OF THE INFLUENCE OF THE DEATH OF THE BRAIN OVER THAT OF THE HEART.
In the preceding chapter we have shewn how the lungs remain
inactive, when the brain ceases to act.--The same phenomenon, under
the same circumstances, takes place also in the heart, and must
happen either immediately or mediately.
I. _Does the Heart cease to act immediately in consequence of the
interruption of the cerebral action?_
The greater number of medical men, speak in much too vague a manner
of the cerebral influence. They do not sufficiently determine its
extent and limits, with respect to the different organs of the
system.
It is evident that we shall have answered the question proposed at
the head of this section, if we can determine what the influence of
the brain is with regard to the heart. Now, we have every reason to
suppose, that no direct influence is exercised by the former over
the latter of these organs, which, on the contrary, is immediately
dependent with regard to its operations, on the movement
communicated to it by the blood. This assertion is by no means a
new one. It has been admitted by all sound physiologists; but as
many opinions in medicine are founded upon a contrary principle,
it will not be amiss to dwell upon it a little. It is equally
demonstrated both by observation and experiment--and to begin with
the former:
1st, All violent irritation made upon the brain, produces either
partial, or general convulsion in the muscles of the animal life.
Examine those of the organic life, on the contrary, and little will
be found amiss in their actions.
2dly, All compression of the cerebral mass, whether made by pus,
water or blood, has ordinarily the effect of paralyzing the
voluntary muscles; but so long as the affection does not extend to
the muscles of the breast, the action of the heart is in no degree
diminished.
3dly, Opium and wine, when taken in a certain quantity, diminish
the cerebral energy for the moment and render the brain unfit for
the functions of the animal life. The action of the heart, on the
contrary, is increased.
4thly, In palpitation, and the different irregular movements
of the heart, it is not observable that the principle of these
derangements exists in the brain.--In this respect, as well as on
the subject of syncope, Cullen has been mistaken. The brain during
such time, continues in action as usual.
5thly, The numerous phenomena of apoplexy, and epilepsy, and
concussion, &c. do certainly all of them tend to shew, how
independent the heart is of the brain.
6thly, Every organ which is subject to the direct influence of the
brain, is for that very reason an organ of volition. Now, I should
suppose, that few persons of the present day, would be inclined to
maintain with Stahl, that the heart is among the number of such
organs. What would life be, were we able at will, to suspend the
action of the organ, by which the system is animated? From simple
observation, then, we might conclude, that it is not immediately
that the heart ceases to act, when the functions of the brain
are interrupted, but this fundamental datum of physiology and
pathology, we shall further establish, upon actual experiment.
1st, If the brain of an animal be exposed, and irritated either
with mechanical or chemical agents, a variety of alterations will,
indeed, be produced in the organs of the animal life, but none in
the heart, so long as the muscles of the breast continue to perform
their functions.
2dly, Experiments made in the same manner upon the spinal marrow of
the neck, present the same results.
3dly, If the eighth pair of nerves be irritated, the movements of
the heart will not be accelerated; they will not be arrested if
these two nerves be divided. In all these experiments, however, we
must be careful to make a proper distinction between the emotions
and passions of the animal, and what it really suffers from the
experiment.
4thly, The nature of the great sympathetic nerve, I suppose to be
known;[114] now if the same experiments be made on the cardiac
branches of this nerve, as were made upon the eighth pair, the same
results will follow.
I do not offer in detail the whole of these experiments; the
greater part of them are well known: I was induced to repeat them,
as authors are not agreed upon their consequences.
The experiments of galvanism, are well calculated to throw light
upon the relations existing between the heart and the brain; these
I have taken care to repeat with the utmost exactness, and whatever
authors may have advanced, they are all in favour of the above
opinions--for 1st, If the galvanic apparatus be applied to the
brain, and to the heart, and inferior extremities of a frog, and
the communication made between the metals, there will constantly be
seen a strong contraction in the muscles of the limb, and little or
none in the heart. The same will be the case, to whatever voluntary
muscle the zinc be applied. 2dly, The same results will be had, on
the communication being made between the metals applied on the one
hand to the spinal marrow above the giving off of the sympathetic,
and on the other hand to the heart, and any of the voluntary
muscles.
3dly, On establishing a communication between the metals applied
to the cardiac nerves, and to the heart of the animal, there
has been no contraction in the heart. In all these essays, the
natural disposition between the parts which serve to unite the two
organs, is preserved: there are other experiments which consist in
detaching the heart from the breast. 2dly, In placing two points of
its surface in contact with two different metals. 3dly, In making
the communication between them with a third. From this experiment,
Humboldt and other philosophers have procured contractions, but I
have taken care to repeat it with the greatest accuracy, and must
assert, that I have seen little or nothing of the kind; indeed, if
I had, I should have concluded nothing from it; for it appears to
me, that to decide upon the influence of the brain over the heart,
a portion at least of the nervous system, should be in contact with
one of the metals.
I shall now pass to my experiments on red and warm-blooded animals.
They are necessary for the decision of the question before us, as
the mode of contractility in these animals differs much from that
of the animals submitted to the experiments already mentioned.
1st, In the winter of the year 1798, I was authorized to make
different essays on the bodies of persons who had been guillotined.
I had them at my disposal thirty or forty minutes after they
had undergone the punishment. In some of them, all mobility was
extinct; in others, this property could be reanimated in all the
muscles by the common agents, and in those of the animal life, by
galvanism especially.[115] Notwithstanding which, I could never
occasion the least motion, in applying the apparatus either
to the spinal marrow and the heart, or to this latter organ
and the nerves, which it receives from the ganglions of the
sympathetic, or the par vagum. Nevertheless, the common mechanical
excitant, immediately applied to the fleshy fibre, occasioned
its contraction. Could this have happened in consequence of the
separation of the nervous fillets from the brain? assuredly not;
because the voluntary muscles were equally separated from it,
and yet affected strongly. If any doubt remain, the following
experiments will clear it up.
2dly, In dogs and guinea pigs, I have repeatedly applied the
metals, first to the brain and the heart, then to the trunk of the
spinal marrow, and the heart; then to the par vagum and the heart.
The communication being made, was followed by no apparent result.
3dly, On making the communication between the metals, when applied
to the cardiac nerves and the heart, there was no very sensible
motion.
4thly, Humboldt has asserted, that when the heart is speedily
detached with some of its nervous threads about it, a contraction
may be excited, by arming the nerves with a metal, and then by
touching this metal with another. I have many times tried this
experiment in vain. I confess, however, that once it appeared to me
to succeed.
5thly, On the contrary, I have almost always succeeded in producing
contractions in the heart, by cutting it away from the breast,
and making a communication between a couple of metals, applied to
different points of its surface. This, if I am not mistaken, is
the only means of evidently producing the phenomena of galvanism
in this organ, but with respect to our present question, the
experiment is wholly inconclusive.
All these experiments I have repeated many times, and with the most
scrupulous precautions, nevertheless I do not pretend to call in
question the reality of those results, which other physicians have
remarked. It is well known how very variable those experiments
are, which have the vital powers for their object. Besides, in
admitting even these different results, I do not see how it is
possible to refuse acknowledging, that with respect to the stimulus
of galvanism, there is a wide difference between the susceptibility
of the muscles of the animal life, and those of the organic life.
Again, supposing that the galvanic phenomena were the same in
both sorts of muscles, the fact would prove nothing more, than
that these phenomena with regard to their succession, follow
laws directly the contrary of those, which are displayed in the
phenomena which take place, when any common cause of irritation is
applied to the nerves and their corresponding muscles.
The proofs adduced, will allow us to conclude, that the brain
exercises no direct influence over the heart, and consequently,
that when it ceases to act, the functions of the latter must be
interrupted indirectly.
II. _In case of lesion of the brain, is the death of the heart
occasioned by that of any intermediate organ?_
When the brain dies, the heart dies, but not directly. There must
be some intermediate organ then, the death of which occasions that
of the heart.[116] That intermediate organ is the lungs. In this
sort of death, the following is the series of the phenomena which
may be observed.
1st, The cerebral action is interrupted. 2dly, The action of
all the muscles of the animal life, and consequently of the
intercostals and diaphragm, is annihilated. 3dly, The mechanical
functions of the lungs are suspended. 4thly, The like ensues with
respect to their chemical functions. 5thly, The fibres of the
heart are penetrated with black blood. 6thly, The fibres when so
penetrated, die.
Such sort of death then, has much resemblance with that which is
occasioned by the different asphyxiæ. It is only more sudden, and
that for reasons which I shall presently point out. The following
experiments are an evident proof that the phenomena take place as
I have described them to do.
1st, I have always found black blood in the red-blooded system of
all animals, killed by concussion or compression of the brain; the
heart livid, and the different surfaces coloured as in asphyxia.
2dly, I opened the carotid artery of a dog; the red blood instantly
gushed out, but was immediately suppressed, and the artery tied.
I then killed the creature, by striking him with violence on the
occipital bone.[117] The animal life, and consequently both the
mechanical and chemical functions of the lungs, were suddenly
suppressed. The artery was then united. It poured forth the black
blood with a feeble jet, for some little time, and after some
minutes, the heart entirely ceased to move.
3dly, I have always obtained a similar result in opening the
arteries of different animals which I afterwards killed, either by
dividing the marrow between the first vertebra and occiput, or by
strongly compressing the brain, which I had previously exposed.--It
is thus also that animals perish, by the carotids of which a
deleterious substance has been injected.
4thly, The preceding experiments explain the reason why the blood
is black which flows from the arteries of animals, which are bled
in our slaughter-houses, after having been knocked in the head.
If the blow has been violent, the blood issues such as it was in
the veins, but if the action of the diaphragm and intercostals has
only been weakened by the blow, the redness of the blood is only
diminished.
The state in which the respiration may be (and it is altered from
a variety of circumstances during profuse hemorrhagy) occasions a
great variety in the colour of the arterial blood: hence we have
the reason why it is found of so many different shades in the great
operations of surgery. At the beginning of these, it often flows
out quite red; at the end of them, is sometimes almost black. The
easy or embarrassed state of the respiration of the patient, is the
occasion of these varieties. This I have frequently remarked, when
attending Desault, and was often struck with the appearance, before
I knew the cause of it.
I have never found any relation whatever, between the obscure
colour of the blood, and the compression exercised above the
artery, as some have asserted to take place. There is, indeed, a
connection between the colour and the impetuosity of the jet, but
the reason of this is evident to any one who has read the foregoing
pages.
To return to the point of doctrine on which we are at present
occupied, I am persuaded from the considerations and experiments
which are adduced in the course of this chapter, that the manner
in which the heart ceases to act, when the cerebral functions are
suspended, can no longer admit of a doubt, and that we may resolve
the question proposed, in affirming that under such circumstances,
the death of the heart is occasioned through the medium of that of
the lungs.
There is this difference, then, between the death of the heart,
in consequence of that of the brain, and the death of the brain
in consequence of that of the heart, that the one is indirect,
the other direct, as we have already seen. If some men, as Stahl
asserts, have really been able to suspend the movements of the
heart, the fact is not a proof of the influence of the mind over
the muscles of the organic life, but of its power over the
mechanical, and consequently, the chemical phenomena of respiration.
In red and cold-blooded animals, the death of the heart does not
succeed the death of the brain so quickly as it does in red and
warm-blooded animals. Cut off the head of a frog, and the heart
will continue to beat for some time afterwards. This phenomenon
will be easily accounted for, if we recollect that respiration with
these animals may be suspended a length of time, without arresting
the movements of the heart.
In fact, as the heart dies only because the lungs die in the
first place, when the cerebral functions are interrupted, it is
plain that there ought to exist between the violent death of the
heart and that of the brain, an interval nearly equal to that
during which, in the natural state, there may be a suspension of
respiration.
FOOTNOTES:
[114] Physiologists have paid much attention to the great
sympathetic nerve. They have made, in relation to its uses, many
conjectures but few experiments; so that we have not on this
subject any very precise notions. The deep situation of the
ganglions renders them almost inaccessible, the superior cervical
is almost the only one that can be taken out without producing
death. M. Dupuy, Professor of the Veterinary School at Alfort, has
discovered a method by which he can remove them with ease. We shall
now relate some of his observations.
“_1st Experiment._ The first experiment was made on a young and
vigorous horse, who had been treated for the glanders; it soon
appeared that he was not affected with it, and that it was merely
the caries of a tooth that had led to the belief of the existence
of the disease.
“On the 24th of June his left guttural ganglion was extirpated.
Soon after the operation, the eye of that side appeared to be
more sunk in its socket, the eyelids were swelled and the pupil
contracted.
“On the 28th of June the sub lingual ganglion appeared swollen,
hard and attached; a discharge of fetid, greyish matter was
discovered in the nostril of the same side.
“On the 29th of June, the wound suppurated copiously.
“From the 30th of June till the 16th of July the wound advanced
rapidly towards cicatrization.
“From the 18th of July to the 15th of August the animal continued
in the same state of health.
“On the 15th of August, the right guttural ganglion with a portion
of the nerve was removed; this operation was followed by the
same phenomena as the preceding, with this difference, that two
days after the animal could not swallow water, it run out at the
nostrils. There was in fact a communication between the nostrils
and mouth from the caries of the back molar tooth, the roots of
which were opposite the maxillary sinus, that had an opening into
the nostril; the voice was lost.
“On the 20th of August, he was much emaciated, with the skin dry
and adherent; the cheeks, below the jaw, were constantly moistened
with sweat, which had been observed for twelve or fifteen days. The
wound of the right side remained fistulous; the skin was covered
with scurf, the sheath and scrotum, as well as the hind legs, were
oedematous; the animal died. Nothing remarkable was discovered on
dissection. Below the sub-occipital foramen the great sympathetic
was slightly swelled, in the form of a knot, in the place where the
division had been made.”
“_2d Experiment._ On the 26th of April, the right guttural
ganglion, with a portion of the nerve, was removed from a sound
horse, four and a half years old, strong and in good condition.
The ganglion of the left side was first a little mutilated, and
the nerve was removed posteriorly to the extent of thirty three
centimetres. The animal did not manifest so much pain as might have
been expected.
“The conjunctiva soon became red and the eyelids partly covered the
eyes; the respiration became painful and loud; the pulse was hard,
strong and frequent. The animal refused all food, and drank with
great difficulty.
“This state continued till the 10th of May following. The two
wounds were almost healed; the animal eat and drank well; but the
hind legs and scrotum were still so much swollen as to interfere
with his walking; the conjunctiva remained red and the pupil
contracted.
“Towards the 13th of May the skin became adherent and covered with
scurf; the cutaneous respiration was nearly destroyed.
“On the 25th of May, the swelling of the legs and the scrotum
became considerable, notwithstanding the frictions with water and
turpentine, which were made several times a day since the 13th; he
could, with difficulty be got out of the stable to be examined. The
pulse retained its hardness and frequency. The dung was hard, black
and small.
“During the month of June the phenomena were similar to those we
have enumerated; the swelling of the scrotum and the legs resisted
the tonic and stimulating applications.
“On examining the body, the ends of the nerves that had been drawn
out were found swollen as in the first horse. Similar results have
been obtained in all the other experiments that have been made on
this subject. It may be said in conclusion, that the phenomena
which appear after the removal of this ganglion, and which do
not depend on the operation, are the contraction of the pupil,
the redness of the conjunctiva, general emaciation, accompanied
with swelling of the legs, and a scurfy eruption which ultimately
affects the whole cutaneous surface.”
[115] Galvanic experiments have at different times been made on the
bodies of those who have been executed. Vassali, Julio and Rossi
made a great number of them at Turin; but the piles that were then
used were very weak compared with those that are now employed. In
the experiments made at Newgate on the body of a criminal, the
limbs were violently agitated, the eyes opened and shut, the mouth
and the jaws moved in every direction, and the face was thrown
into the most frightful convulsions. The last and most complete
experiments, that we know of, were made at Glasgow in November 1818
by Dr. Andrew Ure. He used for these experiments a battery composed
of two hundred and seventy pair of plates four inches square, with
communicating wires, and so arranged that they could be insulated
for the purpose of applying the electricity in a more convenient
manner.
The subject, on whom these experiments were made, was of middle
height, about thirty years of age and of an athletic constitution.
He was on the gallows almost an hour, and he was not convulsed
after being hung, whilst a robber executed at the same time was
violently agitated for a considerable time. He was carried to the
anatomical theatre of the university, about ten minutes after he
was removed from the gallows. His face had a perfectly natural
appearance being neither livid nor swollen, and the neck was not
dislocated.
About five minutes before the arrival of the police officers with
the body, the battery was charged with diluted nitro-sulphuric
acid, which quickly put it in a state to exert an intense action.
_1st Experiment._ A large incision was made immediately below the
occiput. The posterior half of the first vertebra was then removed
and the spinal marrow laid bare, at the same time a considerable
incision was made in the great glutæus muscle, in order to expose
the sciatic nerve. A slight incision was made in the heel; no blood
escaped from any part. A wire which communicated with one extremity
of the battery was put in contact with the spinal marrow, whilst
the other was applied to the sciatic nerve. All the muscles of the
body were in an instant agitated with convulsive motions which
resembled a violent shuddering. The strongest convulsions were on
the left side; at each time of renewing the electric contact by
moving the second wire from the haunch to the heel the knee being
previously bent, the leg was thrown out with so much force, that it
threw down one of the assistants who in vain endeavoured to prevent
the extension.
_2d Experiment._ The left phrenic nerve was laid bare towards the
external edge of the sterno-thyroideus muscle, three or four inches
above the clavicle; as this nerve goes to the diaphragm, and as it
communicates with the heart by the eighth pair, it was expected,
that by throwing the galvanic fluid through it, the action of
respiration would be renewed. In consequence a small incision
having been made under the cartilage of the seventh rib, the point
of an insulated wire was placed in contact with the diaphragm,
whilst the other was applied to the phrenic nerve of the neck. This
muscle, the principal agent of respiration, contracted immediately,
but with less force than was expected. As I knew by numerous
experiments that we could produce the most powerful effects from
the galvanic fluid, by leaving the extreme communicating wires
perfectly in contact with the parts on which we wished to operate,
whilst, in order to complete the electric chain, we carried the
end of the wires the length of the plates, into the last trough
of one of the poles and immediately plunged the other wire into
the last cell of the opposite side, I had recourse to this measure
without loss of time. The success was truly astonishing; instantly
commenced a strong and laborious respiration. The chest rose and
fell; the abdomen was pushed forward and then flattened, and the
diaphragm contracted and relaxed. All these motions appeared
without interruption as long as I continued the electric excitement.
In the opinion of many scientific persons who were witnesses of
this scene, this experiment was perhaps the most striking that
had ever been made with an electrical apparatus. It should be
recollected that during half an hour at least, before this, the
body had been nearly exhausted of blood and the spinal marrow had
been much lacerated.
No pulsation could be perceived either in the heart or at the wrist.
_3d Experiment._ The suborbitar nerve was laid bare at its
exit from the suborbitar foramen. One of the conducting wires
was applied to the nerve and the other to the heel; the most
extraordinary grimaces were produced. All the muscles were put
simultaneously in action in a frightful manner; rage, horrour,
despair, anguish and frightful smiles united their hideous
expression in the face of the assassin. At the sight of this, many
of the spectators were obliged to leave the room and one of them
fainted.
_4th Experiment._ The last galvanic experiment was made by
transmitting the electric fluid from the spinal marrow to the
cubital nerve near the elbow; the fingers moved quickly like those
of a performer on a violin; one of the assistants who endeavoured
to keep the hand shut, found that it opened in spite of his
efforts. A wire was applied to a slight incision made at the end of
the first finger; the hand had been previously shut; the finger was
instantly extended, and, after a convulsive agitation of the arm,
the dead man seemed to point his finger at the spectators, some of
whom thought that he had come to life.
An hour was consumed in these experiments.
[116] It is shewn by the beautiful experiments of M. Legallois,
that the heart derives the principle of its forces from the spinal
marrow, and from the whole spinal marrow, since the destruction of
one of its three portions can arrest completely the circulation.
The destruction of the spinal marrow does not entirely annihilate
the motions of the heart; but it weakens them sufficiently to
prevent the circulation, and this weakening is so much the greater,
as the portion of spinal marrow destroyed is larger. It may be
presumed from this, that notwithstanding the weakening which
follows the removal of a part of this marrow, the circulation
may still continue if we lessen the sum of the forces which the
heart must expend to maintain it. For this it is only necessary to
diminish by ligatures on the arteries, the extent of the circle to
which the heart distributes the blood. This conjecture is confirmed
by experiment. It has been seen, for example, that the destruction
of the marrow which is very suddenly fatal in full grown rabbits,
ceases to be so, if before doing it the abdominal aorta is tied
between the coeliac and the superior mesentric arteries. The
application of the same principle to other parts of the body leads
to a still more surprising result, it is this, that in order to
support life in rabbits of a certain age, after having destroyed
the cervical marrow, it is necessary first to cut off the head.
They will be completely dead if the marrow be destroyed before they
are decapitated; this arises from the fact, that by cutting off the
head all this part is taken out of the domain of the circulation,
and that by it the heart having need of less force to continue
its function, we can weaken it by the destruction of the cervical
marrow without its ceasing to perform it.
[117] When an animal is thus struck, it is not certain that the
concussion has not extended its effects upon a greater or less
part of the spinal marrow; and it is not known consequently if the
motions of the heart would not cease, even when asphyxia might be
prevented by means of artificial respiration.