Volume 2

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.

    69/100 (page 365)
    which are disposed in layers (figs. 121 A. to 122 hV.). Layer after layer conies into view in the interior (each layer appearing as if invested by a delicate capsule), while those previously occupying that situation are pushed farther out. These changes may be called primitive^, for at a certain period no more layers make their appearance, and the cavity inclosed by the most central layer becomes enlarged. It is very in- teresting to observe, that before those primitive changes have reached their limit, a structure is produced (by the layers of vesicles in question) having the form of the central portion of the nervous system, including even the sinus rhomboidalis of the spinal cord:]:. It is also interesting to find that the foundation of the vascular system is a part of the primordial germ (par. 216.). The nature of the alterations which the germ undergoes immediately after the termination of the primitive changes now re- ferred to, I do not know, not having carried my investigations beyond that period. It is probable that they consist chiefly in the formation of new vesicles. The object represented in figs. 125 and 126.—met with incidentally—was in a much more ad- vanced state as to form, and exhibited an incipient division into further forms (par. 218.); yet it presented no trace of separation into tissues. The origin of tissues, then, is subordinate to a division into forms. This may serve to elucidate the fact, that parts in different animals, having a general resemblance in form, are sometimes the seat of very different functions. And if the primordial germs of organized beings in general resemble one another in appearance, as much as, from my observations, it appears that they do in some instances very remote from one another, it is not surprising that there exist resemblances in the subsequent forms of beings more nearly allied. I refer, for example, to a curious resemblance between the mammiferous germ with its vesicle—as exhibited in Plate VI. fig. 113.—and the “cytoblast” and spore of a cryp- togamous plant (Rhizina Icevigata),—as figured by Schleiden in his paper on vege- table structure§. This observation will perhaps be considered as not undeserving of notice in connexion with the subject of analogies in the fundamental structure of organized beings. We find also, that there is a period in the formation of the Mammal —and therefore, it may be presumed, of Man himself—when the immediate founda- tion of the new being is contained within a simple cell,” vesicle, or sac. Method of obtaining the minutest Ova in the Uterus and Fallopian Tube; and. a mode of preserving them while under examination. 313. The almost entire absence heretofore of observations on the smallest ova in the oviduct of the Mammalia, may be attributed to the difficulty experienced by ob- t The separation of the germ into a central and a peripheral portion being the first of these primitive % I apprehend it would be an error to suppose that the fluid contained within a tube is the first appearance of the central portion of the nervous system. Its original foundation seems to be present from the first; and its form, as above stated, is seen before that of any other part. The object represented in Plate VII. figs. 125 and 126.—and more particularly its inner part—I am disposed to think consisted chiefly of the foundation of the central portion of the nervous system. § L. c.. Tab. III. fig. 11.