1. Professor Boer, who fills the Chair of Zoology at Kœnigsberg, is a man of undoubted veracity, a keen and accurate observer, and has been engaged for many years in the investigation of that most interesting function—reproduction—in mammiferous animals. He made a great number of minute and extremely delicate experiments and microscopical observations on animals and the ovaria of women, which led him to the conclusions I have embodied in my propositions, and which he forwarded in a Latin epistle, entitled “De Ovi mammalium et hominis genesi”, to the Imperial Academy of St. Petersburgh, with a plate, carefully engraved, representing all the details above alluded to. These he afterwards, and within the last four years, enlarged upon very considerably in a subsequent publication.

2. If the reader can procure a placenta which has been thrown off immediately after the birth of the child, without any effort, and cleaning it of all coagula from off the surface which lay next to the uterus, by careful maceration and washing, he will afterwards introduce a small quill or pointed tube into one of the arteries of the navel-string, and blow strongly into it, he will find that the air raises upon that surface, to various degrees of puffiness, a very delicate pellicular covering, through which none of the air can escape, unless through an accidental laceration. I have often made the experiment, which I used to relate to my class in my lectures on midwifery many years ago. Lauth, of Strasburgh, has stated the same thing; so had Ruysch long since, and others, proving at once that there is not a direct communication with the mother from the fœtus.

3. It has hitherto been supposed, and Dr. Hunter first gave rise to the opinion, that on reaching the uterine orifice of the tube, the ovulum found an obstacle in the presence of the inner lamina of the decidua, which latter is said to be projected across that orifice. This obstacle the ovulum overcomes, Dr. Hunter supposes, by pushing the said lamina forward, and following it close, so at last to make good an entrance into the womb, surrounded by this inner lamina of the decidua, which the ovulum compels to enlarge with its own gradual enlargement, until both fill the entire cavity of the uterus, and the inner lamina of the decidua comes in contact with itself. It is impossible to conceive a more improbable operation, or one more contrary to facts. Yet such is the notion formed by Hunter of an imaginary membrane, to which he has given the name of reflected decidua; and so enamoured was he of this notion, that he has not hesitated to portray in his large work on the gravid uterus a section of the womb at several weeks after conception, (again purely imaginary,) representing things as he supposes them to be in regard to that membrane! Hunter’s notion was gradually converted into an opinion, which most of his successors have repeated over and over again, out of respect for him, and without ever inquiring experimentally into the correctness of it. No one has advanced a single fact to prove it. There is no such a thing as a decidua reflexa. The improbability of such a process as has been imagined to account for its supposed existence, has been demonstrated very adroitly by Dr. Dewees, as skilful and clear-sighted an obstetrical writer, of the United States of America, as any that have appeared in Europe. (Comp. of Midwifery, 1824, page 66.) He there shews, that if we adopt Burn’s description of the decidua reflexa, given by that author in a tone of positiveness, as if Hunter’s notion was a mathematical proposition, either that membrane must have three, instead of two, laminæ, as admitted by them, or it must have even a fourth lamina, namely, one more than has ever been imagined by any body. But the truth of the non-existence of a membrane formed in the manner in which the reflexa is said to be formed, is proved by actual facts. A few will suffice. A specimen of an impregnated uterus marked 3468 C. Gallery, Coll. Surg. of London, exhibits distinctly a round ovum naturally suspended within the decidua, as a globe may be supposed to hang from some point of the inside of an oblong sack. Here the ovum has pushed no part of the uterine decidua forward. The ovum has only its natural involucra, and there is a large space between them and the deciduous lining of the womb. In Dr. Agar’s case, alluded to before, in the Museum of the R. C. of Physicians, (impregnated uterus 2½ months,) no decidua reflexa is seen. Specimen 73, in Sir Charles Clarke’s collection, exhibits an ovulum which has already penetrated about an inch into the cavity of the uterine decidua, without pushing any part of it forward. Specimen 75 in the same collection is another illustration of the same fact. In good truth, the existence of the decidua reflexa is disproved by facts, and is moreover rendered inconceivable and inexplicable by the very account and explanation given by those who contend for that existence. It is now scarcely admitted by one out of ten Continental anatomists.

There is another physiological fact which we have overlooked—it is this: That the uterine decidua is always pervious at the uterine orifices of the fallopian tubes, as well as over the internal orifice of the cervix uteri. The error thus signalized has arisen from not knowing that the ovulum comes from the ovarium with a cortical membrane over the shaggy chorion. It is curious to see how, even among some of the most skilful of the modern physiologists, their ignorance of the existence of a cortex ovi has misled them in their respective descriptions of the decidua or uterine lining. Carus, for example, has asserted, that the decidua uteri had an opening over the internal orifice of its cervix. Velpeau and Breschet have denied this to be the fact, and consider the decidua to be a complete sac, to which they have ascribed the functions of a serous membrane. Professor Heusinger confirms the opinion of the two French authors, but denies that the decidua is a serous membrane. The truth lies between: Carus described the real decidua, which has three apertures; while Breschet, Velpeau, and Heusinger evidently refer to the cortex ovi which has no aperture whatever, when the ovulum enters the cavity of the womb. Well might Meckel exclaim, “il n’est pas très facile d’expliquer le mode de formation de la caduque reflechie.” (See specimen 73, 75, 76, 87, Museum of Sir Charles Clarke.)

4. It is impossible to desire a stronger or a more beautiful illustration of the modern theory of fecundation, than we find in the preparation here alluded to. It is the impregnated uterus (between two and three months) of a female who died of hydrophobia. Both the ovaria are laid open. In the left there are no appearances, beyond the Vesiculæ Graafianæ hardened by the alcohol: but in the right, namely, the ovarium of that side on which it is supposed that the fecundated Ovulum entered the womb, (from the circumstance of the placenta being implanted in that quarter,) we find not only a scar still red on the surface of the ovarium, but corresponding with it, and beneath it, in the thickness of the ovarium, a large shallow depression or hollow from which the Ovulum had escaped, and which is beginning to fill with the substance that is to constitute the corpus luteum destined to stop up the gap in the ovarium.

5. Meckel, with many others, entertain still the opinion that the corpus luteum precedes fecundation—but instead of supposing with Sir E. Home that it generates an Ovulum, the physiologist of Halle imagines that, like a testis, it serves to secrete a generating liquor—the semen feminæ. This theory is demolished by Boer’s, Plagge’s, and Messrs. Prevost and Dumas’s positive observations.

6. This disparity has not been noticed before by writers. Like many other circumstances, it militates, not a little, against the theory of the decidua reflexa.

7. Dr. Pockels calls this the Decidua—but in good truth it is the Cortex Ovi—for this good reason, that at so early a period, and even as late as the end of the first six weeks, the Decidua is many times larger in capacity than the ovulum, and is never globular like the latter. Besides, when Ovula of such early periods are thrown out, the decidua remains behind, and is ejected in its triangular shape, a little while, and sometimes even a day, after. In other respects, Dr. Pockels confirms Boer’s more precise description of the “Structure of the Ovum.”

8. The whole of the English physiologists, writers on midwifery, and lecturers, whether ancient or modern, are entirely silent on this important stage of embryonic life. They have talked rather loosely on the subject without the species of life which he must suppose the embryo to enjoy. He tells us, that even at the end of three weeks the Ovum is not found in the uterus, but how it exists during that period, wherever it may be, he has not even alluded to a single reference to facts or anatomical remarks of their own. Burns, in his work on abortion, never once alludes to

9. See a very interesting paper on the Structure of the Human Placenta, by T. Radford, Surgeon, &c. Manchester, 1832.

10. I shall submit to the Profession these curious and interesting experiments very shortly.

11. Autenrieth, in his “Supplementa ad Historiam Embryonis Humani”, has given the dimensions of the embryo and fœtus from a week to the 126th day of growth, with a description of the several parts as they appear at each period. From these he has drawn several conclusions respecting the growth of the human fœtus which have been generally adopted. Soemmering, in his “Icones Embryonum Humanorum,” has also given the dimensions of the human fœtus, from the earliest period he has seen it to its full maturity, with plates.

12. “Caput nutans per omne tempus quo in Ovo continetur.” And again,—“Quò junior embryo, eo major est volumen capitis.” (Soemmering.)

13. This doctrine has been controverted by two more recent experimentalists, Prevost and Dumas, as far as the chick is concerned. They assert that the rudiments of the spinal marrow appear before any other important organ.

14. In describing the figures in Plate I. under the head of “remarks” it is to be understood that by the expression of “the mossy vessels discharge their blood” is meant that they present themselves, immediately after the expulsion of the Ovulum, with very feeble tokens of the presence of blood at that early period of gestation.

15. The consideration of the development of the human embryo in its minutest parts, progressively watched and carefully examined and described, as those parts appear in succession, appertains to transcendant physiology, and would be out of place in these Prolegomena to a work which is intended to supply my brethren with practical information, obstetrical as well as medico-forensic. It is sufficient for my purpose to mention (as I have endeavoured to do) the forms which the fœtus presents, its different sizes, and the weights which correspond with those forms. To those of my readers who take an interest in embryogenesy, I recommend the careful perusal of the various continental modern authors repeatedly named in these Prolegomena. Unfortunately, since Hunter and Home, there has not been a single British practical and experimental physiologist who has investigated this subject either originally or otherwise. This fact, not at all flattering to us, is no where placed in so strong a light as in Breschet’s very erudite and classical memoirs, entitled “Etudes anatomiques, physiologiques et pathologiques de l’Oeuf duns l’Espèce humaine” which that indefatigable inquirer has enumerated and analyzed every statement and experiment made on that subject by upwards of thirty physiologists, down to the present day; among whom there is not, since Hunter and Home, a single English name besides that of Dr. Burns, recorded.

16. See Journal Complementaire, Vol. 6. p. 375.

17. I possess a placenta exhibiting these appearances (78, 79) in so distinct and beautiful a manner, that it would be a violation of truth and sincerity, or a sure sign of ignorance, to state that they do not properly resemble those which are observed in the Chorion of some of the mammalia. Those are cotyledons. So are these. I shewed the preparation to Dr. Hugh Ley. He was delighted with it, and instantly admitted the similarity in question.

18. Observations relatives à la Géneration. Par F. Lallemand. Paris, 1818.

19. Precis Elementaire de Physiologie, 2d edit. Paris, 1825.

20. Dr. Hunter on the Placenta. In Gravid Uterus, page 43, 9th edit. 1794.

21. A complete ovum, with the investing cortical membrane, and the entire decidua expelled nine weeks and three days after the last regular menstruation, in the case of a lady recently married, whom I attended (March, 1833), has afforded me ample opportunity of verifying the above and most of the previous propositions, through a careful dissection of the parts under water, and the use of the microscope.

22. MS. Lectures of Dr. Hunter, taken by John Sheldon, 2 Vol., formerly in the possession of Joshua Brooks, Esq. and now before me (Vol. II. page 485).

23. Communicated to the Philomatic Society of Paris, 1830.

24. Memoires de la Societé de Physique de Genève, T. IV. part 1.

25. American Journal of the Medical Sciences, Nov. 1829.

26. I am thus particular, because there is a second and even a third series of numbers in this collection, which are differently marked on the preparations and in the MS. lists, although belonging to the same specimens. This confusion which has crept in, in spite of Mr. Clift’s vigilance and endeavours to prevent it, will disappear as soon as that skilful naturalist shall have been able to complete the laborious task of making a catalogue raisonné, of the museum.