NATURAL HISTORY. Account of the Dissection of a Human Fetus, in which the Circulation of the Blood was carried on without a Heart. By Mr. B. C. Brodie. [From the Phi. losophical Transactions of the Royal Society of London, for 1809.] A N opportunity lately occurred to me of examining a human fetus, in which the heart was wanting, and the circulation of the blood was carried on by the action of the vessels only. There have been some other instances of this remarkable deviation from the natural structure; but in that to which I allude, the growth of the child had been natural, and it dif. fered much less from the natural formation than in any of those which are on record, and I have therefore been induced to draw up the following account of it. A woman was delivered of twins in the beginning of the seventh month of pregnancy. There was a placenta with two umbilical chords, which had their origin about three inches distant from each other. The placenta was not preserved, but Mr. Adams, who attended the mother in her lying in, observed nothing unusual in its appearance. Both fœtuses were born dead. They were nearly of the same size. One of them in no respect differed from the ordinary formation; the other had an unusual appearance, and Mr. Adams thought it deserving of examina. tion. Through Dr. Hooper it was put into my hands for this pur pose. The fœtus measured thirteen inches from the summit of the cranium to the feet. The thorax and abdomen were surrounded by a large shapeless mass, which conccaled the form of the whole upper part of the body. This mass proved to be the integuments co. vering the posterior part of the neck and thorax, distended with a watery fluid, about three pints in quantity, contained in two cysts, lined by a smooth membrane. When the fluid was evacuated, and the cysts allowed to collapse, the foetus had nearly the natural form. Its extremities had nearly the usual appearance, except that on the right hand there was no thumb; on the left hand there was no thumb also, and only a single finger. There were three toes on the right foot, and four toes on the left foot. The external nostrils consisted only of two folds of 3 E 3 skin, skin, under each of which was the orifice of an internal nostril, but pervious only for about half an inch. There was a hare-lip, and a cleft in the bony palate, extending one third of an inch backwards. On dissection the cranium was found somewhat compressed by the fluid contained in the cyst behind it. The brain itself was too putrid for accurate examination, but it was of nearly the natural size, and nothing unusual was observed in it. The membranes had the natural appearance, and the nerves appeared to go off from the brain and spinal marrow nearly as usual. In the thorax there was по heart, thymus gland, or pleura, The trachea was situated imme. diately behind the sternum. It had its natural appearance, and divided as usual into the two bronchia. The latter terminated in the lungs, which consisted of two rounded bodies, not more than one third of an inch in diameter, having a smooth external surface, and composed internally of a dense cel. lular substance. The esophagus had the usual situation, but it terminated in a cul-desac at the lower part of the thorax. The rest of the thorax was filled with a dense cellular substance; and in place of the diaphragm, there was a membranous septum between it and the cavity of the abdomen. In the abdomen, the stomach had no cardiac orifice. The intestine was attached to the mesentery in the usual way; but it was proportionably shorter than natural. There was an imperfect cœcum, but the colon was not distin. guished by any difference of struc ture or appearance from the rest of the intestine. The rectum had its usual situation in the pelvis. The spleen and renal capsules were small; the kidneys, bladder, penis, and testicles, had the usual appear. ance. The abdomen was lined by peritoneum, but there was no omentum. The liver and gall. bladder were wanting. As there was no heart, it became an object of importance to ascer. tain the exact nature of the circu lation for this purpose the bloodvessels were traced with atter. tion. The umbilical chord consisted of two vessels only: one of these was larger than the other, and its coats resembled those of a vein, while those of the smaller vessel were thick and elastic, like those of an artery. Both of these vessels entered the navel of the child. The artery passed to the left groin by the side of the urachus, occupying the usual situation of the left um. bilical artery. Here it gave off the external and internal iliac arteries of the left side, and was then costinued upwards on the fore part of the spine forming the aorta. From the aorta arose the common trunk of the right iliac artery, and the branches to the viscera and pa. rietes of the thorax and abdomen. At the upper part of the thorax, it sent off the two subclavian, and afterwards divided into the two carotid arteries, without forming an arch. The veins corresponding to these arteries terminated in the vena cava, which was situated on the anterior part of the spine be. fore the aorta, and passed down. wards before the right kidney to the right groin. Here it became reflected upwards by the side of the urachus to the navel, and was continued into the larger vessel or vein of the chord. It appears, therefore, that in this fœtus, not only the heart was wanting, but there was no communication of any kind between the trunks of the venous and arterial systems, as in the natural fee. tus, where there is a heart. The only communication between the two sets of vessels, was by means of the capillary branches anasto. mosing as usual in the fœtus, and in the placenta. The blood must have been propelled from the placenta to the child, through the artery of the chord, and must have been returned to the placenta by means of the vein, so that the placenta must have been at once the source and the termination of the circulation, and the blood must have been propelled by the action of the vessels only. It is to be understood, that the circulation in the foetus receives no propelling power from the ac. tion of the heart and arteries of the mother. This, although perfectly known to anatomists, it is proper to mention, as it may not be equally known to all the menbers of this society. It appears extraordinary, that under these circumstances, not. withstanding the circulation through the placenta must have been more languid than is natural, that organ, should nevertheless have been capable of exercising its proper func. tions, so as to produce those changes on the blood, which are necessary for the maintenance of fœtal life. This may be explained by considering that in the natural foetus the umbilical arteries are branches of the general arterial system, and only a portion of the blood of the child is sent to the placenta, whereas in the foetus which I have described, the trunk of the vena cava was continued into the vein of the chord, and the whole of the venous blood circu lated through the placenta, and was exposed to the influence of the arterial blood of the mother. But the most interesting circumstance which we learn from this examination is, that the circu lation not only can be carried on without a heart, but that a child so circumstanced can be maintained in its growth, so as to attain the same size as a fœtus, which is possessed of that organ. This fact is contrary to what prior experience has led us to expect, as will appear from the following abstract of the authenticated cases of this species of malformation, which we find on record. A monster, in which there was no heart, is described by M. Mery*. There were twins, one of which was well formed, and of the usual size of a six-months' child: the size of the other was not mentioned, so that no comparison could be made between them. In the latter, the head, neck, and other extremities were wanting There were no vestiges of a brain, nor was there any liver. The dissection of the blood-vessels does not appear to have been very accurately made, but, from the gene. ral account, I should suppose that the circulation did not materially differ from that of the fœtus which I have described. Another instance of this kind is • Histoire de l'Academie Royale des Sciences, 1720. 3 E 4 de described by M. Winslow *. This was also a twin, only seven inches in length. The age and size of the other child are not mentioned. In this instance there was no head, nor any vestige of brain. There were no lungs, liver, stomach, nor spleen, and only a small portion of intestine. The arterial system is described as being complete, communicating with the placenta by the umbilical vein opening into the aorta, and the umbilical arteries arising nearly as usual. In this instance there was a circle of vessels formed by the arteries only, for M. Winslow expressly states, that there were no veins; and however extraordinary this may appear, we cannot be otherwise than cautious in denying an observation made by an anatomist so remarkable for his extreme accu. racy and minuteness. Dr. Le Cat, of Rouen, states another case of twinst born at the end of the ninth month of pregnancy. One of them was a well. formed child, of the usual size, but the other was only twelve inches and a half in length. The head of the latter was very imperfect, and there was only a very minute por. tion of brain. The heart, lungs, liver, stomach, and spleen, were entirely wanting, and there was only a small portion of intestine. The arterial system was perfect; the umbilical vein terminated in the aorta, and the umbilical arteries had their origin from the internal iliac, as usual. There is, however, an obscurity in the account of the circulation, as it is stated that there were veins, but they were not traced, nor was any commxaica. tion made out between them and the arteries, or the vessels of the chord. Dr. Clarket has given an ac. count of a case, in which a wo. man, after a natural labour, was delivered of a healthy child, and also of a substance covered by common integuments, of an oval form, four inches in length, and having a separate navel-string and placenta. In this substance there was one os innominatum, with a femur, tibia, and fibula. There were neither brain nor nerves; not were there any viscera, except a small portion of intestine. The umbilical chord consisted of two vessels, an artery and a vein, both of which ramified in this substance and in the placenta. In Dr. Hunter's anatomical col. lection, there are two specimens of monsters born without hearts. In both of them the whole upper part of the body was wanting; and in neither was the exact nature of the circulation ascertained. In each of the instances whichl have quoted, not only the heart was wanting, but the foetus in other respects was so imperfect, that it could not be considered as any thing more than a mola, or an ir regularly-formed living mass con. nected with the placenta. In par ticular, in all of them the brain, which may with justice be consi dered as affording the best distint. tion between a mola and a fœtus, was wanting; whereas in that which forms the subject of the * Histoire de l'Academie Royale des Sciences, 1740.+ Phil. Trans. for 1707. Phil. Trans, for 1793. present present paper, the brain was nearly as large as usual, and in other respects the foetus varied much less from the natural structure, than in any former instance.. In the cases already on record, we have seen, that wherever the size of the monster was mentioned, it was much smaller than a natural foetus. This would have led to the supposition, that a cireulation, which was carried on by the action of the vessels only, was incapable of maintaining the natural growth of a child, had it not been found that the foetus, which I have described, though the heart was wanting, was fully equal in size to a fœtus of the same age, which was possessed of that organ. It may be observed, that in all these cases, in which the heart was wanting, the liver was wanting also. It is probable that the action of the vessels only, without the assistance of the heart, would have been insufficient to propel the blood through the circulation of the liver, which is so extensive in the natural fœtus. On the Origin and Formation of Roots. By T. A. Knight, Esq. F. R.S. [From the same.] IN a former communication I have given an account of some experiments, which induced me to conclude that the buds of trees invariably spring from their albur num, to which they are always connected by central vessels of Phil. Trans, 1805. greater or less length; and in the course of much subsequent expe rience, I have not found any rea son to change the opinion that I have there given *. The object of the present communication is to show, that the roots of trees are always generated by the vessels which pass from the cotyledons of the seed, and from the leaves, through the leave-stalks and the bark, and that they never, under any circumstances, spring imme diately from the alburnun The organ, which naturalists have called the radicle in the seed, is generally supposed to be analo gous to the root of the plant, and to become a perfect root during germination; and I do not know that this opinion has ever been con troverted, though I believe that, when closely investigated, it will prove to be founded in error. A root, in all cases with which I am acquainted, elongates only by new parts which are successively added to its apex or point, and never, like the stem or branch, by the extension of parts previously organized; and I have endeavour. ed to shew, in a former memoir, that owing to this difference in the mode of the growth of the root and lengthened plumule of ger minating seeds, the one must ever be obedient to gravitation, and point towards the centre of the earth, whilst the other must take the opposite direction t. But the radicle of germinating seeds elongates by the extension of parts previously organized, and in a great number of cases, which must be familiar to every person's observa, + Phil. Trans, 1806. |