On the first changes in the ova of the mammifera in consequence of impregnation, and on the mode of origin of the chorion / by Thomas Wharton Jones ; communicated by Richard Owen.

  • Thomas Wharton Jones
Date:
1837
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Licence: Public Domain Mark

Credit: On the first changes in the ova of the mammifera in consequence of impregnation, and on the mode of origin of the chorion / by Thomas Wharton Jones ; communicated by Richard Owen. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    side, quite transparent, except at its most projecting point, where there was a spot of blood. I perceived nothing peculiar in the ovum contained in this vesicle. I did not detect a germinal vesicle in it. Besides this large and prominent Graafian vesicle there were on the surface of the right ovary other five prominent vesicles filled with coagulated blood. At the most projecting point of each of these there was a small whitish mammillary elevation, within which was contained the ovum, surrounded by a transparent gelatinous sub- stance, the same as that described in the preceding observation; only it is to be re- marked, that in the Fallopian tubes this gelatinous looking substance had swelled out and acquired a greater diameter than it presented in the ovary. I did not detect a germinal vesicle in the ova forming the subject of this observation. In the left ovary I found only one vesicle, containing the coagulated blood and the ovum surrounded by the gelatinous looking envelope. Observation 3.—A Rabbit 48 hours after impregnation presented appearances much the same as the above. Is any trace of the gelatinous looking envelope of the ovum to be observed before impregnation? In the ova of the Rabbit, &c., before impregnation, the proligerous disc, in which the ovum is imbedded, is observed to be composed of a gelatinous substance interspersed with grains, but as yet there appears no distinctly circum- scribed envelope*. The gelatinous looking envelope of the ovum I have just described must not be confounded with the vitellary membrane of the ovum, which was fully considered in my former paper. The former appears to be analogous to the cortical membrane surrounding the ovum of the Ornithorhynchns paradoxus, &c. while still in the ovary, described by Mr. OwEN-f-. That it, and not the vitellary membrane, as I formerly imagined, forms the chorion, will be made evident by the following observations. I would, however, premise some remarks on the ova of the batrachian reptiles, in order to place in a more striking point of view the circumstances I am about to re- late in regard to the ova of the mammifera. Fig. 2. exhibits the ovum of the Frog magnified 2 diameters. It is composed of a yelk, black on its surface, and whitish inside. The yelk is surrounded by a vitellary membrane, thicker than that of the bird’s egg, but thinner in proportion than that of the ova of the mammifera. Outside the vitellary membrane is a gelatinous envelope, which is added in the oviduct, the two preceding parts being formed in the ovary. When the ova are laid the gelatinous envelope rapidly absorbs water, and swells out to great thickness. * Dr. Karl Krause of Gottingen, however, in a late Number of Muller’s Archiv., speaks as if the gela- tinous substance really formed a well defined envelope. From his observations on the ovum before impregna- tion ha has been led to form much the same opinion regarding the origin of the chorion as is recorded in this memoir. -j- Philosophical Transactions, 1834, p. 561.
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