CHAPTER VIII.

OF THE INFLUENCE OF THE DEATH OF THE LUNGS OVER THAT OF THE ORGANS IN GENERAL.

I have just shewn in what way the interruption of the chemical phenomena which take place in the lungs, annihilates the functions of the heart and brain. It remains me to shew, that the other organs of the body are as much affected by such cessation; so that asphyxia, as I have said, is a general disease, and not an affection of any one organ in particular.

But before I proceed to analyze the effects of asphyxia upon the organs in general, and consequently the mode of action of the black blood upon them, it may be of use to explain the phenomena of the production of this kind of blood, at the instant when the functions of the lungs are suspended. This paragraph will possess, perhaps, some interest; it might have belonged indifferently to either of the preceding chapters.

I. _Exposition of the phenomena of the production of black blood, when the chemical functions of the lungs are suspended._

It is known in general, that the blood is coloured in traversing the lungs, that from black it becomes red; but this very interesting fact, has not been hitherto the object of any precise or rigorous experiment. The lungs of the frog, of which the air vessels are large, and the membranes thin and transparent, would serve very well for the purpose of observing the process of the phenomenon in question, but for the slowness of respiration in these animals, the difference of organization in their lungs, and the too small quantity of blood by which they are traversed. On such account there can be little analogy between them and the more perfect animals, and then again our experiments upon these little amphibiæ, are all of them rendered incomplete, by the tenuity of their pulmonary vessels, and the impossibility of observing the correspondence of the change of velocity in the circulation, with the colour of their blood.

The phenomena of the respiration of man, and those of the functions which are dependent on it, can be illustrated only by experiments made upon animals with a double ventricle, with a complete pulmonary apparatus, possessed of a temperature superior to that of the atmosphere, and the two separate systems of venous and arterial blood; but on the other hand, in the mammalia resembling man, their respiratory apparatus, the thickness of the vessels and cavities of the heart, impede the view of the blood which they contain; and experiments made without an absolute inspection of the fluid there, can only give us approximations. The indecisive experiments of former physiologists on this subject were my motives for the present inquiry.

One of the best methods of judging of the colour of the blood, consists as I have often said, in fixing a tube with a stop-cock to the trachea. By this, the influx of air into the lungs, may be regulated or altogether stopped. By this, we may distend the organ, or entirely evacuate it; it gives us also the facility of introducing whatever gas we please. The animal breathes very well by such pipe when it is open, and would live with it for a considerable length of time without any very great alteration in its functions.

In the second place, an artery, the crural or carotid for instance, must be opened with the view of observing the varieties of colour in the blood projected from it. A small artery should not be chosen. From such a one the course of the blood would be suspended by the slightest accident; and on the other hand, the larger arteries expend in a little time too large a quantity of blood; this inconvenience may be remedied, by adapting to these vessels a tube of a small diameter, or a stop-cock.

All things being thus prepared, on a dog, for instance, let us see what are the phenomena which take place, when the colour of the blood is altered. In my indication of these, however, I shall speak only of what I have seen, and by no means pretend that in man their duration should be similar or uniform, or even that in animals of the same species, under the different circumstances of sleep, digestion, exercise, and passion, &c. if it were possible in such way to repeat them, they should be alike. The instability of the animal functions, as I have said, is extreme; they cannot be submitted to calculation; they remain indeed the same, but their variations as to plus or minus are innumerable.

Let us now return to our subject:

1st. If the cock of the pipe be shut immediately after the animal has inspired, the blood begins to be altered in colour at the end of about thirty seconds.--At the end of a minute its colour is dark; at the end of a minute and half or two minutes, it is perfectly similar to venous blood.

2dly. If the cock of the pipe be shut immediately after the animal has expired strongly, the blood receives its tinge of black some seconds the sooner.

3dly. If the air of the lungs be pumped out entirely with a syringe, the blood will suddenly pass from red to black.[94] In such case it appears that the artery immediately throws out a black stream, after it has expelled the red blood which it previously contained. There is no gradation. The blood is expelled by the arteries, such as it is in the veins.

4thly. If, instead of making a vacuum in the lungs, we inflate the air cells to the full, the blood is a longer time in becoming black, a minute at least, and is not completely black before the end of three minutes.--This will vary according to the quantity of air injected.

From all these experiments it follows, 1st, That the length of the interval, during which the blood retains its red colour, is in direct proportion to the quantity of air contained in the lungs; 2dly, That as long as there remains any quantity however small of respirable air in the cells of the lungs, the blood will preserve more or less of its crimson colour; 3dly, That this colour diminishes in proportion as the respirable air diminishes; and 4thly, That the blood is exactly similar to that of the veins, as soon as the whole of the vital air in the extremities of the bronchiæ has been exhausted.

In my different experiments with regard to asphyxia, I have remarked, that if after shutting the cock of the syringe, the animal agitate the chest by similar movements to those of inspiration and expiration, the blood is a longer time in losing its red colour, than in the case where the breast remains at rest. Such motion and agitation must cause a circulation of air in the cells, in consequence of which, a greater number of its points must be presented to the circulating fluid. My experiments which I shall presently detail on the breathing of animals in bladders, will prove the truth of the above explanation.

At present I pass to a contrary set of phenomena--to those which are exemplified when the blood regains its arterial colour during the period, which, from a state of asphyxia, restores the animal to life.

1st. When the cock, which for some minutes has been shut, is opened, the air immediately penetrates into the bronchiæ; but previously the animal expires strongly. Six or seven large inspirations and expirations follow each other precipitately. The artery being now examined, a jet of a very vivid colour is seen succeeding to the efflux of black blood, and takes place in thirty seconds at most, from the time of opening the tube. This is the inverse of the phenomenon above described. There are no successive shades perceived from black to red; the passage is instantaneous. The brightness of the colour seems even to be greater than is natural.

2dly. If instead of suddenly turning the cock, a very strong stream of air only be admitted, the colour is less lively indeed, but just as quickly regained.

3dly. If there be adapted to the stop-cock a syringe full of air, and this fluid be pushed into the lungs, on opening the pipe, and then the pipe be suddenly shut again, the blood will become red, but much less evidently so, than when the entrance of the air is owing to voluntary inspiration. Here the portion of air injected must repel into the bottom of the cells whatever is already vitiated, while on the contrary, if the tube be simply opened, the vitiated air is at once rejected, and then replaced from without. The following experiment appears to confirm this idea.

4thly. If instead of pushing air upon that which is contained in the lungs, we pump out the vitiated air in the first place, and then inflate the organ, the colouring process will be more rapid, and the colour of the blood itself especially, more lively than in the preceding case, though less so than in the first of this latter suite of experiments.

5thly. The lungs being exposed on both sides by a lateral section of the ribs, the circulation will continue to go on for a certain time. Now, if by means of a syringe adapted to the stop-cock in the trachea, the pulmonary vesicles be alternately emptied and dilated, the changes from red to black, and from black to red, will be observed as in the above experiment, as long as the circulation lasts.

The following consequences may be inferred from the facts, which I have mentioned.

1st. The rapidity with which the blood becomes red again, on opening the pipe in the trachea, is a plain proof, that the principle from which this colour is gained, must pass into the blood across the membranous parietes of the air cells, and not by means of the absorbents. I shall establish this fact hereafter upon other proofs.

2dly. The celebrated experiment of Hook, in which the enfeebled movements of the hearts of animals in a state of asphyxia are accelerated by injecting air into the lungs, is very well explained. The red blood penetrates into the fibres of the heart, and puts an end to the debility induced, by the influx thither of the black blood.

3dly. I do not believe, that motion can ever be restored to the heart, when once it has been wholly annihilated by the presence of venous blood. In this I have never succeeded, though I have often attempted it. Many authors, however, pretend to have done so. If the heart be reanimated by arterial blood, it is necessary at any rate, that such blood, should pass into it, now in what way can it arrive there, if the circulation have entirely ceased.

We must observe, however, that there are two cases of interruption in the action of the heart from asphyxia. Sometimes there supervenes a syncope which arrests the movement of this organ, before the black blood has been able to produce such effect; and here it is manifestly capable of excitement, from the presence of the red blood, just as it is from the application of any irritating cause; but when it has been injected with venous blood, it then contains within itself the principle of its inertia, which can be removed only by the contact of arterial blood with it; but such contact is become impossible.

I was very desirous of knowing what the influence might be of the different gases when inspired upon the colour of the blood. Accordingly I successively adapted to the pipe different bladders, containing hydrogen and carbonic acid gas.

The animal alternately swells and contracts the bladder by the different motions of the thorax. It is calm at first, but at the end of three minutes, begins to be agitated; its respiration is now hurried and embarrassed, and at the end of four or five minutes, the blood of the carotid is black.

Whichever of the two gases be employed, there is little difference in the above phenomena. This remark should be compared with those of the Members of the Institute, who have assured us that complete asphyxia supervenes only after an interval of ten minutes, with pure hydrogen, and at the end of two minutes with carbonic acid gas. The black blood must continue, therefore, to circulate for a longer time in one than in the other kind of asphyxia here spoken of. This circumstance confirms some reflections which I shall have occasion to offer upon the difference of asphyxiæ.

For what reason should the blood be a longer time in losing its colour, when bladders of non-respirable air are fixed to the pipe, than when the cock is simply turned? The reason of this is evident. By the different motions of the lungs, the air is expelled and reabsorbed, the respirable portion of it must consequently be successively presented to the capillary orifices, by which it is transmitted to the blood.

On the contrary, when the pipe is simply shut, the air it is plain has not the same influx and efflux; in comparison with such motion, it may be said to stagnate so that the respirable portion of that which is enclosed in the bronchial cells is exhausted, and the blood ceases to be coloured, though there remain in the trachea and its larger divisions, a considerable quantity of fluid, which has not been despoiled of its vivifying principle. Of this we may be certain, after the death of the animal, by cutting the trachea under the pipe, and plunging a bougie into it. The process by which the blood gains its red colour appears to take place only at the extremities of the bronchiæ, the inner surface of the larger aerial vessels, has nothing to do with this phenomenon.

We may convince ourselves of the reality of the explanation which I have offered, if we pump out the air of the lungs, before we fit the bladder to the trachea; for in such case, the animal must breathe the air of the bladder without mixture. Here the change of the blood to black is almost sudden, but here also, as in the preceding experiment, there is little difference in the phenomena, whatever gas we employ. I have chosen the two gases above mentioned, because they enter into the phenomena of natural respiration.

When we adapt to the pipe a bladder full of pure oxygen, the blood is very long in becoming black, but does not at first assume a redder tint than it usually has.

II. _The blood which has been blackened in consequence of the interruption of the chemical functions of the lungs penetrates into the organs, and circulates for some time in the vascular system of the red blood._

We have just established what are the phenomena of the alteration of colour in the blood, when the chemical functions of the lungs are suspended. Before we consider the influence of this change upon the death of the organs, let us prove, that they are really penetrated by the blood when so altered.

I have proved it to be a fact, that the force of the heart subsists for some time, notwithstanding the influx of the black blood into it, and have shewn that the black blood is thrown out with a jet, similar to that of the red blood, &c. &c. Hence I might already conclude, 1st, That the arterial circulation continues for a certain time, though the arteries contain a fluid, to which they are not accustomed, and 2dly, That the necessary consequence of such circulation, must be the injection of the different parts of the body with black blood; but we shall deduce the latter conclusion from precise and rigorous experiments. To be certain of this important fact, we have only to expose successively the different organs, while the animal is suffering a death of asphyxia. I have in this way examined the muscles, the nerves, the membranes and the viscera. The following are the results of my observations.

1st. The colouring matter of the muscles, exists in the body in two states--at liberty, or in a state of combination; in the vessels, where it circulates with the blood, or in the fibres, with which it is combined. It forms especially the colour of the muscles, and in such state undergoes no alteration from asphyxia; in its free state it is blackened. The divided muscles furnish an infinity of black drops, which are no other than indices of the divided vessels. Such drops contrast with the red of the muscles; but when circulating within them, are the cause of that livid tint which they then present.

2dly. The nerves are habitually penetrated by a number of small arteries, which creep along within their tissue, and carry to them both excitement and life. In the state of asphyxia the black blood by which they are traversed, is announced by the dull brown, which succeeds to the rosy-white, which is natural to them.

3dly. There are few parts, where the influx of the black blood is more visible, than in the skin; the livid spots so frequent in asphyxia, are only the effect of the obstacles which it meets with, in its passage towards the general capillary system, to the organic contractility of which it is not a sufficient excitant. To this cause also is owing the tumefaction of certain parts, such as the cheeks and lips. This phenomenon we have seen already in the lungs, they cannot be traversed by the blood and therefore become in the last moments of life, the seat of a fulness, which affects the whole of the capillary system there; but for the reasons, which I have assigned, such fulness is always more evident in the capillary system of the lungs, than in that of the system in general.

4thly. The mucous membranes also, when the chemical functions of the lungs are interrupted, exemplify a similar phenomenon. The swelling of the tongue, observable in those that have been drowned or hanged, or asphyxiated by the vapour of charcoal, the lividity of the membrane of the mouth, of the intestines, and the bronchiæ which have also been remarked, depend on no other cause. The following is a proof of this assertion:

Drag out of an animal a portion of the alimentary canal and divide it in such way as to expose its inner surface. Then shut up the pipe which has been previously adapted to the trachea, and at the end of four or five minutes, a brown tint will succeed to the red one, which is natural to this surface.

5thly. I have made the same remark upon the fleshy granulations of a wound, inflicted on an animal, for the purpose of observing the manner in which they are coloured by the black blood. In the two last experiments, this phenomenon is slower in taking place than in many other circumstances.

6thly. The alteration of colour in the serous membranes is much more quickly effected than it is in the mucous membranes. Of this we may assure ourselves by comparatively examining the outer and inner surfaces of the intestines, while the pipe in the trachea is shut; in the serous membranes, the livid tint which they assume, depends upon the vessels, which creep underneath them, and not on the blood by which they are penetrated. Now as these vessels are considerable, the black blood must flow into them almost as soon as it is produced. In the mucous membranes on the contrary, and in all cicatrices, the colour which they take on in asphyxia, is made by the capillary system of the membrane itself, which system is much more tardy than the other, to receive the black blood, and to be penetrated by it; so much so indeed, as to refuse it in some parts. I have many times seen the membrane of the nasal fossæ very red in asphyxiated animals, while that of the mouth has been quite livid, for there are parts into which as I have said the black blood will not penetrate at all, and then they preserve their natural colour. 2dly. There are others into which it evidently passes, but where it stops, and then a simple change of colour is observed, if it have penetrated but in small quantity; and again, if it have penetrated in a considerable quantity, together with such change of colour, there will be observed a tumefaction of the part. 3dly. In other cases, the black blood merely traverses the parts, without stopping in the capillary system, and passes at once into the veins, as the red blood does.

In the first and second case, the general circulation experiences an obstacle which puts a stop to it in the general capillary system. In the third, which is much more universal, it is in the capillaries of the lungs that the blood is at last arrested, after having circulated in the veins.

These two sorts of impediment coincide with each other, in many instances. Thus in asphyxia, a part of the black blood which circulates in the arteries stops in the face, upon the mucous surfaces, in the tongue, and in the lips, while the other, and much the larger quantity, finds no impediment in the general capillary system, and is finally arrested in the lungs.

What is the reason, why certain parts of the capillary system refuse to admit the venous blood, or if they admit it, do not pass it on to the veins; while others are less enfeebled by it, and transmit it as freely as ever. All this must certainly depend on the relation existing between the sensibility of each part and the venous blood.

I was desirous of making use of the power, which we possess, of changing the colour of the blood, for getting some insight into the influence of the circulation of the mother, upon that of the fœtus; accordingly I procured a bitch big with young, and asphyxiated her, by closing a tube, adapted to the trachea. About four minutes after she had ceased to breathe, I opened her; the circulation was going on. I then cut into the matrix, and exposed the cord of two or three of the fœtuses. The artery and the vein, were both of them full alike of venous blood.

Had I been able to procure other bitches in a similar state, I should have repeated this experiment in another manner. I should in the first place have compared the natural colour of the vein, with that of the artery. In many of the young of the guinea pig, the difference appeared to me to be much less than it is in the adult animal. In many circumstances indeed I could perceive no difference whatever. Both the arterial and venous blood were equally black, though the respiration of the mother was in no wise impeded by the opening of the belly. Secondly, I should have closed the tube in the trachea, and then have observed whether the change in colour of the umbilical artery of the fœtus (supposing the blood of the artery to be different from that of the vein) were correspondent with that, which would inevitably take place in the blood of the mother. Experiments made with a view to these circumstances, and on large animals, might probably throw much light upon the mode of communication, between the mother and the fœtus. Observations are also much to be desired, with respect to the colour of the blood in the human fœtus, and the cause of its passage from a livid colour, to the very marked red which it assumes, some little time after birth.[95]

I might add a number of examples to these, which I have already related of the blackening of the organs by the venous blood. Thus, the kidney of a dog exposed, while the animal is dying of asphyxia, is much more livid than in its natural state, the spleen also and the liver, when divided, emit only black blood, instead of that mixture of red and black blood which is observable, in the section of these organs, upon an animal which breathes freely.

But I trust that we have facts enough to establish it as a certainty, 1st, That the black blood after the interruption of the chemical functions of the lungs, continues for some time to circulate, and 2dly, That it penetrates into the organs, where it replaces the red blood; these circumstances explain the reason, why on opening the body we always meet with black blood even in the vessels which are destined for the circulation of arterial blood.

In the last moments of existence of whatever death the individual may have died, we shall always observe the lungs become embarrassed and cease to perform their office, for some time previous to the total suspension of the functions of the heart. The blood makes its circle through the system, after ceasing to receive the influence of the air, and consequently in its venous state; accordingly it must remain so in the organ in every case, although the circulation be much less evident, than in asphyxia, for it is in this circumstance that consists, the great peculiarity of asphyxia. The following phenomena may now be easily understood.

1st. When the left auricle and ventricle together with the large divisions of the aorta, on opening the body, are found to contain blood, such blood is always black. The fact is familiar to those who are in the habit of dissecting. In exercising my pupils on the surgical operations, I have always observed that when the open arteries are not entirely empty, their contents are composed of venous blood.

2dly, The corpus cavernosum is always gorged with this sort of fluid, whether flaccid or in a state of erection. For I have seen it in the latter state in two subjects brought to my amphitheatre. One of these men had hanged himself, the other had died of concussion of the brain.

3dly, The blood which is found in the spleen is never red; but sometimes on the exterior, and sometimes on the concave surface of this organ, I have observed spots of a scarlet colour, for which I cannot account.

4thly, After death, the mucous membranes lose the red colour by which they are characterized during life. They assume a black and livid hue.

5thly, Blood extravasated in the brain of persons in a state of apoplexy, is almost always found to be black.

6thly, Sometimes, instead of accumulating inwardly the blood injects the surface of the body. In such case the face, the neck, and shoulders swell, and are infiltrated with blood. I have frequently remarked this sort of phenomenon in the subject, but have never found it coincide with any internal extravasion.--The colour of the skin is then of a purple or deep brown, an evident sign of the sort of blood with which it is injected, and is evidently produced by the stagnation of the black blood in the external capillary system, not by the reflux of the blood from the veins.

I shall not dwell any longer upon the numerous consequences of the above established principle. I shall only observe, that when death commences by the circulatory system, the preceding phenomena are not to be remarked, or at least very little perceptible.

Let us now pass on to the influence of the black blood upon the organs of which it penetrates the tissue.

III. _The black blood which penetrates the organs, as soon as the chemical functions of the lungs have ceased, will not maintain them in a state of life and activity._

To determine what the influence of the black blood is upon the organs, I shall first remark, that the property of the red blood is to stimulate them, and keep up their vital actions. This will be proved by the following observations:

1st, Compare phlegmon, erysipelas, and inflammatory tumours (to the formation of which the red blood is essentially requisite) with scorbutic spots, and petechiæ, produced by the black blood. The first will be found connected with the exaltation of the vital powers, the second with their depression.

2dly, Examine two men, the one with a rosy coloured skin and large breast, announcing vigour of lungs, the other with a pale and sallow countenance, and narrow chest: in these the vigour of the chemical combinations which are made in the lungs, should certainly be very different.

3dly, The greater number of gangrenes in old men, begin with a lividity in the part, a lividity which is evidently the index of the absence or diminution of the arterial blood in the part.

4thly, The redness of the branchiæ of fish is always the sign by which their vigour may be recognised.

5thly, The redder the granulations of wounds, the more healthy is their nature; the paler or browner they are, the less has the part a tendency to cicatrise.

6thly, The lively colour of the face, and the ardent eye, coincide with the energy of the cerebral actions in certain fevers.

7thly, The more developed the pulmonary system of animals, the more active are the chemical processes of the lungs, and the more developed and perfect the general life of their different organs.

8thly, Youth, which is the age of vigour, is that also when the red blood predominates in the system. The arteries of old people are smaller, the veins larger than those of the young. It is a fact universally known, that at the two extremities of life the proportions of the two vascular systems are inverted.

I am ignorant of the manner in which the red blood excites and keeps up the life of the parts. Perhaps the principles by which it is coloured become combined with the different organs to which it is distributed. In fact there is a considerable difference between the phenomena of the general and those of the capillary system.

In the first, the blood in changing its colour, leaves behind it the principles which made it red; in the second, the elements to which its blackness is owing, are rejected by respiration and exhalation. Now, this union of the colouring principles of the arterial blood, may probably constitute a material part of the excitement which is necessary to the action of the organs.--If such be the case, the black blood as it does not contain the materials of such union, cannot act as an exciting cause. This idea, however, I offer only as a probability, and am by no means prepared to defend it as a truth; it may be ranked on a par with that of the sedative action, which I have said may be excited by the black blood on the different parts--for, however probable an opinion may appear, there should be no real importance attached to it as an opinion only.

Without regard then to any system, let us inquire how the black blood, from its contact with the various parts, is the occasion of their death; how it acts on the parts of the animal life, and how it acts on those of the organic life.

All the organs of the animal life depend upon the brain; now, we have seen that the black blood paralyses the cerebral powers almost suddenly. In the state then of asphyxia, the locomotive, the vocal and sensitive organs, must be inactive. From the same cause, their exercise must be suspended in all those different experiments where black blood is injected into the brain, the other parts receiving the red blood as usual. But when the black blood circulates throughout all the system, when the whole of the organs, as well as the brain, are submitted to its influence, then there are two other causes of death connected with those which have been mentioned.

1st, The nerves, which are penetrated by it, for that very reason are no longer capable of keeping up the communication between the brain and the senses on the one hand, and on the other, between this same viscus and the locomotive or vocal organs.

2dly, The contact of the black blood with these organs themselves annihilates their actions. Inject the crural artery of an animal with the black blood taken from one of its veins, and the movements of that member will be shortly afterwards enfeebled, or wholly paralyzed. In this experiment, the upper part of the artery, for manifest reasons, should be that to which the pipe of the syringe should be fixed.

I am aware that as to this experiment, it may be asserted that the ligature of the artery, of itself, is capable of paralyzing the limb. In fact, such circumstance has happened twice with me, but I have also had occasion to observe, that it does not necessarily follow the ligature of this vessel, as it does the ligature of the aorta: when the latter vessel is tied, all movements cease at once; notwithstanding all which, the result of the injection of black blood, is almost constantly that which I have asserted it to be;--I say almost, 1st, Because I have once seen it fail in its effect, though done with the requisite precautions; 2dly, Because the debility, which is induced, both in duration and degree, will be according to the strength of the animal on which the experiment is made.

There is also occasioned in this experiment, a manifest suspension of the sensibility of the animal; it is not indeed so ready to appear as the loss of motion; but it always comes on, especially if the injection of the black blood be repeated three or four times, with small intervals.

A similar, but a more tardy effect may be produced by adapting to the canula, which has been placed in the crural artery of an animal, a tube which has been previously fixed to the carotid of another animal, and then by asphyxiating the latter.[96] The organs of the internal life are not dependent on the brain, and therefore are not affected by the suspension of the cerebral action in asphyxia. It is the influx of the black blood which is the immediate cause of their death.

I have already demonstrated what the influence is of this blood upon the organs of the circulation. We have seen how the heart ceases to act, as soon as it is penetrated by it; it is owing in part to the injection of the arterial and venous parietes themselves, by the vasa vasorum, that the vessels are forced to suspend their actions.

It will be always a difficult thing to prove, that the secretions, the exhalations, and the process of nutrition, could not be made from venous blood, because the circulation of this sort of blood in the arteries, does not continue for a sufficient time, to allow of observations, or the manner in which these functions would be affected by it. On this subject, however, I have made some essays. 1st, I exposed the inner surface of the bladder of a living animal, after having previously divided the symphysis pubis, and opened the lower belly, I then examined the oozing of the urine from the orifices of the ureters, while I asphyxiated the animal. 2dly, I divided the vas deferens, with the view of observing, whether the semen would flow or not, during such state.

In general, I have had occasion to remark, that during the circulation of the black blood in the arteries, no fluids appear to issue from the different secreting tubes. But I confess, that in all these experiments, and in other similar ones which I have made, the animal is too much agitated, and the limits of the experiments too circumscribed, for any thing like a well founded judgment to be formed on the subject in question. It is chiefly from analogy, then, that I am led to conclude, that the black blood is unfit for the purposes of exhalation and nutrition: such supposition also accords well with divers of the phenomena of asphyxia.--1st, The want of exhalation from the skin during the state of asphyxia, is probably the reason of the phenomena of the animal heat in such sort of death.[97] 2dly, In asphyxiating animals very slowly during digestion, I have uniformly observed, that the bile ducts, and duodenum, contain a much less quantity of bile, than they do at such time, when these parts are exposed in the living animal.--3dly, As the blood loses nothing from the exercise of these functions, it must of course accumulate in the vessels; and in fact, it is very fatiguing and unsatisfactory, to dissect the bodies of those who have been hanged or asphyxiated with the vapours of charcoal, from the fluidity and abundance of their blood. But this abundance, perhaps, may depend upon the weakness of the absorbents. In other sorts of death, the absorbents continue for some time to act upon the serous portion of the blood remaining in the vessels. In asphyxia there is neither secretion nor absorption.

The excretions also appear to be affected much in the same way. The bladder of asphyxiated persons has been observed by Portal, to be very much distended. Such distension, no doubt is occasioned by the urine already secreted before the accident which was the cause of their deaths. In general, the asphyxiæ which are occasioned by the circulation of the black blood unmixed with any deleterious substance, are not accompanied with those spasms, which in so many other sorts of death, are so frequent. These spasms, which evacuate the organs of their fluids, should be carefully distinguished from the simple relaxations of the sphincters, by which analogous effects are produced.[98] In asphyxia, all is debility, in asphyxia, we never see that augmentation of life, that development of power, which so frequently mark the latter movements of the dying.

Hence also perhaps, the great flexibility of the members of asphyxiated persons. The stiffness of the muscles appears to depend in many cases, on the circumstance of death having come on precisely at the moment of their contractions. The fibres remain approximated, and coherent among themselves;[99] in asphyxia, on the contrary, as there exists an universal relaxation and want of action in the parts, they remain so after death, and yield to whatever impulse may be communicated to them.

I confess, however, that this explanation is subject to a difficulty which I cannot solve. Persons asphyxiated by mephetic vapours, perish nearly in the same way as those who are drowned; if the cause of their death be different, its effects are the same, as may be seen by opening the carotid of two dogs at the same time, that into the lungs of the one are injected the vapours of charcoal, and into those of the other, a certain quantity of water, which water, as in the drowned, is soon reduced into a state of foam.

Notwithstanding this similitude of the last phenomena of life in the two cases, the members in the first remain for a certain time warm and supple, while those in the second, especially if the body be plunged into water during the experiment, become very suddenly stiff and frozen. Let us return, however, to our subject. We may conclude from the various facts and considerations related in this chapter, 1st, That when the chemical functions of the lungs are suspended, the functions of all the other organs are suspended also, from the presence of black blood within their substance. 2dly, That the death of the organs in general, coincides with that of the brain, and the heart, but is not immediately derived from them. 3dly, That if it were possible for the brain and heart to receive an influx of arterial blood, while the others were dying, from that of the venous blood, they would doubtless continue to exert their accustomed actions. 4thly, That, in a word, asphyxia is a general phenomenon, developed at the same time in all the organs, but especially in one of them.

From this manner of regarding the influence of the black blood upon the different parts of the body, it appears that death is very soon the result of its circulation in the arteries. Nevertheless, certain organic defects have sometimes prolonged after birth, the mixture of the two sorts of blood, a mixture which is known to be made in the fœtus. Such was the malconformation mentioned by Sandeford, in a child, the aorta of which arose by a branch from each of the ventricles. Such also appears, at first sight, to be the opening of the foramen ovale in the adult.

We shall remark, however, that the existence of this foramen, does not suppose the passage of the black blood into the red-blooded auricle, as is generally believed. For the two semi-lunar valves, between which it is situated when met with after birth, are necessarily applied to each other by the pressure which the blood contained in the auricles, exercises upon them, when these cavities are simultaneously contracted. The foramen must be at such time shut, and its obliteration much more exact, than that of the opening of the ventricles, by the mitral and tricuspid valves, or that of the aorta and the pulmonary artery, by the sigmoid valves. With all this, the foramen ovale is actually very often found open in the subject, and when not so, nothing is easier than to destroy the species of adhesion which is contracted by the two valves which close it. This may be done with the handle of a scalpel, without any solution of continuity, the parts appear to be unglued.

The oval hole when in this way artificially made, presents the same disposition, with that which is sometimes exemplified in the carcase. Now if this disposition be examined, it will be seen that when the auricles contract, the blood must make an obstacle to itself, and that it cannot pass from one into the other of these cavities. It is an easy thing to be convinced of the mechanism of which I speak, by means of two injections of a different colour, made at the same time from both sides of the heart, from the vena cava, and the pulmonary veins.

From what we have said of the influence, which is exercised by the movement and the different principles of the blood, it is evident that the death of the white organs must be different from that of the red ones. Asphyxia can hardly reach them, but of the manner in which they die I confess that I know but little.

FOOTNOTES:

[94] It is not possible to remove by this means a great portion of air contained in the lungs, for the last ramifications of the air-tubes being flexible, their parietes soon come in contact, and thus oppose the exit of the air contained in the bronchial cells.

[95] These observations have been made on the great mammalia, and there has not been remarked any difference of colour.

[96] The difference that is remarked in the results of this experiment, compared with that in which the venous blood is introduced by means of a syringe, arises probably from this, that in the first the blood that is forced into the artery has already begun to coagulate.

[97] The deficiency of cutaneous exhalation in the last moments of life may contribute a little perhaps to the preservation of animal heat; but we have shown that there are other more powerful causes for this phenomenon. This deficiency of exhalation united to the inaction of the secretory organs, in the very short period in which the black blood runs in the arteries is an altogether insufficient cause to explain the abundance of blood that is found in the vessels of those who have died of asphyxia.

[98] This is not an uniform fact, and it is even very common to find, in persons who have been hung, the bladder completely empty.

[99] The moment respiration ceases, and the source of heat is consequently cut off, it is not astonishing that an animal body should become cold quicker in water then in a much less dense fluid, like the air. It should also be remarked that the water, on account of the evaporation that takes place on its surface, has almost always a temperature below that of the surrounding air.