1847)

Placental Cells do not exist.

19

itself in, is carried before it into the cavity of the vein, and that this projected part (of the lining membrane) is carried over the tuft and each of its individual fringes; or, in other words, that each tuft projecting into the vein fills up the pushed-forward, inner venous membrane, and that in this manner this latter is carried over the fringes of the tufts."

After again insisting upon these relations of the maternal and foetal portions of the placenta, and precisely defining the whole structure, Weber gives the following summary of the modus operandi of this complex organization.

"The physiological actions of the human placenta appear then to consist in this-that the large stream of the embryonic blood is so conducted over the still larger current of the maternal blood, as that every blood-corpuscle of the fœtus, whilst it circulates through the placenta, comes into a very intimate but indirect contact with the blood of the mother for some considerable time. This is effected in consequence of the blood-stream of the embryo being so divided by traversing an infinite number of minute canals, that only a single series of corpuscles can pass along, whilst the maternal stream flows in very wide thin-walled passages, into which the tufts of the foetal placenta project, and are bathed by the maternal blood flowing over them. Now, since the blood of the fœtus flows through the fine, hair-like extremities of these tufts, it may be presumed that it can attract through the extremely thin and moist parietes of the fine and elongated capillary vessels, certain substances contained in the maternal blood; and, on the other hand, that the maternal current of blood can doubtless also effect, through the attenuated parietes of its containing canals, an attraction or absorption of certain substances existing in the fœtal blood.-(E. H. Weber's edition of Hildebrant's Hand. der Anat. Band, IV. p. 496-499.)

The researches we have thus cursorily explained, illustrate so perfectly and minutely the intimate texture of the placenta, that, combined with the equally important and original observations of the same author upon the uterine glands and the arrangement of the capillaries of the umbilical blood-vessels, they have left little more to be determined. They entirely explode the Hunterian doctrine of the maternal blood being extravasated or deposited by the curling arteries in the so-called "cells" of the placenta ; they reveal the exact disposition of the chorion-tufts and of their contained blood-vessels; they do away with all the vague ideas of vessels with open mouths; they disprove the agency of lymphatics; and, finally, they explain the physiological phenomena connected with the introduction of nutritious matter into the system of the embryo. The term "cells of the placenta," indicating thereby extra-vascular cavities, has been so frequently used in descriptions of this organ, and in this country even of late years by writers who are looked up to as high authorities in this branch of medical science, that it is desirable distinctly to state that no such "cells" exist. It may be affirmed as a fixed law of the circulation, that the blood never quits its containing channels en masse; that is to say, it is never extravasated. The principal cause of the errors which have so constantly prevailed upon this point among writers unacquainted with microscopic and structural anatomy, are firstly, that where blood-vessels, and especially the veins, are either removed from external pressure, as in the case of the bones, or are connected with functions demanding a ready passage to and from the contained blood, their parietes become extremely attenuated, and are therefore often overlooked; and, secondly, that when such vessels are

artificially injected, especially when this is rudely done, as is usually the case, their delicate membranes are torn through, and a deceptive appearance of cells is thus produced.

The later inquiries of Dr. Reid and Mr. Goodsir have confirmed the account of Weber, and have thrown additional light on the minute relations of the maternal and fœtal vessels and membranes. The observations of the latter gentleman are particularly interesting; and although several of his physiological inferences are to a great extent speculative, his paper should be carefully considered by all who desire to become thoroughly acquainted with the subject to which it relates.-See Med. Chir. Rev., July 1845.

As additional evidence of the correctness of Professor Weber's views, is still desirable, we may take this opportunity of stating that, we have lately had an opportunity of examining two gravid uteri of about the fifth and sixth month respectively, and in which the placentæ having been previously minutely injected both from the maternal and fœtal vessels, were favourably displayed. We were thus enabled distinctly to follow the uterine veins into the placenta, the passage taking place opposite to the interlobular spaces. Where quitting the fibrous coat of the uterus just at the point of entrance into the placenta, the walls of these enlarged veins become extremely thin and most liable to laceration, a circumstance which is doubtless a principal cause of the uncertainty that has prevailed upon this disposition. Just where the uterine veins had got to the placenta, tufts of the chorion were seen projecting into their cavities, as described by Weber and Reid; but no tufts were in either case seen pushing into the veins of the walls of the uterus, a disposition noticed by the latter observer. An injection of size having been employed, the curling uterine arteries could not be traced very satisfactorily into the placenta; but it was yet evident that at several points this transit took place. The maternal vessels having been filled in one of the specimens with red and the foetal vessels with a yellow injection, the two orders of tubes could be distinctly followed; and in this way it was found, what other observers have noticed, that the uterine vessels penetrated completely to the fœtal surface of the placenta, and the umbilical vessels, as above stated, as far as to where the placenta came in contact with the fibrous coat of the uterus. A clean vertical section through the fundus uteri, displayed very beautifully the remarkable mechanism of the uterine veins for preventing hæmorrhage on the separation of the placenta; the free inter-communications of these vessels being provided with valve-like processes of the fibrous substance of the uterus, produce the same effect as if each of the uterine veins had been divided into a numerous series of chambers provided with muscular, contractile valves, and thus capable of being completely closed. This disposition becomes more and more developed, as the veins approach the inner surface of the uterus, or the place where, in parturition, they are torn across; and it thus happens, as Professor Owen has so well described, that on the forcible contraction of the organ, subsequent to the separation of the placenta, the whole of this complex valvular apparatus comes into play, and, by compressing the enormously dilated and now ruptured veins, effectively guards against the fearful hæmorrhage which must otherwise have taken place. It is further evident, that although this interesting arrangement is sufficient to prevent the loss of blood when the

1847]

Circulation of the Placenta.

21

whole of it is called into action on the normal detachment of the placenta, that if a partial separation of this organ takes place in the course of gestation without delivery following, the uterus not contracting, profuse hæmorrhage must occur.

All this shows that the contraction of the uterus is the essential means employed by Nature to prevent the loss of blood on the separation of the placenta, so far as the uterine veins are concerned. The mode in which arterial hæmorrhage is guarded against, is not so well understood. The forcible contraction of the muscular uterine walls is doubtless one cause; and probably the remarkable coils described by the uterine arteries at the place of their entrance into the placenta, by inducing an elastic retraction after laceration, may, by aiding the other known means adopted by nature in the spontaneous suppression of hæmorrhage, be another influential circumstance, especially as regards vessels of the moderate magnitude of the "curling arteries."

The exact mode in which these last-named arteries end in the commeneing branches of the uterine veins implanted in the placenta, is not known; but it cannot be doubted there is a direct continuity between the two sets of vessels. It is also certain that the arrangement and character both of the uterine and umbilical blood-vessels are such as to retard, in a remarkable degree, the velocity of the circulation; in the former vessels, owing to the great magnitude of the veins or sinuses as they are called; and in the latter, in consequence of the very interesting disposition of the capillaries lodged within the tufts of the chorion, and so admirably described and defined by Professor E. H. Weber, and, independently, by Mr. Dalrymple. The principal peculiarity of these umbilical capillaries is their great number, in proportion to the stems with which they are connected; a disposition which has an influence in diminishing the rapidity of the blood's current, both by enlarging the aggregate space through which it flows in passing from the arteries into the capillaries, and also by increasing the amount of friction owing to the minute size of the individual channels. It will not be superfluous to state, that the mechanical arrangement of the uterine arteries penetrating the convex surface of the placenta, and of the umbilical arteries entering by the concave surface of that organ, both being very much coiled, especially the former, is such as must further concur in retarding the placental circulation.

The general result of all these elaborate arrangements is to allow time for that important reciprocal interchange of materials between the maternal and foetal blood, which has already been alluded to, and on which the nourishment of the fœtus depends.

The large divisions of the uterine sinuses lodged between the lobes of the placenta communicate together, as can be proved by tracing them and also by inflation; there is therefore a disposition which, independently of any other circumstances, would tend to cause hæmorrhage from the substance of the placenta in cases of partial separation of that organ.

We have inserted the title of Dr. Erdl's work at the head of this article, not with an intention of noticing it on the present occasion, but for the purpose of calling the attention of our readers to the fact of its publication. It consists of a numerous series of plates illustrative of the development of the chick and human embryo, with brief explanations; and although

we think that some of the drawings might have been more happily designed and executed, and that the descriptions should have been given in Latin as well as German, yet, upon the whole, it is a very useful work, and we therefore recommend it to our readers, and especially to medical societies, as a desirable addition for their libraries. It is, however, necessary to state that at present the first volume only, consisting of two parts, has been published; the whole work is to consist of two volumes, and will, there is no doubt, be speedily completed.

The objects of Dr. Erdl's publication will be gathered from the following extract. "Under this title (Die Entwickelung des Menschen, &c.), I present to students, to teachers, and to those who are devoted to scientific pursuits, a work which is designed to supply a defect of some moment in physiological literature. My object is to give, as accurately as possible, figures of the various stages of development of the human embryo and of its individual organs and tissues, accompanied by an explanatory text. But as in the human embryo many of the earliest processes cannot be detected, I have endeavoured to supply the deficiency by means of observations made on the hen's egg."-Prospectus.

We shall probably, on a future occasion, have an opportunity of briefly noticing the work of Dr. Erdl, in connexion with the subjects which it more especially is designed to illustrate, the development, namely, of the body, organs, and tissues of the embryo.

TRAITÉ ELÉMENTAIRE ET PRATIQUE DE PATHOLOGIE INTERNE. Par A. Grisolle, M.D.P., Médecin de l'Hôpital St. Antoine agrégé à la Faculté de Médecine. Deuxieme Edition, revue et augmentée.

AN ELEMENTARY AND PRACTICAL TREATISE ON INTERNAL PATHOLOGY. By A. Grisolle, M.D. P. Second Edition. In Two Vols. Octavo, pp. 1679.

A SYSTEMATIC Work on Internal Pathology, or, as we should call it in this country, on the practice of medicine, from the pen of a distinguished physician of one of the Parisian hospitals, and which is already before the public in a second edition, cannot fail to claim the attention of the British practitioner and medical student. But its importance becomes more apparent when it is known that the views which the author sets forth have been principally taken in the wards of La Charité, and from the practice of Professor Chomel, who may be justly regarded as one of the most eminent, eclectic, or Hippocratic physicians of the present day. In this respect the author has trodden in the footsteps of Professor Louis, and may be esteemed of the same medical school with him and Professor Andral.

It is the design of the work to exhibit the state of medicine at the present day, as it exists not in France only, but in the other countries of Europe, and in the United States. But, although the author has shewn a better acquaintance with English medical writers than is often to be found

1847]

Classification of Diseases.

23

amongst French physicians, it is evident that even he is imperfectly informed regarding the state of medicine in England.

In a systematic work like that of Dr. Grisolle the arrangement of the subject is a matter of no small importance. The author has adopted that which he calls a philosophical or nosological system, by which it is to be understood that his object is to bring together those diseases which are allied by the character and nature of the symptoms which they present, and which may therefore be supposed to require a parity of reasoning for their explanation, and analogous treatment for their cure. He prefers this to a pathological system, which might be founded either upon the classification of tissues, in which the particular derangements characteristic of different diseases occur, or upon the systems of organs subservient to the different functions of the body. There are advantages presented by each of these methods, but in the opinion of the author they are not equal to those of a nosological arrangement. The alphabetical order he rejects at once, condemning it as the worst that could be selected. In this opinion, if it is to be restricted to a comprehensive work for the use of the medical student, there is no one acquainted with the subject who will not readily concur. But in the application of the alphabetical method, as practically employed, it must be remembered that it is almost entirely restricted to large works of reference, such as the various Encyclopædias of medicine and surgery which are adapted to the use of those who are engaged in practice, or who may be already far advanced in the study of their profession. Each article in such works constitutes a monograph, in which the attention of the writer, as well as that of the reader, is concentrated upon the particular subject without his being necessarily obliged to consider what may be advanced in other parts of the extended work. In such a publication, the superiority of an alphabetical arrangement cannot be disputed.

The author observes with Requin, that Nosography must, in the present day at least, be neither exclusively organic, ætiological, nor symptomatic, but must assume a triple character. A mixed system must therefore be adopted to avoid mutilating the science, or leading it astray into hazardous hypotheses.

:

On this principle the following division into ten classes is employed :1. Fevers.

II. Diseases consisting in a fault in the proportion of blood.

III. Inflammations.

IV. Hæmorrhages.

V. Morbid secretions.

VI. The results of poisons.

VII. Diseases of nutrition.

VIII. Structural changes and accidental productions.

IX. Nervous diseases.

X. Diseases peculiar to certain organs or tissues.

We shall not attempt to criticise this classification, which the author does not pretend to be perfect. The number of authors who have already tried their hands on the construction of nosological systems sufficiently attest the difficulty of the task. These systems, which are necessarily more or less artificial, serve as the frame-work or skeleton to the body of