CHAPTER XI.

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.