Note 3 — PROLEGOMENA.

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.)