. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 222 DEVELOPMENT OF THE BLOOD-VESSELS themselves to form an enclosing wall, and the cords, increasing in size, unite together to form a network of vessels in which float the spherical cells which may be known as mesamceboids (Minot). Viewed from the surface at this stage a portion of the vascular area of the mesoderm would have the appearance shown in Fig. 130, revealing a dense network of canals in which, at intervals, are groups of mesamaeboids adherent to the walls, constituting what have b
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 222 DEVELOPMENT OF THE BLOOD-VESSELS themselves to form an enclosing wall, and the cords, increasing in size, unite together to form a network of vessels in which float the spherical cells which may be known as mesamceboids (Minot). Viewed from the surface at this stage a portion of the vascular area of the mesoderm would have the appearance shown in Fig. 130, revealing a dense network of canals in which, at intervals, are groups of mesamaeboids adherent to the walls, constituting what have been termed the blood-islands, while in the meshes of the network unaltered mesoderm cells can be seen, forming the so-called sub- Fig. 129.—Transverse Section through the Area Vasculosa of Rabbit Embryos showing the Transformation of Mesoderm cells into the Vascular Cords. Ec, Ectoderm; En, endoderm; Me, mesoderm.—{van der Stricht.) At the periphery of the vascular area the vessels arrange them- selves to form a sinus terminalis enclosing the entire area, and the vascularization of the splanchnic mesoderm gradually extends toward the embryo. Reaching it, the vessels penetrate the embry- onic tissues and eventually come into connection with the heart, which has already differentiated and has begun to beat before the connection with the vessels is made, so that when it is made the circulation is at once established. Before, however, the vasculariza- tion reaches the embryo some of the canals begin to enlarge ( Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original McMurrich, J. Playfair (James Playfair), 1859-1939. Philadelphia : P. Blakiston's son & co.
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