. The American journal of anatomy. aper. IV. DESCRIPTION OF THE EXTRA-EMBRYONIC VASCULAR SYSTEiMOF EMBRYOS STUDIED The appearance of the embryo at the stage of operation isshown fairly well in figure 1, which represents an embryo slightlybeyond the operative stage At this period the blood cells havenot acquired their hemoglobin and no vessels are visible underthe binocular. The embryo appears to be floating free withinthe clear area pellucida, and the area opaca is apparent only asa wide milky-white band around the area pellucida. The bloodvessels in the embryo proper of chicks of this age hav
. The American journal of anatomy. aper. IV. DESCRIPTION OF THE EXTRA-EMBRYONIC VASCULAR SYSTEiMOF EMBRYOS STUDIED The appearance of the embryo at the stage of operation isshown fairly well in figure 1, which represents an embryo slightlybeyond the operative stage At this period the blood cells havenot acquired their hemoglobin and no vessels are visible underthe binocular. The embryo appears to be floating free withinthe clear area pellucida, and the area opaca is apparent only asa wide milky-white band around the area pellucida. The bloodvessels in the embryo proper of chicks of this age have beenstudied by Miss Sabin (T7) through injectiods of India ink intothe aorta and larger vessels, and her results have already beenreferred to. As previously mentioned, and as shown in figure 1, the vesselsof the extra-embryonic region consist of a dense capillary netextending from the embryo to the sinus terminalis at the timethe circulation begins. Anteriorly, the sinus terminalis breaks DEVELOPMENT OF VESSELS WITHOUT HEART 181. Fig. V Camera lucida drawing of an injected, normal chick of 35 hours incu-bation, 16 somites, cleared in oil of wintergreen, viewed from above. The lefthalf of the area is shown. Enl. 12t X. 1 The chick shown in figure 1 was incubated houis, but in development hasreached the stage usually seen in chicks of about 38 hours incubation. It is,therefore, slightly older than most of the chicks at the time of operation. The inkwas injected into the sinus terminalis and forced through the capillary net, or,as I have termed it in the text, the venous plexus of capillaries anterior to theembryo, to the rudimentary vitelline veins. Ink was also introduced into theheart. The heart pumped the ink back and forth into the sinus and vitellineveins for several minutes, but soon particles of the ink began to shoot through thearches into the right dorsal aorta. This was followed quickly by a rapidly grow-ing stream of ink which moved forward as propelled*by the pu
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Keywords: ., bookauthorwi, bookcentury1900, bookdecade1910, booksubjectanatomy
