A system of midwifery / by Edward Rigby.

  • Rigby, Edward, 1804-1860.
Date:
1851
Catalogue details

Licence: Public Domain Mark

Credit: A system of midwifery / by Edward Rigby. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    CHAPTER III. DEVELOPMENT OF THE OVUM. MEMBRANA DECIDUA. — CHORION.—AMNION. — PLACENTA.]—UMBILICAL CORD.—EM- BRYO.—FCETAL CIRCULATION. Memhrana decidua. The earliest trace of impregnation -which is to be observed in the cavity of the uterus, and even before the ovum has reached it, is the presence of a soft humid paste-Uke secretion, with which the cavity of the uterus is covered, and which is furnished by the secreting vessels of its lining membrane. This is the memhrana decidua of Hunter: properly speaking, it should be called the maternal membrane, in contra- distinction to the chorion and amnion, which, as belonging peculiarly to the foetus, are called the fcetal membranes.* Although at first in a semi-liquid state, it soon becomes firmer and more compact, assuming the character of a membrane: it appears to be nothing else than an effusion of coagulable lymph on the internal surface of the uterus, having scarcely a more firm consistence than curd of milk or co- agulum of blood. (Hunter, op. cit. p. 54.) Hence although much thicker than the other membranes, it is weaker; it is also much less transparent. It is not of an equal thickness, being considerably thicker in the neigh- bourhood of the placenta than elsewhere; inferiorly, and especially near the OS uteri, it becomes thinner: during the first weeks of pregnancy it is much thicker than afterwards, becoming gradually thinner as pregnancy advances, until it is not half a line in thickness. In the earlier months its external surface is rough and flocculent, but afterwards it becomes smoother as its inner surface was at an earlier period. It is much more loosely connected with the uterus during the first months of pregnancy than afterwards, and this is one reason why prema- ture expulsion of the ovum is more liable to take place at this period than during the middle and latter part of utero-gestation. It is more firmly attached to the uterus in the vicinity of the placenta than any where else, which is owing to the greater number of blood-vessels it re- • We are aware that the plan which we follow, in considering the development of the ovum, is very different to that usually adopted, and will probably be open to some objec- tions on the score of defective arrangement; but it must be remembered that this is a work intended for students, where complete and perfect arrangement must, to a certain extent, be sacrificed in order to place an acknowledged difficult and complicated subject in the clearest and most intelligible light. We have, therefore, preferred describing first the coverings of the ovum during those periods of pregnancy at which they are most fre- quently seen, and shall delay its minute consideration until we come to the description of the fcetus itself, the development of the one being so essentially connected with that of the other, as to render a separate description of them impossible. By this means the reader, by having the general details first brought under his notice, will be enabled to enter with more ease and advantage upon the consideration of those which are obscure and difficult.
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