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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![an example of this occm s (Plate VII. figs. 121 A. to 123. hh\). Each of the concentric layers of which the germ consists, is so distinctly ciiciimscribed as to appear deli- cately membranous at its surface (par. 212.) ; or in otlier words, each concentric layer appears to be contained within a vesicle. Now here, as just stated, the inter- vening spaces are occupied by dark globules, subsequently foi-ming vesicles. 304. More particularly considered, the situation, and perhaps the place of origin of the dark globules in question, is in some instances on the outer surf ace of the inner vesicle or nucleus; of which Plate VIII. fig. 150. affords a remarkable example, in the lamina subsequently vascular-|~. The dark globules in the network Plate VIII. fig. 132, in every instance surround the nucleus-|~. The yelk-globules (vesicles) seem to arise on the outer surface of the germinal vesicle;{:'}-. In other instances the foundations of new vesicles arise as dark globules on the external surface of an outer vesicle. This is the case with the vesicles forming the villi of the chorion (par. 223.); and perhaps the isolated spots occurring in the Graafian vesicle may be mentioned as anotlier example 305. On the liquefaction of the membrane of a vesicle dark globules are some- times liberated. This takes place, for instance, whentlie membranous portion of the network (composed of vesicles, par. 201.) Plate VIII. fig. 132, disappears. (See Plate VII. fig. 120. Whether the dark globules which the latter figure shows to have been set free, are the foundations of new vesicles, I do not know; but in an ovum of about the same size the corresponding part presented vesicles in such quantity as to be pressed together into polyhedral figures, Plate VIII. fig. 150. From some observa- tions on the vesicles of which the incipient embryo is composed, I am disposed to think the dark globules exhibited in Plate VIII. fig. 149. (or a part of them) may have been liberated in the same manner. 306. In Plate VIII. fig. 143. is an ovum of twenty-three hours from the Fallopian tube. It was found with five others, and they were all lying very near together. These ova had penetrated about \ to \ wa. inch into that part of the tube where its calibre suddenly diminishes ; a part which when rolled between the fingers is found to resemble the vas deferens. In this ovum (fig. 143.) the chorion had not separated universal. In the formation of animal tissues, on the other hand, Schwann found this to he rarely the case. The ohservations, however, now referred to, of the origin of vesicles in vesicles, relate to a period anterior to the formation of even the elementary parts of tissues (nervous tubes, muscular fibres, 6iC.), and therefore are not necessarily opposed to those of Schwann. t See the Note to par. 293. X See my First Series, /. c, Plate V. figs. 14 and 16. It is interesting to find, as already stated, not only that \he formation, but also that the liquefaction of the yelk-globules (vesicles) begins around the germinal vehicle (Plate V. figs. 99 and 100.). § These isolated spots were described in my First Series (par. 59. Plate VIII. fig. 66.) as consisting of one of the peculiar granules [vesicles] of the Graafian vesicle, having a peripheral accumulation consisting of oil-like globules.](https://iiif.wellcomecollection.org/image/b2197214x_0062.jp2/full/800%2C/0/default.jpg)
