File:Bryce1908 fig03.jpg

Figure 3. Drawing of a reconstruction wax model of the Blastocyst

The outer darker layer is the cyto-trophoblast ; the inner lighter, the mesoblast represented as if solid. The irregular cavity is the retraction cavity in the mesoblast. It contains two vesicles ; the larger is the torn and collapsed amnio-embryonic vesicle, the smaller is the entodermic vesicle.

The model was constructed by building up wax plates to represent what was really a cast of the cavity of the blastocyst, with a space in ita centre containing the vesicles. The model was then cut across so as to present to view the portion of the retraction cavity containing both vesicles. This portion of the model was then cast in plaster of Paris, and an outer case constructed which represents in a diagrammatic fashion the cellular layer ol the blastocyst wall.

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