of his own examinations of the gravid uterus at full period: "I now believe they all fully bear out Mr. Hunter's general view, viz: that the maternal blood is diffused, by means of the tortuous arteries, into the spongy cellular substance of the placenta, where it bathes the capillaries of the foetal circulation, and is returned by the oblique decidual adventitious sinuses and channels into the orifices of the uterine veins." (Vide Note in Hunter on the Animal Economy, p. 102.)

M. Flourens, Professor of Comparative Physiology at the Jardin des Plantes, says, in his Cours sur la Génération, p. 130, that the umbilical vessels of the mammifers, which everywhere pierce the chorion, in order to come at the internal surface of the womb, are called placentas. The placenta is an inherent characteristic of viviparous production. It cannot, therefore, exist in the oviparæ. Mr. F. divides the mammals into two great classes, one of which comprises man, the rodentia, and the carnivora; while in the other class are arranged the pachydermata, the solipedes, and the ruminantia. In the first class, he contends, there is a vascular inosculation of the mother's vessels with those of the ovum, whereas no trace of such vascular union can be detected in the second.

I have cited this distinguished physiologist in order to show his opinion; but I am far from advising the Student to adopt it upon his authority. His assertion that the placenta is a characteristic of viviparous production, is denied by high authority; and notwithstanding I am prompted to agree with him, I admit that the most careful research has never enabled me to discover the least trace of a placenta or cord in the early marsupial embryon, as I have stated in my paper on the Didelphis, in Amer. Phil. Trans.

Mr. Owen's assertion, in regard to these differences in the classes, is as follows: "Thus the placental intercommunication between the foetus and mother, in the human subject and quadrumana, is carried on by the contact of the foetal capillaries with maternal extravasated blood; while in the ruminants, the mare and the sow, it takes place by the apposition of capillaries to capillaries, and the two parts of the placenta, viz: foetal and maternal, can be separated. In the ferræ and rodentia, there appears to be an intermediate structure." (Loc. cit.)

Let the Student, while pondering on these propositions of Masters in our science observe that, though the separation of the placenta in child-birth is essentially hemorrhagic, and never so in the parturition of quadrupeds, which might lead to inferences in favor of different plans of union, yet organs of such vital importance in the economy of the genera are not likely to be modelled upon plans absolutely different in creatures so nearly allied in their great types. In all the mammi

fers, there is one type for the brain and nerves, one for the respiration, one for the circulation, one for the absorption, secretions, reproduction, &c., and there should, à fortiori, be but one for the great and indispensable branchio-absorptive apparatus of the foetus.

I have already said that being in Paris in the year 1845, I enjoyed an opportunity to examine some of Professor Coste's preparations of

Fig. 53.

Fig. 54.

the gravid womb, as well as the water-color drawings, and engravings of them, aud I now repeat that the engravings are most faithful representations of the facts exhibited to me.

Let us suppose Mr. Coste's views as to the real nature of what is called the decidua to be absolutely correct, and let us consider the annexed Fig. 53 as a representation of a gravid womb cut through transversely from top to bottom,

and containing an early ovum imbedded in one of the plice or sulci of the tubular membrane, then the ovulum, partly buried in one of the sulci of the plicated membrane, will sit on the basement tissue, which is the womb itself. If an ovulum should be thus caught, fixed and half buried between the rug, it might form its mesenteric attachment at the bottom of the fold, and, daily increasing in size, it might cause its decidua reflexa to grow thinner, until it should, at last, wholly disappear, as in Fig.

54. The segment of the ovum that looks inwards to the cavity of the uterus, pierces through the thin coating of decidua, as in the figure annexed, and I have seen such an example.

As some of our brethren appear to take interest in the researches and opinions of Dr. Ernest Henry Weber, of the University of Leipsic, it is proper for me to show the grounds on which that author rests his theory. He directs that a gravid womb having been opened by an incision should be carefully washed, and then laid in alcohol to become somewhat hardened by the spirit. When sufficiently firm, an orifice of one of the veins opened in the uterine substance by the cut, should be sought, and the vessel inflated by means of a blowpipe. The inflated vein is then to be slit up with the scissors, and its track followed by successively inflating it and slitting it up. In this way the course of the vein is followed into the substance of the placenta, a certain portion of which is found to have been distended with the air of the blowpipe, which escapes from openings in accidentally broken vessels. The walls of these veins are so thin as to evidently consist only of the thinnest polished inner membrane. In this way, by dissecting and inflating, canals are discovered that are not really veins, but a sort of vacuoles and passages betwixt the spongioles of the fœtal part of the placenta. Occasionally one finds a vein in which the spongioles or tufts are pressed against the side of the vein, so that the inner wall or tube of the vessel is roughened by the intrusion; but it is to be understood that the tuft does not enter into the vein itself through an aperture in its wall: it only drives the thin vein-wall before it, reflects it, and so, covers itself with a coating of this vein-wall.

Weber supposes that these umbilical tufts that thus thrust the veinwalls before them, are arches or loops of vessels which in this manner carry their flowing blood as it were into the very heart of the vein without mixing the fluids however; the current in the large vein being protected by its indented vessel, and that in the umbilical one being confined to its own tube, so that the poor, half oxygenated blood of the embryon flows onwards in its own channel, which is surrounded with the hot rich fluid of its mother.

Such is Dr. Weber's idea; a very pretty and pleasing one-which, however, I cannot adopt, because I can never believe that the mother has any lot or part in the confectioning of the placenta, and which, moreover, is not called for by any absolute necessity of the case, seeing that vast whales, horses, oxen, and other great animals are as readily developed in gestation as man is, without any such complex apparatus. There is one law of gravitation, and I as fully believe, there is but one law of connection betwixt the embryon and its mammiferous parent.

In the human placenta, and in those of certain quadrupeds, all the placental tufts are united into a single disk, cake, or placenta, as in

the adjoining Fig. 55, which shows the uterine surface, where the lobules of the placenta are seen divided by the lines of the septa. These lobules are very numerous: and if, instead of being assembled in one disk, they were disseminated over various parts of the womb, the analogy to the ruminant organ would be complete. Fig. 56 exhiFig. 55.

Fig. 56.

bits the foetal surface of the placenta. The umbilical cord, containing its two arteries and its vein, is seen reaching the placenta at its centre, and dividing its vessels into numerous branches, which radiate towards the circumference. In other animals, as the ruminants, the tufts are separated from each other and distributed to different parts of the whole chorion, so as to make a great number of placentas. In certain other genera, the tufts consist of zones, surrounding the oval ovum; or they are scattered everywhere, like a paste, over the entire superficies of the ovum.

To possess a gravid womb at term, and enjoy an opportunity to examine it leisurely, is to be what Noortwyck calls rarissimum hocce spolium mactus. Even in London, Professor Owen appears to have waited long before obtaining such a privilege; and Dr. William Hunter says, that "opportunities of depicting the human pregnant uterus at leisure, very rarely occur. Indeed, to most anatomists, if they have happened at all, it has been but once or twice in their whole lives." (Anat. ut. Hum. Grav.)

I have enjoyed but few such opportunities during a long course of business in a great city. Those I have had were as carefully improved as my means would admit; and as I must confide in my own, rather than in other men's senses, I find it impossible, under my own observations, to adopt the views of the Hunters, and I prefer the opinions of Seiler and of Velpeau. One ought not lightly to dissent from great authorities, nor is it without a sentiment of profound respect for the

Hunters, that I claim the privilege to see with my own eyes, in a matter so authoritatively determined by those great benefactors of Medicine.

In what is called Deliverance, the whole placenta comes off from the womb. Kiwisch doubts that this is the case, supposing that a portion only of the maternal part comes off with the foetal portion.

As a general rule, the placenta is separated from its place on the vault of the fundus, by the same pain that chases the buttock of the child into the vagina, and is completely extruded from the genital fissure in about ten minutes: sometimes it is expelled within twenty minutes after the commencement of a labor.

I have removed a great number of placentas without staining the hand with blood, or perceiving a drop upon the mass itself.

The placenta comes off with equal readiness at the third, fifth, or the ninth month, showing that no other action of the womb is required for its expulsion than shrinking of its muscular tissue, and that all times and stages are indifferent as to the facility.

I find in dissecting the gravid womb at full term, that the slightest traction suffices to remove the placenta from the surface where it had ever before enjoyed an undisturbed attachment; and that, too, very soon after death. I am convinced that the connection may be broken up even by puffs of air from the blowpipe; and that it is not more adherent than is the peel of a perfectly ripe orange to the fruit. Can it be that the womb may exfoliate its half of the placenta with such amazing facility, and that, too, in all the stages of pregnancy? Do these facts consist with the idea that arteries pass from the womb into the placenta? Are other arteries broken so easily? Has the womb its half of a placenta?

I shall subsequently mention the case of a lady who died here in June, 1848. In the post-mortem examination in presence of Dr. Yardley and Dr. Wallace, I detached the whole of the placenta from the womb, after the careful injection of the aorta made by Dr. Wallace, an expert anatomist, who had secured the external iliacs before throwing the injection into the trunk. Neither I, nor those gentlemen, upon the most minute and careful search, aided by good lenses, could verify the existence of even a single vessel passing from the womb to the placenta. Much of the injection was effused into the cellular meshes of the placenta. It was an infiltration of the material and not an injection, in the anatomical sense of the term. We arose from the dissection, equally and unanimously convinced that we had not seen a single vessel broken off or pulled out, in the slow, gentle, and most careful divulsion of the two surfaces, uterine and placental.