Licence: Public Domain Mark
Credit: Researches in embryology. (Second series) / by Martin Barry. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![touching- each other, many being about -'-o' apart, and others as much as asunder. At the part from which fig. 142. was taken they were most numerous. The villous tufts are yellowish-brown in colour. The very first indication of the formation of villi seems to consist in a few dark globules existing scattered over the surface of the cho- rion. 224. The mode, the period, and the place of origin of the chorion, are subjects on which physiologists are not agreed. Von Baer'|~ appears to suppose his sphere creuse a paroi mince of the ovarian ovum to become the membrane corticale (chorion) of ova in the uterus, thougli he does not express himself with certainty on the subject. CosTE:|:and R. Wagner^ consider the thick and transparent membrane (/) of tiie ovum in the ovary to be identical with the membrane called the chorion in tlie uterus. PuRKiNJE II, Valentin^!, and Allen Thomson-f-f-, maintain that analogy is in favour of the supposition that the chorion originates in the oviduct. Krause|:|: conjectures that it may be formed after the discharge of the ovum from the ovary, out of the disc of granules (my tunica granulosa and retinacula) which surrounds the ovum in that organ. T. Wharton Jones formerly believed the vitellary membrane(y') to form the chorion, but now supposes that the gelatinous coat ['proligerous disc'] acquired by the ovum in the ovary, and more especially circumscribed and defined after impregnation, constitutes the only covering of the vesicular blastoderma after the giving way of the vitellary membrane; that this gelatinous-looking coat forms the chorion, &c. My own observations on this subject have been recorded in preceding- pages (pars. 172. 173. 221. 222.)||||. 225. More particularly, the following are the views of T. Wharton Jones as to the mode, period, and place of origin of the chorion. He says^^, In the ova of the Rabbit, &c. before impregnation, the proligerous disc [= my tunica granulosa and t Lettre, &c. Commentaire, pj). 39, 40, 55. Von Baer has since expressed the opinion that in some Mammals, the Hog and Sheep for instance, this membrane arises after the ovum has left the ovary, by the secreted albumen—through a coagulation of its surface—forming for itself an investing membrane. He con- siders that in the Dog, however, the outer membrane of the ovarian ovum continues the outer membrane of ova in the uterus. (Ueber Entwickelungsgeschichte der Thiere. Beobachtung und Reflexion. Zweiter TheiL pp. 185 to 188, 18.37.). I Embryog6nie Comparee, p. 80. § Beitriige, &c., p. 36. II Encyclopiidisches Worterbuch, Zehnter Band, p. 128. ^ Handbuch der Entwickelungsgeschichte des Menschen mit vergleichender Kiicksicht der Entwickelung der Siiugethiere und Vogel, p. 39. tt L. c, p. 453. It Muller's Archiv, 1837. Heft I. pp. 28, 29. L. c, pp. 339—342. 111! I have in two instances observed the chorion to make its appearance at the surface of the thick trans- parent membrane/ ( zona pellucida) in ova still in the ovary and apparently about to be absorbed. Mace- ration seems sometimes to produce a similar eifect. See figs, xviii. and xxii. in Bernhaedt's dissertation, Symbolae ad ovi mammalium hlstoriam ante prsegnationem, Wratislaviae, 1834; and Edinburgh Medical and Surgical Journal, No. 128, Plate i. fig. 3, 1836, in which the transparent space surrounding the ovum appears to me to represent the fluid (/' in my figures) imbibed by the chorion, the latter being perhaps hidden by the surrounding granules of the zona granulosa (my tunica granulosa). L. c, p. 340.](https://iiif.wellcomecollection.org/image/b2197214x_0041.jp2/full/800%2C/0/default.jpg)
