass this way.

Having repeated this experiment and uniformly obtained the same
results, I thought it right to conclude with Chirac and Duverney,
that the mechanical pressure, exerted on the stomach by the
diaphragm and the abdominal muscles, is much concerned in the
production of vomiting; now, if it were so, by removing this
pressure from the stomach, vomiting would be prevented; experiment
confirmed this conjecture.

I injected into the vein of a dog four grains of an emetic
dissolved in two ounces of common water, (in this way vomiting is
produced quicker and more certainly;) I afterwards made an opening
in the abdomen, and when the first efforts of vomiting began, I
quickly drew out the whole of the stomach, which did not prevent
the efforts of vomiting from continuing. The animal made precisely
the same efforts as if he had vomited; but nothing came from the
stomach; this organ remained completely immoveable. I wished then
to see what would be the effect of pressure made on the stomach;
for this purpose, I placed my right hand on the anterior face of
this organ, and my left hand on the posterior face. The pressure
was hardly commenced when the efforts of vomiting, that is to
say, the contraction of the diaphragm and the abdominal muscles
powerfully recommenced. I suspended the pressure; the abdominal
muscles and diaphragm soon suspended their contractions. I renewed
the pressure; the contractions of the muscles began again; then I
suspended it; they ceased; and seven or eight times in succession.
The last time, I made a strong and continued pressure; this
produced a real vomiting. A part of the substances contained in
the stomach was thrown off. I repeated this experiment on another
dog; I observed the same facts; only I remarked moreover that the
contractions of the diaphragm and the abdominal muscles can be
produced by merely drawing by the œsophagus.

In the experiment just related, the emetic substance was introduced
into the veins, and we have already remarked, that the effects
were quicker and more certain than if the same substance had been
introduced into the stomach. This alone should make us suspect that
vomiting is not owing, as is generally believed, to the impression
of the emetic on the mucous membrane of the stomach; for, in this
case, its action ought to have been more prompt when it was placed
directly in contact with this membrane, than when it arrived at it
with the blood after having passed through the lungs and the four
cavities of the heart. For the purpose of elucidating this question
and of seeing if the contractions of the muscles were the result
of the impression produced on the stomach, or if they were excited
more directly by the emetic substance mixed with the blood, I made
the following experiment:

I opened the abdomen of a dog, and having brought the stomach out
at the opening, I tied with care the vessels that went to this
viscus, and I removed the whole of it (I ascertained in some of
the preceding experiments that a dog can live eight and forty
hours after his stomach has been removed.) I made a suture in
the abdominal parietes; then, having laid bare the crural vein,
I injected into its cavity a solution of two grains of emetic in
an ounce and a half of water. I had hardly finished the injection
when the dog began to have nausea, and he soon made all the efforts
that an animal does when he vomits. These efforts appeared to me
to be even more violent and longer continued than in ordinary
vomiting. The dog remained quiet about a quarter of an hour; I
then renewed the injection, and I forced two grains more of emetic
into the crural vein; this was followed with the same efforts of
vomiting. I repeated the experiment many times and always with
the same success; but this experiment suggested to me another,
which I performed in the following way: I took a dog of good size,
from whom I removed the stomach, as I had done in the preceding
experiment; I introduced into the abdomen a hog’s bladder, to the
neck of which I had fixed, by threads, a canula of gum elastic; I
put the end of this canula into the extremity of the œsophagus, and
I fixed it there also by threads, so that the bladder resembled
somewhat the stomach, and was, like it, in communication with the
œsophagus. I introduced into the bladder about a pint of common
water; this distended it, but did not fill it completely. A suture
was made in the wound of the abdomen, and four grains of emetic
were injected into the jugular vein. Nausea soon appeared, and
was followed with real efforts of vomiting; finally, after some
minutes, the animal vomited up abundantly the water from the
bladder.

It followed evidently from the preceding experiments, that the
abdominal muscles and the diaphragm concurred to produce vomiting;
but it remained to be ascertained, what was the part of the
diaphragm in the production of this phenomenon, and what was that
of the abdominal muscles.

If the diaphragm received only diaphragmatic nerves, it would be
easy to resist the contraction of this muscle by dividing these
nerves; but it also receives filaments from dorsal pairs, and
these filaments are sufficient to support its contractions. Yet
experiment shows us, that the diaphragmatic nerves being cut, the
contraction of the diaphragm is very evidently diminished in power,
and it may be said, without much hazard of mistake, that this
muscle loses, by this division, three quarters of its contractile
force. It was then useful to see what influence the division of
these nerves would have on the production of this phenomenon. I
made this division in the neck of a dog of three years old, and I
afterwards injected into the jugular vein three grains of emetic;
there was only a very feeble vomiting; another injection of emetic,
a quarter of an hour after, excited no vomiting. I opened the
abdomen and endeavoured to produce vomiting by compressing the
stomach. The compression, though very powerful and long continued,
excited no effort of vomiting; it did not even appear to produce
nausea. I thought that this circumstance might be owing to the
idiosyncrasy of the animal; but having many times since repeated
this experiment, I have never obtained any other result.

In order to understand what part the abdominal muscles by their
contractions take in vomiting, we ought to observe what takes
place when these muscles are unable to act. There is but one way
of coming at this, which is, to separate these muscles from their
attachments at the sides of the linea alba; this we have done on
many animals; we have detached successively the external oblique,
the internal oblique and the transversalis, leaving on the anterior
face of the abdomen only the peritoneum. When these muscles are
thus removed, we can see very distinctly through the peritoneum,
all that takes place in this cavity; we distinguish, for example,
perfectly the peristaltic motion of the stomach and the intestines;
and if the stomach contracts it will be easy to see it. The
abdominal muscles being thus detached, I injected three grains
of emetic into the jugular vein, and also immediately nausea and
vomiting took place by the contraction of the diaphragm alone. It
was curious to see, in the convulsive contraction of this muscle,
the whole intestinal mass pushed downwards, and pressing strongly
against the peritoneum, which was ruptured in some places. In this
case, the linea alba, formed by a very strong fibrous texture,
is the only part which resists the pressure of the viscera; its
existence then is indispensable to the action of vomiting; perhaps
it performs an analogous office in the ordinary state. This
experiment proves that vomiting can be produced by the efforts
of the diaphragm alone; this is also confirmed by the following
experiment:

I detached, as above, the abdominal muscles and laid bare the
peritoneum; I afterwards divided the diaphragmatic nerves, and
injected an emetic into the veins. The animal had some nausea, but
nothing more. Though I repeated many times the injection of the
emetic, I never was able to produce any sensible effort of vomiting.

From the different experiments that we have just related, and from
the facts that we made known in a preceding note relative to the
motions of the œsophagus, we may conclude, without any hazard,

1st. That vomiting can take place without any contraction of the
stomach.

2d. That the pressure exerted immediately on the stomach by the
diaphragm and abdominal muscles, appears to be sufficient to
produce vomiting, when the occlusion of the inferior part of the
œsophagus offers no obstacle to it.

3d. That the convulsive contraction of the diaphragm and abdominal
muscles, in vomiting from tartarized antimony and emetic substances
properly so called, is the result of a direct action of these
substances on the nervous system and independent of the impression
felt by the stomach.

[35] The motions of the iris cannot be attributed to an active
expansion of an erectile texture; they are owing to the
contractions of two muscular layers, one of which is radiated and
enlarges the opening of the pupil, the other is orbicular and
contracts it.

The motions of the iris, like all those which have muscular
contraction for their cause, can be excited for a considerable time
after death by the galvanic fluid. During life, the motions of the
pupil are produced in man, by the more or less vivid impression of
light on the retina. But they are beyond the influence of the will;
in birds on the contrary, they appear to be entirely subjected
to it. In these animals, we can even after death, and on an eye
entirely detached from the body, produce the motions of the iris by
pricking the optic nerve.

[36] When a patient dies after having for a long time been
deprived of solid and liquid nourishment, it is not rare to find
in him the stomach and intestines considerably lessened in their
two dimensions, the internal cavity almost entirely effaced, the
length being hardly a third of what it was before the disease.
We truly say then with Bichat that is a contraction from a want
of extension. But that this mode of contractility is as he says
perfectly independent of life and owing only to the arrangement
of parts, is what cannot be admitted. If it were so in fact, by
emptying the stomach after death, we might produce a contraction
similar to that which is produced during life. Now experiment shows
us, that this does not take place. The stomach when emptied remains
flaccid, and does not contract in any perceptible degree.

[37] We know that the organs are nourished, that the glands
secrete, we know that certain vessels absorb (whether they be
the lymphatics or not,) but we do not know, that all this is
produced by a _partial oscillatory movement in each fibre, in each
molecule_. No one can be certain that this movement takes place,
because no one has seen it.

[38] Why invent a new word, when we have that of elasticity,
which expresses for all bodies whether organic or inorganic, that
tendency to resume their usual form and size, when the cause that
made them change them is no longer in exercise?

[39] Bichat here unites three sorts of motion which have no
relation between them; the systole of the cavities of the heart
should be considered as a really active dilatation. The increase of
size of the corpora cavernosa, which is an effect purely passive of
the accumulation of blood in those parts, and which can be produced
after death by artificially accelerating the circulation in them;
and finally, the motion of the iris, a motion evidently produced
by a muscular contraction, excitable by galvanism or pricking the
nerve.

[40] Without denying the influence which the capillary systems of
the different organs have on the circulation, we have shown that
even in the veins the action of the heart is felt and modifies the
course of the blood.