CHAPTER XII.

OF THE INFLUENCE OF THE DEATH OF THE BRAIN OVER THAT OF ALL THE ORGANS.

When the brain dies, the animal life dies, for the functions of this life, either directly or indirectly, have their seat in the brain. It is manifest, that all the operations and affections of the mind, together with sensation, locomotion, and the voice, must be put an end to in such case. The difficulty then respects the functions of the organic life.

I. _Is the interruption of the functions of the organic life a direct consequence of the cessation of the cerebral actions?_

We shall here adduce both observation and experiment to prove, that the internal functions are all of them, as well as the action of the heart, withdrawn from the immediate influence of the brain.

1st, There are a number of diseases affecting the brain, which occasion so general a suspension of the animal life, as to leave neither sensation nor voluntary motion, excepting some feeble oscillations of the intercostals and the diaphragm. In this state the individual has lost the half of his existence, but the one half composed of the organic functions, continues in the meanwhile to subsist, and in many cases with energy. This phenomenon is exemplified continually in apoplexy, in concussion of the brain, and extravasation of blood upon its surface.

2dly, During sleep the secretions certainly go on, though Bordeu insists upon the contrary opinion, with the view of proving the influence of the nerves over the glands. During a state of sleep, digestion goes on as usually it does. The exhalations of the body are made with perfect freedom, and often augmented beyond their natural quantity; the process of nutrition continues to be effected, and is probably under such circumstances, increased. There are many proofs in favor of this opinion; but a state of sleep is a state of collapse in the brain. Then, neither is the relaxation of the functions of the internal organs the consequence of a relaxation of action in the brain, nor the death of the former the immediate effect of the death of the latter.

3dly, The sleep of animals, which pass a certain part of the year in a state of torpor, is a very strong proof of the co-existence of a suspension of the cerebral functions, with a permanent action of those of the organic life.[118]

4thly, In the different palsies; in those for instance which affect the lower limbs, and the viscera of the pelvis, in consequence of some concussion or compression of the medulla spinalis, the communication of the paralyzed parts with the brain, is either entirely cut off, or only enfeebled. It is entirely interrupted when all feeling and power of moving have ceased--it is enfeebled, when the one and the other of these properties are only enfeebled. But in these two cases the general and the capillary circulations continue. The exhalations from the cutaneous surface and in the cellular substance, are made as usual; the process of absorption goes on, for without absorption, we should soon see dropsy. The secretions also are effected, for nothing in such sort of palsy is more common than a copious secretion of mucus from the bladder. As for nutrition if it be diminished in energy, the process is certainly never entirely arrested.

5thly, Spasms and convulsions, which proceed from an unnatural energy of the cerebral action, have little influence over the exhalation, secretion, and nutrition of the parts in which they make their appearance. The trouble and excessive agitation of the animal life of such parts, compared with the calm of their organic life, are facts well worthy of remark.

6thly, Fœtuses without heads, in the uterus, possess as active an organic life, as those which have no defect of conformation whatever, and sometimes at the time of birth, are monstrous even in bulk; this circumstance I have frequently had occasion to observe at my amphitheatre; the functions of nutrition then and circulation may take place with activity, though deprived of the influence of the brain:

7thly, In animals, which have no cerebral mass, and in those (the polypes for instance) where not even a nervous system is apparent, these organic processes are admirably well conducted,[119] the greater part of them indeed are common to the vegetable, and the animal.

8thly, If the different proofs, which Bordeu has given of the influence of the brain over the functions be well examined, it will seem that no one of them is decisive. The sudden interruption of the secreted fluid, in consequence of the division of the nerves of the part, would be the only proof which I should be inclined to admit as positive. Now I am not acquainted with any means of making such division with exactness. We have heard much of an experiment of this nature upon the parotids; but the disposition of the nerves distributed to these glands is such, that I have not been even tempted to repeat the experiment. The testicle is better adapted for the attempt, and accordingly without touching the vessels, I divided the spermatic nerves, but an inflammation and a deposit of matter took place in the gland, and with respect to the secretion of the semen, I could not judge of the effect of the division of the nerves. But here this very inflammation coming on without the influence of the brain, appears to me to infer a possibility of the seminal secretion under the same circumstances. In this experiment, the spermatic artery cannot be separated from the plexus which it receives from the great sympathetic, so intricate is the network of these nerves about it; their division however is of little consequence, as they come from the ganglions. It is easy to break off all communication with the brain, by destroying the lumbar fillets of nerves.

I might add a number of other considerations to the above, but here I have to remark that the distinction of the sensibility and contractility into their two kinds is particularly worth attention. In fact, the idea of sensibility in our usual way of seeing things, suggests the idea of the nerves, the nerves again make us think upon the brain, we associate the three ideas, but excepting for the animal life they should not be associated. In the organic life, at least their union is not immediate.

I do not mean to say that the cerebral nerves have no influence whatever over the organic sensibility, but I maintain that such influence is not direct and not of the nature of that which is observed in the animal sensibility.

Many authors have already discovered a number of difficulties resulting from the opinion which makes the nerves the exclusive seat of sensibility, they have even sought for other means of explaining the phenomena of great living bodies. But of its agents we know as little as we do of its nature, and have no means of elucidating questions of this sort. Let us be contented with analyzing, collecting and comparing facts with seizing their general results; the aggregate of these researches will compose the true theory of the vital powers; the rest is only conjecture: but besides the considerations which I have offered, there is another which manifestly goes to prove that the organic functions are not under the immediate influence of the brain, and this is, that the viscera, which perform such functions do not receive their nerves from the brain but from the ganglions.

This anatomical fact is observable in the liver, the kidney, the spleen, pancreas, intestines, &c. even in the organs of the animal life there are nerves which serve for the external, and nerves which serve for the internal functions. In such the former come directly from the brain, the latter from the ganglions. Thus the ciliary nerves, which come off from the opthalmic ganglion, are those which preside over the secretions and nutrition of the eyes, the optic nerve which is derived from the brain is the nerve of vision.[120] In the same way the olfactory nerves of the pituitary membrane are the agents by which we have the perception of odours, the threads which come off from the ganglions of Mekel, relate only to the organic phenomena of the membranes.

Now the nerves of the ganglions cannot transmit the action of the brain; for we have seen that the nervous system derived from these bodies should be considered as entirely independent of the nervous system of the brain; and that the great sympathetic does not derive its origin from the brain, from the spinal marrow, or from the nerves of the animal life; but from the ganglions exclusively; this nerve indeed does not exist, it is only the aggregate of so many small nervous systems as there are ganglions, which are the particular centres of the organic life, just in the same way as the brain is the great and only centre of the animal life.

To establish it as a fact that the great sympathetic such as it is understood does not in reality exist, I might add a number of proofs to those, which I have already mentioned. The nervous communications, which are taken for it, are nothing more than accessories to the system of the ganglions; for 1st, These nervous communications, as Cuvier has observed, are not met with in the necks of birds; between the upper cervical and first thoracic ganglion there is no vestige of a sympathetic. In birds then, the upper cervical ganglion is that which in man the opthalmic ganglion, the ganglion of Mekel and others are. This disposition, which is natural in birds, agrees with what I have sometimes observed in the human subject between the first lumbar and the last thoracic ganglions, as well as between the lumbar and sacral ganglions themselves. 2dly, In many instances there are no ganglions in the spot where the pretended sympathetic nerve communicates with the spinal marrow. This may be seen in the human neck, and in the abdomen of fish, but such disposition should be thus regarded. The inferior cervical ganglion furnishes a great branch which ascends to the superior cervical ganglion, and establishes between the two a direct communication; but in ascending it distributes many branches to each of the cervical nerves, which form a secondary communication.

If we reflect on these considerations, together with those which have been already offered, we shall be more and more convinced--1st, That the great sympathetic is only an assemblage of small nervous systems, having each of them a ganglion for its centre, and all of them independent of each other, though generally communicating with the spinal marrow and between themselves. 2dly, That the nerves belonging to these small systems, cannot be considered as a part of the great nervous system of the animal life. 3dly, That the organs, which are provided exclusively with the nerves, are not under the immediate influence of the brain.

Notwithstanding which, we must not suppose that all the organs which serve for the internal functions, receive their nerves exclusively from the ganglions: many of these organs are furnished from the brain, and yet from experiment, it is found that they are not under the immediate influence of the brain.

As yet we have only observation and reasoning for the basis of the important principle which we are labouring to establish, namely, that the organic functions are not directly put a stop to in consequence of the death of the brain; but experiments upon living animals are not a less evident demonstration of this principle.

1st, I have always observed, that in producing palsy or convulsion, I have never been able to impair in any very sensible or sudden manner, either the exhalation, the absorption, or the nutrition of the convulsed or palsied part.

2dly, It has been for a long time known, that no spasm of the muscular fibres of the stomach, bladder, or intestines, can be produced by irritating the nerves of the ganglions which go to these organs.

3dly, The division of the nerves of the ganglions, will not immediately paralyze the hollow organs. Their vermicular motions continue for a long time after the experiment.

4thly, With respect to the stomach, intestines, bladder and uterus, I have repeated the galvanic experiments which, with respect to the heart, have already been mentioned at length; but never could obtain contractions.[121]

5thly, The same experiments being made upon the organic muscles, and the great sympathetic nerve of a dog, there was no contraction.

6thly, The issue of the latter operation may be easily conceived, according to our manner of regarding things. In fact, the ganglions, which are situated between the gastric organs and the nervous trunk of the chest, might possibly have interrupted the series of the galvanic phenomena. With a view, then, to remove all doubt of this kind, I exposed the nerves, which go from the ganglions immediately to the stomach, bladder and rectum, and in this way galvanised the organs but no contraction appeared to me to be the result of the experiment; at least no contraction, which I could suppose to be the effect of galvanism, for here I cannot too much recommend a proper distinction to be made between that which should be the effect of this fluid, and that which results from the mechanical contact of the metals.

7thly, These experiments are not easily made upon the intestines, on account of the tenuity of their nerves; but as these nerves compose a very perceptible plexus about the mesenteric artery, the intestine may be galvanized by surrounding the artery with one of the metals, while the other is placed under the intestinal tube. This experiment I have made, but could not obtain any sensible result.

8thly, The preceding essays were made upon warm and red-blooded animals. Similar attempts were repeated on cold and red-blooded animals, but with no effect.

9thly, The nerves which immediately supply the gastric organs of the frog, are so delicate as to make it an extremely difficult matter to get them into proper contact with the zinc: a small contraction of the stomach was, however, obtained by Jadelot on operating directly on these nerves; but this contraction was similar, no doubt, to those which I have so frequently observed in other experiments, and not to be compared to the astonishing effects which are observable in the voluntary muscles. I shall conclude, therefore, that with respect to the galvanic phenomena, there exists a wide difference between the muscles of the animal life and those of the organic life.

I have now collected proof enough, I trust, for resolving, with certainty, the question proposed in the above chapter, and for establishing it as a fundamental principle.--1st, That the brain does not directly influence the organs and the functions of the internal life; and 2dly, That, therefore, the interruption of these functions, in case of any great lesion of the brain, is not an immediate effect of such lesion.

Nevertheless, I am far from considering the cerebral action as foreign entirely to the organic life. I only maintain that its influence upon it is indirect, and as yet but little known. I have been somewhat prolix upon this subject; for certainly nothing in medicine is more vague than the sense which is commonly attached to the words _nervous action_, _cerebral action_, &c. There is never a proper distinction made between that which belongs to one life, and that which is the attribute of the other. Cullen, in particular, may be reproached with having exaggerated the influence of the brain.

II. _Is the interruption of the functions of the organic life, the indirect effect of the cessation of the cerebral action?_

The organic life continues to subsist for a certain time, after the apparent death of the individual. There must be some intermediate agents then, the cessation of the action of which, occasions the death of the inward organs. Such agents are chiefly the mechanical organs of respiration. The series of the phenomena are the following:

1st, The cerebral actions are interrupted.--2dly, The mechanical functions of the lungs are put an end to.--3dly, There is an annihilation of their chemical functions.--4thly, The black blood circulates in all the parts.--5thly, The movement of the heart and the action of all the parts is weakened.--6thly, Suspended.

All the inward organs then, die nearly as they do in asphyxia; that is to say--1st, Because they are penetrated by the black blood.--2dly, Because the circulation ceases to communicate that motion which is essential to their life.

Nevertheless, there are many differences between death from asphyxia, and death from lesion of the brain. 1st, The animal life in the latter sort of death, is generally interrupted at the very instant of the shock or blow. In the former it is terminated only in proportion as the black blood penetrates the substance of the brain.--2dly, In the greater number of the asphyxiæ, the circulation does not immediately cease, the blood is only gradually blackened, and continues for some time to be moved onwards by the agitation of such parts as are still under the influence of the brain. On the contrary, in lesion of the brain, the interruption of respiration is sudden; the blood also loses its red colour at once: on the other hand, the animal life being suddenly arrested, the organs of volition become immovable on the spot, and are capable no longer of favouring the motion of the blood. This remark is particularly applicable to the breast, the parietes of which facilitate very much the pulmonary circulation, and even the movements of the heart by their rise and fall, for in such alternation of motion consists the true influence which the circulation receives from the respiratory process.

But after all, these two sorts of death may be more or less similar to each other according to the way in which they happen. The differences which I have pointed out are by no means general. Thus, when asphyxia is sudden, as when for instance the air of the lungs is pumped out with a syringe, there are neither livid spots, or fulness of the lungs to be met with. The circulation ceases quickly, and the phenomena of death are such as are observable when the brain is suddenly destroyed.

On the contrary, if the death of the brain be slow, and the process of respiration for a certain time continued, the capillary system of the lungs will be gorged with blood, and the general capillary system be filled also. The circulation in such case will be slow to cease, and the phenomena of death like those of many of the asphyxiæ. Thus the promptitude or slowness of death, proceeding from lesion of the brain, will occasion all the differences.

It has been often a question in what way criminals die, who are hanged. In some, the vertebral column is luxated, and in others, want of respiration is the cause of death.[122] But whenever there is luxation, there is at the same time asphyxia, and in such case asphyxia is produced, both because the pressure of the cord intercepts the passage of the air, and because the intercostals and diaphragm are paralyzed.

From what I have now said, a comparison may be made between the three kinds of death upon which I have expatiated. This comparison, according to my ideas, is of importance: I shall give some features of it. Generally speaking, there is a greater similarity in the two modes by which the death of the brain, or that of the lungs produces the death of the organs, than between either of these modes, and that, where the death of the heart is followed by the same effect.

But 1st, There is always black blood in the red-blooded system, when death begins either by the brain or the lungs. When the functions of the heart are suddenly suspended, the arterial system contains a portion of red blood only.

2dly, In the two first cases, the circulation continues for awhile; in the third, it is immediately suppressed.

3dly, When the death of the organs is a consequence of the death of the heart, they die, because they cease to receive that excitement, to which they are accustomed from the motion of the blood. When their death is produced by that of the brain or lungs, they die not only because they lose the excitement above-mentioned, but because they are penetrated by a fluid which is incapable of keeping up their actions, &c. The reader will easily finish the parallel which I have thus begun.

In red and cold-blooded animals, the death of the organs succeeds much more slowly to that of the brain, than in red and warm-blooded animals. We cannot assign the reason of this fact, because we do not know the difference of the arterial blood from the venous blood of these animals, nor the effect which is produced on their organs by the contact of either sort of blood with them.

When reptiles remain for a length of time under water, does the arterial blood become black from want of respiration? is the influx of such blood into their organs, pernicious or not?[123] or is there a sufficient quantity of air contained in the large vesicles of the lungs of these animals to oxydate their blood for a length of time, as but little blood is capable of passing into the pulmonary artery, which is only a branch of the aorta. The latter opinion appears to be confirmed by the experiment of injecting the lungs of a dog with a large quantity of air, in which case the blood of the creature is reddened for a greater length of time. But all these questions, notwithstanding the essays of Goodwyn, require much elucidation.

FOOTNOTES:

[118] When two states, which are not perfectly similar, are designated by a common name, it is very difficult, whatever care may be taken to distinguish them, not to apply to one something which exclusively belongs to the other. This is perhaps one of the most frequent sources of our errours. In this case, for example, it does not seem that there is a great inconvenience in designating by the word sleep the state of torpor of certain animals during a part of the year. It is well known that we understand by it altogether a different thing from the sleep, which in warmer seasons of the year, comes on periodically every day; yet in consequence of the identity of the name, we are disposed to admit identity of character and to infer from one respecting the other.

[119] What is the circulation of an animal which exhibits no trace of vessels? what inferences can be drawn for man from the mode of nutrition of a polypus? what relation can be established between the complex function which presides in the mammalia over the support of the organs, and the kind of imbibition by means of which the zoophyte is developed and preserved?

[120] The external ciliary nerves only come from a ganglion. The internal ciliary ones which have precisely the same distribution and serve also very probably the same uses, come from a cerebral nerve, from the nasal branch of the ophthalmic.

[121] The galvanic stimulus usually produces very evident effects upon the contraction of the intestinal tube; these motions are less evident in the stomach than in any other part of the canal; but the same difference is always observed whatever be the stimulus employed.

[122] Death does not always take place in the same way. It has been remarked, for example, that those who were hung at Lyons died quicker than those who were hung at Paris. In seeking for the cause of this difference, it was ascertained that in those who were executed at Lyons there was almost always a luxation of the first or the second vertebra, which was owing to a rotatory motion, which the executioner gave to the criminal in throwing him from the scaffold. The death was quick, because it was produced by compression or laceration of the spinal marrow; it was slower in the other case in which it was only the result of asphyxia.

[123] It appears by the beautiful experiments of M. Edwards that frogs can live but a very short time in water deprived of air by boiling. Immersed in a small body of water containing air they soon die, no doubt after they have exhausted the air held in solution in the water. They can on the contrary live an indefinite time in this state of immersion, if care be taken to renew the water sufficiently often. The same thing happens, and still more certainly, if they are immersed in running water.

It is not by passing the water through the lungs, as the fish does through the branchiæ, that the frog obtains the air held in solution by the water in which he is immersed, the skin is in this case the sole respiratory organ. M. Edwards is satisfied that this mode of respiration is not sufficient to support life, except between certain limits of temperature; a frog immersed in a volume of water which is not changed, continues to live so much the longer as the temperature of this fluid approaches nearer 32°. At this degree frogs are not torpid, as might be supposed, only their motions are slower.

As long as the animal immersed in the water remains perfectly alive, which may be known by the vivacity of his motions, it is certain that the respiratory phenomena continue to be performed by him; we see in fact on the membranes in the interstices of the toes, the vessels filled with vermilion blood. When the black colour begins to appear, the animal soon becomes immoveable and insensible.