« AnteriorContinua »
deavour to show that part of the foetal structure remaining in adult life, has little influence in deranging the health, unless some additional cause arises.
In examining the cases mentioned by authors who treat of diseases of the heart, we find sufficient proof to convince us, that, on dissection, many appearances of altered structure have presented themselves, which, from the state of symptoms during life, we never should have suspected. In these cases, little variation will be found to have taken place in the relative size of the cavities of the heart.
We have already noticed, that the foramen ovale is found open so frequently, that anatomists look on it as a matter of little consequence. The observation only holds true, however, where the relative size of the auricles remains the same; for the moment the right increases in size or strength, or any other derangement of the lesser circulation is added, the most distressing symptoms supervene.
The explanation seems to be this.-As long as both auricles receive and discharge the same relative quantity of blood, no mixture to any extent can take place, even although the foramen ovale be very large; but when the right becomes either smaller, or of increased strength, or the left is seized with what is called passive aneurism, a portion of blood must go through to support the equilibrium. If the tricuspid valve, or the lungs themselves, become diseased, the same changes must happen.
The above reasoning applies equally to cases where the septum of the ventricles is perforated. It seems probable, that, in our patient, the little variation that was found in the relative size of the heart was the cause of her surviving so long, and that death was produced from the adhesions of the lungs, and the increased strength of the right auricle. In the case also mentioned by Corvisart, the increased size of the right auricle, and other disease of the lesser circulation, were in all probability the causes of death.
In proof of the above mode of explanation, the following facts may be brought forward.
In many infants, a few days before death, a partial or general blueness is observed on the surface. In most of these that were examined, the foramen ovale was open. Such observations I have found to be very numerous. In the last case that was examined, the child had been troubled with convulsions for several days before death. Each of these lasted for some time; and though the breathing and pulse continued, the surface became generally livid, and retained partly that hue during the rest of the day. The foramen ovale was found very large. In all these
cases, where the extinction of life is gradual, the extremities first become cold; the intellectual functions cease; and a vast accumulation of blood is always found in the lungs, which, as Bichat has proved, is owing to the capillaries of that organ retaining their activity much longer than in any other part of the body. A diminished supply of blood must therefore reach the left cavities of the heart; so that, in order to support the equilibrium, as much as is sufficient must go through the foramen ovale; and hence the blueness follows.
Another proof of the dangerous consequences that arise from the foramen ovale remaining open, is afforded by the cases of infants, where, soon after birth, some cause arises to impede the free circulation of the blood; for in that instance the foetal state of circulation in part recommences. The following examples seem to favour this opinion.
A child a few days old, of a very weak state of body, began suddenly to labour under great difficulty of breathing, became feverish and very fretful. The body was much emaciated, with general blueness over the surface; pulse quick and feeble; breathing slow and laborious, so as nearly to suffocate the child. The death was very sudden.
Dissection showed the brain natural, but the surface loaded with black blood. The lungs of the left side were very hard, and in many places nearly white; other parts were of a much redder colour. They seemed to have received but little blood, and scarcely any air. There was considerable effusion into the thorax. The right lung was perfectly natural; the pericardium full of serum; the foramen ovale and ductus arteriosus but little diminished from the size they have at the ninth month; the heart was injected with blood.
A child born at six weeks before the full period, remained tolerably well till the second week, when repeated fainting fits came on, and the body assumed a livid appearance. The fits were very frequent each day, and scarcely was one finished when another gradually came on. They lasted from ten to sixteen minutes. During them the child ceased to respire, but the pulse continued regular, though feeble. The lips first assumed the livid appearance, and were the first parts to recover their natural state. Great relief was found from using the warm bath and fomentations when the fit was expected. They seemed to shorten the period. The child continued to have these attacks for three days, but eventually recovered, and never has had the least indication of them since, though still very feeble.
In both of these cases, the foetal circulation was probably in part renewed; only in part, however; for the foramen ovale and
ductus arteriosus are so much contracted at the ninth month, that a considerable part of the blood must pass through the lungs before birth. We might ascertain this with more accuracy by weighing the lungs of the foetus at different periods. At birth, just before the child respires, the weight of the lungs, to the whole body, is nearly; after respiration or In the earlier stages of the foetus, it will probably be found that the difference is much greater, and we may discover that the foramen ovale becomes smaller.
Vieussens relates the case of a child that was well formed, and lived for 36 hours, and on dissection not a trace of the foramen ovale was to be found.
In cases where the child is born after a very severe labour, the foetal state of circulation is said to continue for some time. Of this, however, I have had no opportunity of judging.
The experiments of Count Buffon, who endeavoured to make animals amphibious that were not so naturally, are too vague to be made use of in supporting the fact of the continuance of the foetal state of circulation.
From what has been stated, we may perhaps be convinced that part of the foetal structure may remain till adult life, without producing any very material derangement; but that the moment the relative uniformity of the lesser circulation is destroyed, the most marked symptoms arise, which speedily terminate in death. Admitting these conclusions, we easily explain the cause of our patient's enjoying good health for so long a period, which was the subject we undertook to prove,
From the circumstance of universal blueness which was observed in our patient, we may be induced to bring it forward, as several authors have done, as a symptom pathognomonic of diseased heart. This opinion is not altogether accurate; for in your Journal some years ago, I remember reading a case accurately detailed by Dr Marcet, of general blueness during life, yet nothing but strong and universal adhesion of the lungs was found on dissection. To this observation let me add two others of nearly a similar nature.
A girl 21 years of age, of a very delicate constitution, and liable to cough during the winter, happened to get wet feet during menstruation, which increased all her complaints, and in six months great difficulty of breathing. The menses ceased entirely; her hands became cedematous; and the whole surface of the body acquired a tint of blueness in one day. She could now only breathe on her back, with her head raised. Pulse 120, After using blisters for some time, the colour became much more intense, and she died very suddenly. All the symptoms in
dicated diseased heart; yet on dissection it was quite sound ; but the lungs adhered at every point, and the veins were gorged with black blood.
The second case originated also from suppression of the menUniversal blueness followed immediately, aggravated on using exercise; her health gradually decayed, and she died in three years. Great adhesions of the left lung, especially to the pericardium; right lung adhered also; the left auricle and ventricle seemingly enlarged, full of blood of a dark colour; the right side healthy.
Most authors have insisted on disease of the right side of the heart as a uniform cause of blueness; and the mechanical idea of the blood being driven with increased celerity through the capillaries of the lungs, has been offered as a satisfactory expla nation. Blueness does certainly occur more frequently when the right side of the heart is diseased, than in other cases; but then the livid appearance does not depend on the mechanical intermixture of blood, but arises merely from the stagnation occasioned in the veins of the head and extremities; and the blue colour is of a different appearance from what it is when the disease arises from the combination of venous and arterial blood. Disease of the right side is extremely rare, and many cases are detailed as such, which, in reality, are merely original formations, depending on the fact, not generally attended to, of the two ventricles, during the foetal state, being nearly of equal size and structure, which often continues through life without any very dangerous consequences. As to the mechanical idea of the blood being driven through the lungs with increased celerity, in cases of disease in the right side of the heart, the laws of the capillary system contradict it; for we find it impossible to inject, during life, those parts of the system that are most easily filled after death,—a clear proof of their independent action; and the great accumulation of black blood which is found in the lungs in cases of protracted disease, clearly proves, as demonstrated by Bichât, that the capillaries of that organ still retain sufficient energy to refuse its transmission to the left side of the heart, which, in these cases, is always found empty. These facts go to prove, that permanent blueness does not always depend on an original malformation of the heart, and that the altered colour, in cases of disease in the right side, is not produced by the mixture of arterial and venous blood. It has been proposed to call this symptom of blueness Cyanopathia, and there seems no objections to the term.
Before finishing these remarks, allow me to say a few words
regarding the circulation of the fœtus, and more particularly of the Eustachian valve.
Sabatier imagines, that the two currents of blood issuing from the venæ cavæ, cross each other, and do not mix; the stream from the superior cava goes into the right ventricle, and that from the inferior cava passes through the foramen ovale into the left auricle; and thus a different kind of blood circulates in the head and superior extremities, from that which goes down the aorta; and by this he explains the superior development of the head and upper extremities in the foetus. We are much surprised to find Bichât adopting this opinion in its greatest details, and giving Sabatier's figure of 8 as a correct view of the subject. Sabatier has endeavoured to establish this opinion from anatomical facts; and he assigns to the Eustachian valve the office of directing the current of blood from the vena cava inferior into the foramen ovale, and thus preventing the mixture.
The Eustachian valve, to fulfil this office, should have been placed at the posterior part of the vena cava, and of sufficient extent to cover the greater part of the diameter of the vena cava inferior, and also to have formed a sort of vault towards it, in order to make the blood of the superior cava glide over it. The posterior pillar of the foramen ovale seems quite unfit for that purpose, although Sabatier insists upon it. If, we examine the auricle attentively, we shall find no structure adequate to prevent the mixture of blood.
Le Gallois says, that the Eustachian valve, as it now stands, rather favours the mixture of blood than otherwise. The vestigium of the Eustachian valve, why does it not disappear after birth, like other parts whose functions have been performed? The lion, the cat, Guinea-pig, and dog, are destitute of a Eustachian valve. Another circumstance, in the right side of the heart, must favour also the mingling of the blood. There is a kind of cone formed at the mouth of the right ventricle, by the tricuspid valve, the base of which looks towards the auricle. At each contraction of the ventricle, the whole of the blood contained in the cone must be driven back into the auricle, the former being already full. It is from this fact that we explain the regularity in the circulation; for the capacity of the right ventricle having been proved in the adult to be larger than the left, if the former contracted on all the blood, the quantity discharged would be greatly in favour of the right side, and