. The science and art of midwifery. nother. The first, next to the veins, is termed theauricular portion, the middle one is the ventricular, and the last,which is the primitive arterial trunk, is named the bulbus arteriosus (Quain). Fig. 63. The bulbus arteriosus divides into two branches, which convey the* A. Kolliker, Entwickelungs-Geschichte, 2te Auflage, p. 159. 70 PHYSIOLOGY OF THE OVUM. blood from the heart upward to the first (upper) visceral arch. Atthis point, which corresponds to the future base of the brain, theycurve backward and then take a downward course in front of thechorda do
. The science and art of midwifery. nother. The first, next to the veins, is termed theauricular portion, the middle one is the ventricular, and the last,which is the primitive arterial trunk, is named the bulbus arteriosus (Quain). Fig. 63. The bulbus arteriosus divides into two branches, which convey the* A. Kolliker, Entwickelungs-Geschichte, 2te Auflage, p. 159. 70 PHYSIOLOGY OF THE OVUM. blood from the heart upward to the first (upper) visceral arch. Atthis point, which corresponds to the future base of the brain, theycurve backward and then take a downward course in front of thechorda dorsalis. These two branches of the bulbus arteriosus aretermed the superior vertebral arteries. They are likewise known asthe aortic arches. Beneath the level of the heart they unite for a shortdistance to form a common trunk, which in turn again divides intotwo branches, termed the inferior vertebral arteries. These latter runparallel to one another, on each side of the future vertebral column, tothe caudal extremity of the *-i 5 5 Fig. 63.—Diagram of heart and first arterial vessels (Quain). A, at a period correspondingto the thirty-sixth or thirty-eighth hour of incubation; B and C\ at the forty-eighthhour of incubation. 1,1, primitive veins • 2, auricular part of heart; 3, ventricular part;4, aortic bulb ; 5, 5, aortic arches—in C, their coalescence is shown at a ; in B, below theupper 5, the second aortic arch is formed, and farther down the dotted lines indicate theposition of the succeeding arches ; 5, 5, continuation of main vessels (inferior vertebral);G, G, omphalo-mesenteric arteries. In their course the inferior vertebral arteries give off branches whichare at first limited to the area germinativa by a circular vein, termedthe sinus terminalis. The veins, which return the blood to the embryo,occupy a lower stratum than the arteries, and empty into two shorttrunks, communicating with the auricular extremity of the the sinus terminalis
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Keywords: ., bookcentury1800, bookdecade1890, bookidsci, booksubjectobstetrics
