Volume 1

Researches in embryology. Ser. 1-2. / [M. Barry].

  • Barry, M. (Martin), 1802-1855
Date:
1839
Catalogue details

Licence: Public Domain Mark

Credit: Researches in embryology. Ser. 1-2. / [M. Barry]. Source: Wellcome Collection.

    23/60 (page 321)
    seen the membrana granulosa to pass above the discus proligerus. On the immature ovulum [ovum] of the Cow, on the contrary, I have recognised no more than a conti- nuous lamina, which I consider as the membrana granulosa. From all that has been said, I think I may conclude that the ovula [ova] of the Mammalia, those at least which are approaching maturity, are plunged into a couch, formed of a thick emi- nence, the cumulus, and of a flat disc, and that the latter may or may not be primi- tively isolated from the membrana granulosa; development predominating some- times on the part of the disc, sometimes on the part of the cumulus, examples of which are offered (respectively) by the Bitch and Cow'f-'.” See Plate VII. fig. 62. and Plate VIII. fig. 80. 63. This description appears to be accurate in a few particulars, but for the most part it does not accord with my observations. I have naturally felt some hesitation in stating this, not only from its being opposed to the opinion of so experienced and, generally speaking, so accurate an observer, but because those who have succeeded Baer in these researches appear to have adopted entirely his description of this struc- ture. In now offering a different account of it, I would express my belief that should this prove more accurate, it will have been rather due to my examination of the ovum when situated in the centre (as well as near the surface) of the Graafian vesicle, than to imperfect observation on the part of those eminent observers. But I must first describe a structure which, to my surprise, has not been hitherto observed, though visible in those situations in which the ovum has been usually examined. The Tunica granulosa. 64. On the rupture of a Graafian vesicle under the compressor, the ovum escapes, and with it a mass of the peculiar granules I have at some length described (8.). This mass of granules, as hitherto obtained, has presented the appearance of a lace- rated structure, and been regarded simply as a portion of the ‘‘disc” of Baer§. I find, however, that if the mass thus escaping be attentively examined, those granules that immediately surround the ovum appear to be in a state of denser aggregation than the rest, from which they are to be distinguished therefore by a circumscribing line. If the granules thus circumscribed be viewed at different distances, they are seen to invest the whole surface of the ovum, forming a tunic, which is perfectly spherical in form (Plate VI. figs. 42. to 47-g1.). I have frequently obtained the ovum invested by no other granules than those of this tunic; that is, this tunic has been freed from the other granules, which on the bursting of a Graafian vesicle generally escape adherent to it; the fact being, that all that properly belongs to the ovum of the mass of granules in which it is found imbedded in the Graafian vesicle is this + Commentaire, &c., p. 40. + Lettre, &c., figs. ix. and xii. of Baer. These figures I have introduced for the purpose of contrasting them with my own drawings. § This lacerated structure is the “ zona granulosa” of Bernhardt, Symbolae, &c., figs. i. vii. xviii. xxi. xxiii. See also (in the present memoir) Plate VIII. fig. 72. g1., which is taken from that author. MDCCCXXXVIII. 2 T