The vitality of the blood : proved by physiological experiment, and its application to veterinary pathology demonstrated / by J.S. Gamgee.

  • Gamgee, Sampson, 1828-1886.
Date:
[1849?]
Catalogue details

Licence: Public Domain Mark

Credit: The vitality of the blood : proved by physiological experiment, and its application to veterinary pathology demonstrated / by J.S. Gamgee. 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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    of cells, whose nuclei are the central vesicles previously alluded to. [See Fig. '2, PL 1.] The most external cells coalesce at the periphery of the yolk in a membranous layer, the vesicula blastodermica, or germinal membrane, which increases in thickness by the increment of cells developed in the interior of the vitellus. Soon after its appear- ance the germinal membrane divides into two strata : the outer or serous one is the basis of the osseous, muscular, and tegumentary structures, whereas from the inner or mucous layer the viscera originate. Between these strata numerous granules accumulate to produce the area vasculosa; and on the vesicula blastodermica the germinal area is discerned as a dark spot, composed of cells and granules, the central part of which, being clear and trans- parent, is named the ai-ea pellucida. In the last-mentioned space the first trace of the embryo, or nota primitiva, appears in form of a hollow groove, beneath which is laid the foundation of the vertebral column by a mass of cells, the chorda dorsahs. [See Fig. 3, PI. 1.] While the nota primitiva acquires a pear-shaped figure, the contiguous cells, ascending in convergent ridges, form the laminae dorsales ; these coalesce, converting the groove into a canal, which is perfectly closed, except at its anterior part, where three projecting vesicles represent the future cerebrum. The extreme ends of the embryo now become inverted, and the oblong blasto- derma gradually separates from the evolving intestinal tube as the umbilical vesicle. From each side of the dorsal laminae two la- minjc viscerales take a direction forwards and inwards, mutuallv aiding each other in forming the anterior walls of the trunk. Having thus briefly sketched the earlier stages of embryonic development, some of the more important points deserve further consideration. During the first twenty-four hours, from the first appearance of the nota primitiva, projections from the external layer of the germinal membrane form anteriorly the involucrura capitis, posteriorly the involucrum cauduse, and laterally the lami- nae laterales : these unite in a visible cicatrix over the lumbar region, enclosing the embryo in a complete sac, designated the amnion. From the caudal extremity of the embryo, the allantois first protrudes as a mass of cells. In carnivora this membrane extends t