[17] 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 objections 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 frequently seen, and shall delay its minute consideration until we come to the description of the fœtus 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.
[18] Siebold’s Journal für Geburtshülfe, vol. xiv. heft. 3. 1835.
[19] On the Signs and Symptoms of Pregnancy, p. 133.: by W. F. Montgomery, M. D. In a note to the above quotation, the learned author very properly calls them decidual cotyledons, “for to that name their form, as well as their situation, appears strictly to entitle them: but from having, on more than one occasion, observed within their cavity a milky or chylous fluid, I am disposed to consider them reservoirs for nutrient fluids, separated from the maternal blood, to be thence absorbed for the support and development of the ovum. This view seems strengthened when we consider that, at the early periods of gestation, the ovum derives its support by imbibition, through the connexion existing between the decidua and the villous processes covering the outer surface of the chorion.”
[20] Observations by Dr. Baillie, in the posthumous work of Dr. W. Hunter, on the Anatomy of the Gravid Uterus.
[21] Observations on Certain Parts of the Animal Economy, p. 134.
[22] It has lately been supposed that the irregular nodules of wax in the Hunterian preparations were merely the result of extravasation, a rather hazardous conclusion against the authority of such men as the Hunters. Mr. J. Hunter has, however, expressly met this objection in the following observation:—“this substance of the placenta, now filled with injection, had nothing of a vascular appearance, or that of extravasation; but had a regularity in its form which showed it to be a natural cellular structure, fitted to be a reservoir for blood.” (Observations on Certain Parts of the Animal Economy, p. 129.)
[23] In offering these observations on the placenta, we have purposely quoted, wherever it was possible, from the admirable essays of the Hunter’s, on this subject. These works, more especially that of Dr. W. Hunter, are becoming too scarce to be easily attained by the student; and yet it is more peculiarly important to this class of our readers, that they should not only be aware how much we are indebted to these illustrious men for what we know upon the subject; but also that they should be as familiar as possible with their very words and expressions. The essays in question are master-pieces of original observation and correct description, and we may safely assert, that the one by Dr. Hunter is so complete, as to leave us little or nothing more to be wished for on this subject. With such feelings we cannot conceal our surprise, to find that an author like Dr. Burns should have passed over the whole subject of the placenta without once alluding to the name of Hunter; this omission is the more marked in the last editions of his work, where he has furnished the reader with copious references, &c. in the notes. One would have thought that Dr. Burns would have felt pride in acknowledging the merits of his distinguished countrymen.
[24] We said, “one of the earliest changes.” Mr. Jones considers that “the breaking up of the surface of the yelk into crystalline forms,” is the first change which he has observed.
[25] Allen Thomson on the Development of the Vascular System in the Fœtus of Vertebrated Animal. (Edin. New Philosop. Journ. Oct. 1830.)
[26] Pander. Beiträge zur Entwickelungs-gesechichte des Hünchens im Eie. Würzburg, 1817.