. The comparative anatomy of the domesticated animals. Veterinary anatomy. 1042 EMBRYOLOGY. arise two vessels—the vence omphalo-mesentericce—which enter the posterior extremity of the heart. In Birds there are only two omphalo-mesenteric or vitelline arteries. The circulation in the umbilical vesicle is somewhat ephemeral in several species, and it has been already stated that the vesicle is atrophied at an early jieriod of fcetal life. In Birds it is most extensive ; and its presence may be noted in the Carnivora during the whole term of uterine existence. 2. Development of the heart and vess
. The comparative anatomy of the domesticated animals. Veterinary anatomy. 1042 EMBRYOLOGY. arise two vessels—the vence omphalo-mesentericce—which enter the posterior extremity of the heart. In Birds there are only two omphalo-mesenteric or vitelline arteries. The circulation in the umbilical vesicle is somewhat ephemeral in several species, and it has been already stated that the vesicle is atrophied at an early jieriod of fcetal life. In Birds it is most extensive ; and its presence may be noted in the Carnivora during the whole term of uterine existence. 2. Development of the heart and vessels.—Placental circulation.—The hearty which, until now, was a cylindrical tube, is considerably modified before it attains its complete development. In its different phases, it successively offers all the forms known to exist in vertebrate animals. The first change consists in an inflection ; the tube curves in an S-shaped manner, so that its inferior part becomes superior ; it then dilates at three points : the anterior and superior dilatation situated at the origin of the aorta is named the aortic bulb {bulbus aortce) ; the middle dilatation, the ventricular cavity; and the posterior dilatation, the auri- Fig. 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 Chauveau, A. (Auguste), 1827-1917; Arloing, S. (Saturnin), 1846-1911; Fleming, George, 1833-1901. New York, D. Appleton
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