FOOTNOTES:[48]I am persuaded that the still very obscure theory of the fœtus might be elucidated by that of animals who have a similar organization. For example, in the frog, in whom but little blood goes through the lungs, the heart is a simple organ, with a single auricle and ventricle; there is a communication or rather continuity between the two systems, venous and arterial, whilst in the mammalia, the vessels in which the red blood circulates do not communicate with those which carry the black blood, except it be by the capillaries.In the fœtus, the foramen ovale and the ductus arteriosus also render very evidently the arteries and veins continuous; in the fœtus the heart is likewise a simple organ, not forming, notwithstanding its partitions, but one cavity whilst it is double after birth. The two kinds of blood mix at this period, as in reptiles. Now, I shall prove hereafter, that in the child who has breathed, this mixture would soon be fatal; that the black blood, circulating in the arteries, would very quickly produce asphyxia in the animal. Whence arises then this difference? It cannot be studied in the fœtus; it is necessary perhaps to search for it in frogs, salamanders and other reptiles, which can, by their organization, be a long time deprived of air without dying, a phenomenon which approximates them to the mammalia while living in the womb of the mother. Till these very important researches are made, the history of respiration will be incomplete.[49]This explanation is no doubt ingenious, but it is insufficient, since the causes which Bichat assigns for the rapidity of the growth of the fœtus cease entirely at the moment of birth, and yet the growth continues for a long time after to be as rapid.[50]When two phenomena are seen to follow each other immediately, we are naturally led to consider one as the cause of the other.Post hoc ergo propter hoc.It is a form of reasoning which is very often abused. Food taken into the mouth touches the orifice of the salivary ducts, the fluid flows out, and it is then concluded that the salivary gland has been excited by the impression made on the extremity of its canal. At the moment of birth, the orifice of the urethra is exposed to the contact of the air, and soon the kidneys begin to secrete; then it is the impression of the air on the urethra that has produced their action. But is not this contact of the food in the one case, and of the air in the other an accidental and purely accessory circumstance? Do we believe, that if by any cause the opening of the prepuce was entirely obliterated, the secretion of urine would be prevented? Do we not know that if instead of taking into the mouth savoury food, it is brought near to it, the saliva flows not less, or in vulgar language the mouth waters? There is however no contact, there is not any mechanical or chemical impression in the orifice of the salivary ducts.
[48]I am persuaded that the still very obscure theory of the fœtus might be elucidated by that of animals who have a similar organization. For example, in the frog, in whom but little blood goes through the lungs, the heart is a simple organ, with a single auricle and ventricle; there is a communication or rather continuity between the two systems, venous and arterial, whilst in the mammalia, the vessels in which the red blood circulates do not communicate with those which carry the black blood, except it be by the capillaries.In the fœtus, the foramen ovale and the ductus arteriosus also render very evidently the arteries and veins continuous; in the fœtus the heart is likewise a simple organ, not forming, notwithstanding its partitions, but one cavity whilst it is double after birth. The two kinds of blood mix at this period, as in reptiles. Now, I shall prove hereafter, that in the child who has breathed, this mixture would soon be fatal; that the black blood, circulating in the arteries, would very quickly produce asphyxia in the animal. Whence arises then this difference? It cannot be studied in the fœtus; it is necessary perhaps to search for it in frogs, salamanders and other reptiles, which can, by their organization, be a long time deprived of air without dying, a phenomenon which approximates them to the mammalia while living in the womb of the mother. Till these very important researches are made, the history of respiration will be incomplete.
[48]I am persuaded that the still very obscure theory of the fœtus might be elucidated by that of animals who have a similar organization. For example, in the frog, in whom but little blood goes through the lungs, the heart is a simple organ, with a single auricle and ventricle; there is a communication or rather continuity between the two systems, venous and arterial, whilst in the mammalia, the vessels in which the red blood circulates do not communicate with those which carry the black blood, except it be by the capillaries.
In the fœtus, the foramen ovale and the ductus arteriosus also render very evidently the arteries and veins continuous; in the fœtus the heart is likewise a simple organ, not forming, notwithstanding its partitions, but one cavity whilst it is double after birth. The two kinds of blood mix at this period, as in reptiles. Now, I shall prove hereafter, that in the child who has breathed, this mixture would soon be fatal; that the black blood, circulating in the arteries, would very quickly produce asphyxia in the animal. Whence arises then this difference? It cannot be studied in the fœtus; it is necessary perhaps to search for it in frogs, salamanders and other reptiles, which can, by their organization, be a long time deprived of air without dying, a phenomenon which approximates them to the mammalia while living in the womb of the mother. Till these very important researches are made, the history of respiration will be incomplete.
[49]This explanation is no doubt ingenious, but it is insufficient, since the causes which Bichat assigns for the rapidity of the growth of the fœtus cease entirely at the moment of birth, and yet the growth continues for a long time after to be as rapid.
[49]This explanation is no doubt ingenious, but it is insufficient, since the causes which Bichat assigns for the rapidity of the growth of the fœtus cease entirely at the moment of birth, and yet the growth continues for a long time after to be as rapid.
[50]When two phenomena are seen to follow each other immediately, we are naturally led to consider one as the cause of the other.Post hoc ergo propter hoc.It is a form of reasoning which is very often abused. Food taken into the mouth touches the orifice of the salivary ducts, the fluid flows out, and it is then concluded that the salivary gland has been excited by the impression made on the extremity of its canal. At the moment of birth, the orifice of the urethra is exposed to the contact of the air, and soon the kidneys begin to secrete; then it is the impression of the air on the urethra that has produced their action. But is not this contact of the food in the one case, and of the air in the other an accidental and purely accessory circumstance? Do we believe, that if by any cause the opening of the prepuce was entirely obliterated, the secretion of urine would be prevented? Do we not know that if instead of taking into the mouth savoury food, it is brought near to it, the saliva flows not less, or in vulgar language the mouth waters? There is however no contact, there is not any mechanical or chemical impression in the orifice of the salivary ducts.
[50]When two phenomena are seen to follow each other immediately, we are naturally led to consider one as the cause of the other.Post hoc ergo propter hoc.It is a form of reasoning which is very often abused. Food taken into the mouth touches the orifice of the salivary ducts, the fluid flows out, and it is then concluded that the salivary gland has been excited by the impression made on the extremity of its canal. At the moment of birth, the orifice of the urethra is exposed to the contact of the air, and soon the kidneys begin to secrete; then it is the impression of the air on the urethra that has produced their action. But is not this contact of the food in the one case, and of the air in the other an accidental and purely accessory circumstance? Do we believe, that if by any cause the opening of the prepuce was entirely obliterated, the secretion of urine would be prevented? Do we not know that if instead of taking into the mouth savoury food, it is brought near to it, the saliva flows not less, or in vulgar language the mouth waters? There is however no contact, there is not any mechanical or chemical impression in the orifice of the salivary ducts.
We have just now seen, that the two lives commence at distant epochs; we have seen them developing themselves according to laws, which are exactly the reverse of each other. I shall now attempt to describe them, as they terminate; and this they do in a very different manner also, assuming characters at such time as distinct and separate, as those which they possess during the periods of their activity. In this place, I shall speak of natural death only; those deaths, which originate in accidental causes, will be the object of the second part of this work.
Natural death is remarkable for the following reason chiefly:—it terminates the animal life, a long time before it puts an end to the organic life.
He who dies in consequence of a very prolonged old age, dies in detail; his exterior functions are finished, one after the other; the senses are shut up successively; the ordinary causes of sensation pass over them, and do not affect them.
The sight grows dull and confused; it ceases at length to transmit the images of objects: this is the blindness ofold age; sounds also, after a certain time, affect the ear confusedly; the organ at last becomes entirely insensible. The cutaneous covering of the body grows hard and dry; it is the seat of an obscure and imperfect touch. Besides which, the habitude of feeling has blunted the power of feeling; at the same time all the other organs which are dependent on the skin, grow weak and perish; the hair falls, it is deprived of the juices by which it was nourished: to continue our description, odours make but a feeble impression upon the nostrils.
The taste indeed is a little more kept up; but let it be remarked that this sense is connected with the organic as much as with the animal life, and is therefore necessary to the internal functions: In this way, when all agreeable sensations have fled the old man, when their absence has already broken in part the connexions, which attach him to the world, his taste remains with him still; it is the last thread to which is suspended the pleasure of existence.
In this way, isolated in the midst of nature, already deprived of the greater number of the functions of the sensitive organs, the old man is soon to suffer the loss of the common action of the brain, for it is manifest, that there can scarcely be any farther perception, for the very reason that there is nothing farther coming from the senses. Meanwhile, the imagination lessens and is soon annihilated.
The memory of present things is destroyed: the old man in an instant forgets what is told him, because his external senses enfeebled and already dead, as it were, in no wise confirm what is intimated to him by the mind alone. Ideas escape him when the images, which are traced by the senses, do not keep their hold. On the contrary, the remembrance of the past remains with him,that which the old man has formerly known, has been taught him or at least confirmed to him by his senses.[51]
He differs from the child in this respect; the child judges only from the sensations which he experiences, the old man from those, which he has experienced.
The result of the two states is the same, for the judgment is equally uncertain, whether founded exclusively upon actual or past sensation. Its accuracy depends upon the due comparison of the two. No one can be ignorant, that in the judgment which we form from visible objects, the actual impression would frequently deceive us, were we not to rectify the error by what we are enabled to recollect, and may we not observe that past sensations, in a short time grow confused, if the features of the picture, which they have left with us, be not retraced by new and analogous impressions?
The present then, and the past with regard to sensation, are equally necessary for the perfection of the judgment. If either the one or the other be wanting there cannot be any comparison made between the two, and in consequencethere must be a want of precision in the judgment.
For these reasons, the first and the latter ages of man, are equally remarkable for imbecility. Old age is second infancy. The two periods of life resemble each other with regard to want of judgment; they differ only as to the cause of such defect.
The interruption of the functions of the brain of the old man, is a consequence of the almost entire annihilation of the sensitive system with him; in the same way does the weakness of the locomotive power, succeed almost inevitably to the inactivity of the brain. This organ in fact re-acts upon the muscles, in proportion only as the senses act upon it.
The movements of the old man are few and tardy; he changes with difficulty the attitude, into which he has thrown himself; seated near the fire, and concentrated within himself, a stranger to every thing without him, he passes his days there, deprived of desire, of passion, and sensation; speaking little because he is determined by nothing to break his silence, yet happy in feeling that he still exists, when almost every other sentiment is gone.
The rigidity of the muscles however, and the diminution of their contracting powers, is another cause of inactivity in the old man, and doubtless has its influence; but it is by no means the principal one, since the heart and the muscular fibres of the intestines, contract the same rigidity, and are deprived of their powers of moving, in a very different way from that, in which the voluntary muscles lose it. With the voluntary muscles, it is not so much the power as the excitant of the power which is lost. If it were possible to compose a man with the senses and brain of old age, and the muscles ofyouth, the voluntary motions of such man, would hardly be more developed for the reasons which I have given.
From the above it is easy to see that the external functions of the old man are extinguished by degrees, and that his animal life has almost entirely ceased, while his organic life is still in activity. Under this consideration, the state of the animal about to suffer a natural death, is nearly similar to that of the fœtus in utero, or of the vegetable which lives within itself only, and for which external nature is absolutely silent.
If we now recollect that sleep entrenches more than a third upon the duration of the animal life, if we add to this the total absence of such life for the first nine months of existence, and its almost entire inactivity during the latter period of existence, it will be easy to calculate the great disproportion of its duration, when compared with that of the organic life which is exercised uninterruptedly.
But wherefore when we have ceased to exist without, do we continue to exist within, since our sensations and above all, our powers of locomotion, are especially destined to place us in relation with those substances, which are to nourish us. Wherefore are those functions enfeebled in a greater disproportion than the internal functions, and why is there no exact relation in the times of their cessation.
I cannot entirely resolve this question. I shall only observe that society has an especial influence in creating this difference; for man in the midst of his fellow-creatures makes a very great use of his animal life; the springs of it are habitually more fatigued than those of his organic life, and worn away under the influence of society; the eye by artificial light, the ear by sounds too frequently repeated, and above all by those of speech,which are wanting to other animals;[52]the smell in like manner is debilitated by factitious odours, the taste by savours, which certainly are not natural, the touch and the tact by constant attrition of dress,[53]and the brain by too incessant thinking.
We live then externally with excess. We abuse our animal life; it is circumscribed by nature within limits which are too much enlarged by us for its duration; thus it cannot be surprising that it should cease so soon. In fact we have seen the vital powers divided into two orders, the one appertaining to this life, the other to the organic life. These two orders may be compared to two lights which burn at the same time, and which have only a determined quantity of materials for aliment. In which case, if the one be agitated by a stronger wind than the other is, it must necessarily be the sooner extinguished.
Yet social influence notwithstanding is very advantageous to man. It gradually disengages him from those bonds which attach him to life, and renders the instant of death less terrible.
The idea of our last hour, is painful only because it puts an end to our animal life. The borders of the tomb are beset with terrors, which will all be found to originate in the thought of such privation.
It is not the pain of death, which we fear; how many dying men are there for whom the gift of existence would be precious, though purchased at the expense of an uninterrupted series of suffering! If we look at the animal which lives but little externally, he by no means trembles at beholding the instant of his death.[54]
Were it possible to suppose a man, who in dying should lose his internal functions only, such man would look upon his death with an indifferent eye, because he would feel that the blessings of existence, are attached to the powers of feeling the influence of nature and society.
If the animal life then be terminated gradually, if each of the bonds by which we are capable of the pleasures of living, be broken by little and little, such pleasures will escape us imperceptibly, and the old man will have forgotten the value of life, when it is about to be taken from him; such destruction will resemble that of the vegetable only.
The organic life remains with the old man after the almost total loss of his animal life, and terminates in a very different manner from that which is exemplified in the case of violent and sudden death. The latter has two periods, the first of which is marked by the sudden cessation of respiration and the circulation, the secondby the slow and gradual extinction of the other organic functions.
The parietes of the stomach, for instance, continue to act upon the aliment which may be found there, the juices of the stomach continue to dissolve it. The experiments of the English and Italian physicians upon absorption, (experiments the whole of which I have repeated) have proved that this function not unfrequently remains in a state of activity, after the general death of the body, and if not as long as some have supposed, at least for a very considerable interval. Discharges of urine and feces are often observed to take place many hours after sudden death.
The process of nutrition also continues to be manifest in the hair and in the nails; the same would doubtless be the case in all the other parts, as well as in the secretions, could we observe the insensible movements of which their functions are the result. The heart of the frog being taken away, the capillary circulation may still be seen under the influence of the tonic powers. The body is very slow also in losing its animal heat.[55]
I might augment the above observations with a number of others, which would go to prove the same assertions; onthe contrary, in the death which is the effect of old age, the whole of the functions cease, because they have each of them been successively extinguished. The vital powers abandon each organ by degrees, digestion languishes, the secretions and the absorptions are finished, the capillary secretions become embarrassed; lastly, the general circulation is suppressed. The heart is the ultimum moriens.
Such, then, is the great difference which distinguishes the death of the old man, from that which is the effect of a sudden blow. In the one, the powers of life begin to be extinguished in all the parts, and cease at the heart; the body dies from the circumference towards the centre: in the other, life becomes extinct at the heart, and afterwards in the parts. The phenomena of death are seen extending themselves from the centre to the circumference.
FOOTNOTES:[51]If the old man preserves with difficulty the memory of the most recent events, whilst he often retraces with the greatest ease the recollection of the most distant ones, it is not because the first have been more faithfully transmitted to him by his senses, but because these events had produced a greater impression on him. This is so true, that failure of the memory is sometimes remarked in old people who have their senses in perfection. On the other hand, very imperfect sensations may produce a very lively impression. A connoisseur in painting, when his sight is very bad, experiences in seeing a beautiful picture, a hundred times more pleasure, than one who is indifferent to it, though he examines it with good eyes, and the connoisseur preserves the image of it long after the other has lost it. We do not perceive the recollection of things, unless there is some circumstance connected with them that makes a lively impression; but in the same event, this circumstance will not be the same in all individuals, and it is sometimes by the most trifling of all that a man fixes the fact in his memory.[52]This failure of the senses appears in animals as well as man, and it may be observed in those whom we suffer to grow old among us. We often see dogs becoming blind and deaf; and these infirmities are perhaps more common in them than in man. But as these animals are rarely permitted to arrive at extreme old age, we have not often an opportunity of observing them.[53]By defending the skin from the shock of external bodies, and by preserving it from the variation of temperature, dress very certainly preserves its sensibility, and far from impairing the sense of touch, as Bichat maintains, it acts as a circumstance favourable to its preservation.[54]The animal no doubt does not tremble at the moment of death; for he does not see it. His present sensation is every thing to him. If he suffers at the approach of death, he shows it by the usual signs; but it is only the present pain that he expresses, he sees nothing beyond. The child is in this respect, in the same situation as the animal.[55]In order to ascertain the cause of the differences in the cooling of the body after the various kinds of death, it is necessary to examine what general conditions can have an influence in the cooling of a body left to itself. Of these there are three principal ones.Under the same external circumstances, a body will cool so much the slower. 1st. As its temperature at the beginning of the experiment, shall be higher in relation to that of surrounding bodies; 2d. As its surface shall be less in relation to its size; 3d. And as its exterior parts shall be less perfect conductors of heat.In order to see how the first condition is modified in different cases, it is necessary to recollect what is the source of animal heat. The blood is warmed in passing through the lungs in consequence of the chemical phenomena of respiration; and as from the lungs it is carried to all parts of the body, it yields to the different organs a portion of the heat which it has received. Hence the general temperature of the body will be higher in proportion to the temperature of the blood, to the frequency with which this fluid is renewed in the organs and to the quantity of it that is brought to them, at each pulsation.Now in diseases of long duration, the volume of blood is considerably diminished, the activity of the heart is lessened, and respiration is performed in an imperfect manner. Thus the body of the patient who sinks under these circumstances has less heat to lose than that of the man who dies suddenly, when all these functions were performed in perfection.Let us pass now to the second condition. The cooling, as we have said, takes place so much the quicker as the surface of the body is the more extended in proportion to its size; now, in the emaciation which accompanies almost all diseases that are protracted, the size decreases much more rapidly than the surface. Thus then, when even at the moment of death the general temperature of the body may be as high as in a state of health, the cooling would however take place more quickly.It remains for us now only to examine under what circumstances the third condition is fulfilled in the most advantageous manner. When an individual in full health dies, the sub-cutaneous cellular texture usually contains a greater or less quantity of fat. Now we know that it is one of the characters of all fat substances to be very bad conductors of heat. Hence then a third reason which should render cooling more slow after sudden deaths. Sometimes after a disease, this last condition is fulfilled in another manner. In certain derangements of the circulation, the cellular texture is filled with serum; and as all aqueous fluids are bad conductors of caloric, though the temperature of the body may not be very high at the moment of death, the heat is yet preserved for a long time.To the different causes which we have just mentioned, there is sometimes added another which is peculiar to one kind of sudden death. It is observed that in the midst of the same external circumstances, the blood does not always cool with the same quickness, and that in proportion as its coagulation is slower, its heat is longer preserved. Now, it is a well known fact, that when death is the result of asphyxia, the vessels are found full of fluid blood; this is also a reason which contributes to explain the slowness of the cooling. And it should be remarked, that asphyxia is one of the most frequent causes of sudden death either accidental or voluntary.
[51]If the old man preserves with difficulty the memory of the most recent events, whilst he often retraces with the greatest ease the recollection of the most distant ones, it is not because the first have been more faithfully transmitted to him by his senses, but because these events had produced a greater impression on him. This is so true, that failure of the memory is sometimes remarked in old people who have their senses in perfection. On the other hand, very imperfect sensations may produce a very lively impression. A connoisseur in painting, when his sight is very bad, experiences in seeing a beautiful picture, a hundred times more pleasure, than one who is indifferent to it, though he examines it with good eyes, and the connoisseur preserves the image of it long after the other has lost it. We do not perceive the recollection of things, unless there is some circumstance connected with them that makes a lively impression; but in the same event, this circumstance will not be the same in all individuals, and it is sometimes by the most trifling of all that a man fixes the fact in his memory.
[51]If the old man preserves with difficulty the memory of the most recent events, whilst he often retraces with the greatest ease the recollection of the most distant ones, it is not because the first have been more faithfully transmitted to him by his senses, but because these events had produced a greater impression on him. This is so true, that failure of the memory is sometimes remarked in old people who have their senses in perfection. On the other hand, very imperfect sensations may produce a very lively impression. A connoisseur in painting, when his sight is very bad, experiences in seeing a beautiful picture, a hundred times more pleasure, than one who is indifferent to it, though he examines it with good eyes, and the connoisseur preserves the image of it long after the other has lost it. We do not perceive the recollection of things, unless there is some circumstance connected with them that makes a lively impression; but in the same event, this circumstance will not be the same in all individuals, and it is sometimes by the most trifling of all that a man fixes the fact in his memory.
[52]This failure of the senses appears in animals as well as man, and it may be observed in those whom we suffer to grow old among us. We often see dogs becoming blind and deaf; and these infirmities are perhaps more common in them than in man. But as these animals are rarely permitted to arrive at extreme old age, we have not often an opportunity of observing them.
[52]This failure of the senses appears in animals as well as man, and it may be observed in those whom we suffer to grow old among us. We often see dogs becoming blind and deaf; and these infirmities are perhaps more common in them than in man. But as these animals are rarely permitted to arrive at extreme old age, we have not often an opportunity of observing them.
[53]By defending the skin from the shock of external bodies, and by preserving it from the variation of temperature, dress very certainly preserves its sensibility, and far from impairing the sense of touch, as Bichat maintains, it acts as a circumstance favourable to its preservation.
[53]By defending the skin from the shock of external bodies, and by preserving it from the variation of temperature, dress very certainly preserves its sensibility, and far from impairing the sense of touch, as Bichat maintains, it acts as a circumstance favourable to its preservation.
[54]The animal no doubt does not tremble at the moment of death; for he does not see it. His present sensation is every thing to him. If he suffers at the approach of death, he shows it by the usual signs; but it is only the present pain that he expresses, he sees nothing beyond. The child is in this respect, in the same situation as the animal.
[54]The animal no doubt does not tremble at the moment of death; for he does not see it. His present sensation is every thing to him. If he suffers at the approach of death, he shows it by the usual signs; but it is only the present pain that he expresses, he sees nothing beyond. The child is in this respect, in the same situation as the animal.
[55]In order to ascertain the cause of the differences in the cooling of the body after the various kinds of death, it is necessary to examine what general conditions can have an influence in the cooling of a body left to itself. Of these there are three principal ones.Under the same external circumstances, a body will cool so much the slower. 1st. As its temperature at the beginning of the experiment, shall be higher in relation to that of surrounding bodies; 2d. As its surface shall be less in relation to its size; 3d. And as its exterior parts shall be less perfect conductors of heat.In order to see how the first condition is modified in different cases, it is necessary to recollect what is the source of animal heat. The blood is warmed in passing through the lungs in consequence of the chemical phenomena of respiration; and as from the lungs it is carried to all parts of the body, it yields to the different organs a portion of the heat which it has received. Hence the general temperature of the body will be higher in proportion to the temperature of the blood, to the frequency with which this fluid is renewed in the organs and to the quantity of it that is brought to them, at each pulsation.Now in diseases of long duration, the volume of blood is considerably diminished, the activity of the heart is lessened, and respiration is performed in an imperfect manner. Thus the body of the patient who sinks under these circumstances has less heat to lose than that of the man who dies suddenly, when all these functions were performed in perfection.Let us pass now to the second condition. The cooling, as we have said, takes place so much the quicker as the surface of the body is the more extended in proportion to its size; now, in the emaciation which accompanies almost all diseases that are protracted, the size decreases much more rapidly than the surface. Thus then, when even at the moment of death the general temperature of the body may be as high as in a state of health, the cooling would however take place more quickly.It remains for us now only to examine under what circumstances the third condition is fulfilled in the most advantageous manner. When an individual in full health dies, the sub-cutaneous cellular texture usually contains a greater or less quantity of fat. Now we know that it is one of the characters of all fat substances to be very bad conductors of heat. Hence then a third reason which should render cooling more slow after sudden deaths. Sometimes after a disease, this last condition is fulfilled in another manner. In certain derangements of the circulation, the cellular texture is filled with serum; and as all aqueous fluids are bad conductors of caloric, though the temperature of the body may not be very high at the moment of death, the heat is yet preserved for a long time.To the different causes which we have just mentioned, there is sometimes added another which is peculiar to one kind of sudden death. It is observed that in the midst of the same external circumstances, the blood does not always cool with the same quickness, and that in proportion as its coagulation is slower, its heat is longer preserved. Now, it is a well known fact, that when death is the result of asphyxia, the vessels are found full of fluid blood; this is also a reason which contributes to explain the slowness of the cooling. And it should be remarked, that asphyxia is one of the most frequent causes of sudden death either accidental or voluntary.
[55]In order to ascertain the cause of the differences in the cooling of the body after the various kinds of death, it is necessary to examine what general conditions can have an influence in the cooling of a body left to itself. Of these there are three principal ones.
Under the same external circumstances, a body will cool so much the slower. 1st. As its temperature at the beginning of the experiment, shall be higher in relation to that of surrounding bodies; 2d. As its surface shall be less in relation to its size; 3d. And as its exterior parts shall be less perfect conductors of heat.
In order to see how the first condition is modified in different cases, it is necessary to recollect what is the source of animal heat. The blood is warmed in passing through the lungs in consequence of the chemical phenomena of respiration; and as from the lungs it is carried to all parts of the body, it yields to the different organs a portion of the heat which it has received. Hence the general temperature of the body will be higher in proportion to the temperature of the blood, to the frequency with which this fluid is renewed in the organs and to the quantity of it that is brought to them, at each pulsation.
Now in diseases of long duration, the volume of blood is considerably diminished, the activity of the heart is lessened, and respiration is performed in an imperfect manner. Thus the body of the patient who sinks under these circumstances has less heat to lose than that of the man who dies suddenly, when all these functions were performed in perfection.
Let us pass now to the second condition. The cooling, as we have said, takes place so much the quicker as the surface of the body is the more extended in proportion to its size; now, in the emaciation which accompanies almost all diseases that are protracted, the size decreases much more rapidly than the surface. Thus then, when even at the moment of death the general temperature of the body may be as high as in a state of health, the cooling would however take place more quickly.
It remains for us now only to examine under what circumstances the third condition is fulfilled in the most advantageous manner. When an individual in full health dies, the sub-cutaneous cellular texture usually contains a greater or less quantity of fat. Now we know that it is one of the characters of all fat substances to be very bad conductors of heat. Hence then a third reason which should render cooling more slow after sudden deaths. Sometimes after a disease, this last condition is fulfilled in another manner. In certain derangements of the circulation, the cellular texture is filled with serum; and as all aqueous fluids are bad conductors of caloric, though the temperature of the body may not be very high at the moment of death, the heat is yet preserved for a long time.
To the different causes which we have just mentioned, there is sometimes added another which is peculiar to one kind of sudden death. It is observed that in the midst of the same external circumstances, the blood does not always cool with the same quickness, and that in proportion as its coagulation is slower, its heat is longer preserved. Now, it is a well known fact, that when death is the result of asphyxia, the vessels are found full of fluid blood; this is also a reason which contributes to explain the slowness of the cooling. And it should be remarked, that asphyxia is one of the most frequent causes of sudden death either accidental or voluntary.
BICHAT ON LIFE AND DEATH.
In the first part of this work, I have explained the two great divisions of life, together with the remarkable differences, which distinguish the animal existing without, from the animal existing within. I have discussed the characters which are exclusively proper to the two lives, and the particular laws, according to which they both of them commence, are developed and end in the natural order.
In this second part I shall inquire in what way they accidentally finish, in what way their course is prematurely arrested.
The influence of society suffers us but rarely to live out the period which was intended us by nature; while almost every other animal attains his natural end, such end in the human species is become a sort of phenomenon. The different kinds then of accidental death, should engage the particular attention of the physician and physiologist. Now this sort of death may happen in two ways: sometimes it is the result of great disturbance excited in the economy; and sometimes it is the effect of disease.
In general it is easy enough to discover, according to what laws the functions are terminated in consequence ofany violent or sudden attack; of apoplexy, for instance, great hemorrhagy, concussion of the brain, or asphyxia; because in such cases the organs of the body, excepting that which is immediately affected, are not the seat of any peculiar lesion, and cease to act from causes diametrically the contrary of those, which according to the common course of things maintain them in action. Now as these causes are partly known, their contraries may be inferred; besides, we are capable of imitating these sorts of death upon animals, and consequently of analyzing, experimentally, their different phenomena.
On the other hand it is seldom in our power to produce artificially in the bodies of animals the diseases of the human species. Were we even possessed of such power, we should gain but little knowledge from it: the laws of life in fact are so changed, so modified, so altered in their very nature, by the various morbid affections to which the parts are subject, that but very seldom can we depart from the known phenomena of the living animal, when we undertake to inquire into those which it exhibits in its dying moments. For such inquiries it would be necessary to know what is that intermediate state between health and death, in which the functions experience so remarkable a change; a change, which has such infinite varieties, and produces such innumerable sorts of disease. But, where shall we find the physician, who will assert that from the actual data of his art, he understands in such intermediate state, the profoundly hidden operations of nature?
In these researches then, we shall occupy ourselves more especially on those sorts of death which I first enumerated. Those, which have been mentioned in the preceding paragraph will engage us only now and then: besides, at my age I cannot be supposed to have acquireda sufficient degree of medical knowledge to treat of them with advantage.
The first remark, which the observation of the different kinds of sudden death suggests, is, that in all of them the organic life to a certain point may subsist, the animal life being extinct; but that the latter is entirely dependent, and lasts not for a moment after the interruption of the former. The individual, who is struck with apoplexy may live internally for many days after the stroke, externally he is dead. In this case death commences with the animal life: if on the contrary it exerts its influence in the first place upon any of the essential organic functions—as on the circulation in wounds or on respiration in the asphyxiæ—the animal life is gone at once, together with the sensible actions of the organic life.
The red and warm-blooded animal, loses his external life at the moment when he ceases to exist internally, the cessation of the phenomena of his organic life is a sure index of his general death; indeed the reality of death can be pronounced only from such datum; the interruption of the external phenomena of life is in almost every instance fallacious.
On what depends this difference of the manner in which the two lives accidentally end? It is owing to the mode of that influence, which they exercise the one over the other, to the kind of bond, by which they are connected.
This mode of influence, this bond, appears to exist between the brain on the part of the animal life and the lungs, or heart on the part of the organic life. The action of one of these three organs is essentially necessary to that of the two others; and as they constitute the three centres, in which are terminated all the secondary phenomena of the two lives, whenever they cease to act, thephenomena which depend upon them must cease also, and general death ensue.
Physiologists have been at all times acquainted with the importance of this triple focus; and have given the name of vital to all those functions, which have their seat in it. Under the point of view which at present engages our attention their ideas on this head are well worthy of notice, for every species of sudden death begins by the interruption of the circulation, the respiration, or action of the brain. In the first place, one of the three functions ceases, then the others successively; so that to expose with precision the phenomena of sudden death, we must consider them as they take place in the three principal organs, which we have mentioned.
We shall first inquire into those deaths, which begin at the heart, and afterwards into those, which begin in the lungs and in the brain. I shall explain in what way, when one of these organs is affected, the others die; and then demonstrate by what sort of mechanism the death of the various other parts of the body ensues. Lastly I shall determine from the principles, which I shall then have laid down, the nature of the different species of disease, which are peculiar to the heart, the lungs, and the brain.
I shall evidently have determined what is the mode of this influence, should I be enabled to establish in whatway the action of the heart is necessary to that of the brain; for in this instance the cause of death will be no other than the privation of the cause of life. Now the heart can only act upon the brain in two ways; by the nerves, or the vessels which serve as their connecting medium. In fact these two organs have no other means of communication.
It is evident that the nerves cannot be the agents of such actions; it is the province of the brain to act by means of the nerves. The different parts of the body never influence the brain by such means, excepting in the sympathies. If a bundle of nerves belonging to the voluntary muscles be tied, the muscles indeed will cease to act, but nothing will be changed in the cerebral mass.[56]
I have ascertained by many experiments that the phenomena of galvanism, which are propagated so energetically from the brain towards the organs, which descend, if I may so express myself, along the nerve, will hardly ascend in a contrary direction. Apply the apparatus to a nerve of the loins and the muscles of the upper limbs, and when the communication is made, there will be scarcely any contraction; but on the establishment of a communication between the same nerve and the lower limbs, a violent convulsive motion will instantly be occasioned. I have even observed, on placing two metallic plates, the one under the lumbar nerves, and the other under the upper limbs, that the communication of the two plates by means of a third metal, will cause a contractionof the lower limbs, while the upper limbs remain inactive, or move but feeble.[57]
These experiments are particularly applicable to the relation of the heart with the brain; for not only is it true that the section, ligature or compression of the cardiac nerves are of little effect with regard to the functions of the latter, but it is true also, as we shall presently see, that they do not directly modify the movements of the former. We may conclude that the vessels are the exclusive agents of the influence of the heart upon the brain.
The vessels, as every one knows, are of two sorts—venous or arterial—they carry black or red blood, the latter answer to the left side, the former to the right side of the heart. Now their functions being very different, the action of one of the portions of this organ on the brain, can never be the same as that of the other portion. We shall inquire in what way they both of them act upon it.
In naming these two portions, I shall not make use of the expressions of right and left to distinguish them, but of those of the red-blooded and the black-blooded heart, for each of these portions of itself is an isolated organ, distinct from that to which it is applied, and in the adult especially so. In fact there are two hearts, the one arterial, the other venous, notwithstanding which, we can hardly employ these adjectives for the purpose of designating them, since they both alike possess their arterial and venous appendages. On the other hand, they are neither of them situated exactly to the right or to the left, areneither of them exactly forwards or backwards. Besides which these latter denominations would not apply to animals.
The red-blooded ventricle and auricle, exert their influence upon the brain by means of the fluid which they send thither through the carotid and vertebral arteries. This fluid may excite the cerebral organ in two ways. 1st. By the movement, with which it is directed. 2nd. By the nature of its colouring principle.
It is easy to prove that the movement of the blood is necessary to the life of the brain. Expose the brain of an animal in part, and tie the carotids. In such case the cerebral movement will be sometimes weakened, and then the animal will be stupified, at other times the vertebral arteries will exactly supply the place of the carotids, and then there will be nothing deranged in the principal functions of the brain; for there is always a relation existing between the alternate rise and fall of the cerebral mass, and the energy of life which it displays.[58]
In general, the obliteration of the carotids is never suddenly mortal. Animals will live without them, at least for a certain time. I have kept dogs in this statefor several days and have afterwards made use of them for other experiments: two however died in the course of six hours, after the application of the ligatures.
After having made the above experiments which go very far to the establishment of the principle which I am labouring to prove, let a piece of the cranium be taken from another animal and tie the vertebral and carotid arteries. The movement of the brain will then be entirely interrupted and the animal immediately die.
The impulse, which proceeds then from the influx of the blood into the brain, is a condition essential to the functions of this organ, but other proofs may be adduced, for the establishment of the truth of this assertion.
1st. There are a number of compressions, which can only act by preventing the brain from being duly affected by such impulse. A collection of pus, or blood, will often put a stop to all the functions, which relate to the perception, memory, and voluntary motions of the individual. Let such compression be removed and his sensibility will immediately re-appear. In such case, it is manifest that the brain was not disorganized, but only compressed, and in a state incapable of being excited by the heart.[59]
I do not think it necessary on this subject to cite cases. All authors, who have treated of wounds of the head, are full of them. I shall content myself with remarking, that the same effect may be artificially produced in our experiments upon animals, and that accordingly as the brain is compressed or free, the creature will be insensible,or the contrary. According to the degree of the compression, will be the degree of the stupor.
2dly. There are reptiles, in the brain of which no motion whatever is occasioned by the heart. The frog is of this species. On raising the upper portion of the cranium, and exposing the brain, there cannot be perceived the slightest motion. Now in this species, and that of the salamander, the influx of blood may be cut off from the cerebral organ without occasioning the immediate death of the animal. The voluntary muscles for instance continue to act; the eyes to exhibit a lively appearance, the tact also of the creature is manifest for some time after the heart has been taken away, or the double branch which proceeds from the single ventricle of these animals has been tied.[60]I have frequently repeated these experiments, and have constantly found the effect the same.
3rd. It is a general observation, that those animals which have a long neck, and in which the heart for that very reason is not so capable of exerting a lively influence over the brain, have a more limited intellect, and the cerebral functions less marked. On the contrary a very short neck, and the approximation of the heart to the brain very generally are found to coincide with the latter. Similar phenomena are sometimes observed in men. They who have the neck particularly long are dull, they who have it short, for the most part intelligent and lively.
From these many facts we may confidently assert, that one of the means, by which the heart maintains the brain in action, consists in the habitual movement, which it impresses on it.
But this movement is essentially different from that which in the other viscera, such as the liver, or spleen, is derived from the same cause. In these it is little manifest, in the brain it is very apparent; the reason is evident; the large arterial trunks of the brain, are situated at its base, between the brain and its bony parietes; in consequence of which, at each diastole, the vessels experience a resistance from the bone, which is communicated immediately to the cerebral mass. At such time the brain is really lifted, just in the same way as we see a tumour lifted by the arteries which creep along the bones beneath it; and instances of this are frequent. So apparent indeed is the motion of tumours when they are situated over the carotid, as it lies upon the vertebral column, or over the femoral artery, immediately after its passage under the crural arch, as often to occasion doubts with respect to their nature.
But no other organ is enclosed within a bony cavity; the motion of the arteries every where else, is lost in the surrounding cellular substance, or soft parts. Such motion, then, is unessential to the functions of the liver, the kidney, and other analogous viscera.
The integrity of the functions of the brain, is not only dependent on the mere motion, but on the sum also of the motion communicated. It is equally impaired by too much, or by too little motion. Of this assertion the following experiments are proofs.
1st. Inject water by the carotid of a dog; the presence of this fluid in the brain is not pernicious, and the animal will live very well, when the injection has been skilfullymade. But if it be pushed with violence, the cerebral action will immediately be troubled, and often cannot be restored.[61]In every experiment, there will be found to exist a relation between the force of the impulse and the state of the brain; if the pressure be but a little augmented, its effects will be instantly seen in the agitation of the countenance of the creature; if relaxed, a corresponding calm will succeed; if increased to the highest pitch, it will immediately occasion death.
2dly. If the brain be exposed, and an artery afterwards opened, so as to produce a considerable hemorrhage, the motion of the brain will be diminished in proportion as the afflux of the blood to it is diminished, and finally will cease entirely. Now, according to all these various degrees of diminution, which may be observed in the movements of the brain, will be the corresponding weakness of the cerebral influence as it is discoverable in the state of the eyes, the touch, and the voluntary motion of the animal.[62]
Hence it is easy to see, why a state of prostration and languor is always the consequence of great hemorrhage—andfrom what has been said above we may conceive the reason, why the arterial system of the brain has been at first concentrated at its base, while the larger venous trunks are almost all of them situated on the convexity of its surface. The base of the brain is small and easily moved, the convexity large and little capable of transmitting motion, such as could be made upon it by vessels. Besides, it is at the lower part of the brain that exist its particular and essential forms. The lesions of these are mortal, and consequently their functions must be important. On the contrary, experiment and observation alike have proved, that very little derangement follows, from cutting or rending the substance of the upper part of this organ. Hence also we may see the reason, why its natural defences towards its base, are constituted in such way as to be almost impenetrable, and why at its upper surface, it is less protected. Now, where its life is indispensable, and its action absolutely necessary, it should naturally receive the first and undiminished impulse of its excitant. We may conclude, that the interruption of the action of the red-blooded heart is the occasion of interruption in the action of the brain by annihilating its movement.
But this movement is not the only means by which the influence of the heart is exerted on the brain; for if it were so, we might easily reanimate the enfeebled functions of the latter, by injecting it with water at the same time through both the carotids. If pushed with an equal force, the black blood and the red blood alike would be capable of keeping up its action; but this, as we shall presently see, is not the fact.
The heart, then, acts upon the brain by the nature of the fluid which it sends thither; but as the lungs are the focus, where the blood undergoes an alteration, we shallrefer the examination of its influence upon the cephalic system, to the chapter in which we shall treat of the relation of this system, with that of the lungs.
It very rarely happens that general death commences by that of the venous auricle and ventricle. On the contrary, they are almost always the last in action, and when they cease to act, the brain, the lungs, and the red-blooded heart have already ceased to exhibit their respective phenomena. Nevertheless the contraction of these cavities may be annihilated, or rendered at least inefficacious with regard to the circulation, from the rupture of an aneurism or similar causes; in which case the brain becomes inactive and dies, as we have shewn it to do in the preceding section, from want of movement.
There is another kind of death of the brain depending on the interruption of the transmission of blood from the head to the heart, as when the jugulars are tied. The venous system, in consequence, is glutted and the brain compressed, from the continued afflux of the red blood into its arteries; but the phenomena of this sort of death are already sufficiently known.
In the present chapter it is my intention to examine a species of death, the principle of which by many physiologists has been placed in the heart, but which appears to me to affect the head only; I mean that death which may be occasioned by the injection of air into the veins.
It is generally known, that as soon as any quantity of this fluid is introduced into the vascular system, the movements of the heart are accelerated, that the creature is much agitated, cries with pain, is convulsed, and soon after deprived of its animal life, but lives organically for a certain time, and then invariably dies.[63]Now, what is the organ so readily affected by the contact of air? I affirm it to be the brain, and not the heart; and maintain that the circulation is annihilated, only because the cerebral actions have previously been so.
For, in the first place, in this kind of death, the heart continues to beat for some time after the cessation of the animal life, and consequently for some time after that of the action of the brain.[64]
Secondly, By injecting air into the brain through one of the carotids, I have caused the death of the creature just in the same way as when air is introduced into theveins; excepting only with a previous palpitation of the heart.[65]
Thirdly, Morgagni has cited a number of cases of sudden death, the cause of which should appear, from his remarks, to be the repletion of the blood vessels of the brain by air, which had been developed there spontaneously, and which he says, by its rarefaction, compressed the origin of the nerves. I cannot suppose that such compression can be effected by the very small quantity of air, which, when injected into the carotid, is sufficient to occasion death; accordingly, I should doubt whether this compression were real in the cases adduced, but for this, they are not the less important. Whatever be the manner in which it kills, air is fatal whenever introduced into the brain, and this is the essential point. It is with the fact that we have to do and not the manner.[66]
Fourthly, As often as an animal is killed by the insufflation of air into one of its veins, I have ascertained thatthe whole of the red-blooded, as well as the black-blooded heart, is full of a frothy blood, mixed with air bubbles;and that the carotids, and vessels of the head, contain a similar blood; such blood must act upon the brain, in the same manner as it does in the two sorts of apoplexy, of which we have just been making mention.
Fifthly, If air be pushed into one of the divisions of the vena portæ from the side of the liver, it oscillates in the greater trunks of that organ for a considerable length of time, and arrives but slowly at the heart.—In this instance I have observed, that the animal experiences, only after a certain interval, those affections which are sudden when the fluid is injected into the veins of the principal system.[67]
Sixthly, The rapidity with which, in certain experiments, the annihilation of the cerebral action succeeds to the insufflation of air into the veins, might almost persuade us that such phenomenon is occasioned, as it is in wounds of the heart and syncope;—but 1st. The most simple inspection is sufficient to shew us that the heart continues to act after the apparent death of the animal.—2dly. As the motions of the heart are prodigiously accelerated by the contact of the foreign fluid, they push on the frothy blood with an extreme velocity, and hence we have the reason, why the brain in such case is so rapidly affected.
Seventhly, Were the cerebral action in this sort of death interrupted for want of movement from the heart, it would happen as it does in great hemorrhages of the aorta; that is to say, without violent convulsion. But here, on the contrary, the convulsion is extremely violent, immediately after the injection, and consequently,announces the presence of an irritating substance on the brain.
We shall conclude, that in the accidental mixture of air with the blood of the venous system, it is the brain which dies the first, and that the death of the heart is the consequence of the death of the brain. I shall explain in another place, in what way this phenomenon is occasioned.