. Le journal américain de l'anatomie. ich un navire,plus large que la plupart des capillaires, s'étend vers l'embryon-la face antérieure de la veine vitelline. Il est également à noter que, dans l'embryon, entourant theregion dans la zone pellucide, l'spacesbetween les navires sont plus grandes que dans le domaine opaca. Un looksin vain pour tout navire qui pourrait être interprétée comme l'artère mésentérique-vitellin, ou veine vitelline postérieure. À la gauche de theembryo il y a deux ampoules, isolés et plusieurs aveugles. endingvessels À cette référence plus complète sera faite plus tard. Fig. 3 Camera lucida dimensions de la zone d'un vasculosa

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. The American journal of anatomy. ich a vessel, wider than most of the capillaries, extends toward the embryo—the anterior vitelline vein. It is also to be noted that, in theregion surrounding the embryo, in the area pellucida, the spacesbetween the vessels are larger than in the area opaca. One looksin vain for any vessel which might be interpreted as omphalo-mesenteric artery, or posterior vitelline vein. To the left of theembryo there are two isolated blisters, and several blind endingvessels. Fuller reference to this will be made later. Fig. 3 Camera lucida drawing of area vasculosa of an operated chick of 60hours incubation (30 hours after operation). The capillaries in the area pellucidahave begun to break up. H, a hole torn in the blastoderm when mounting, X, at this point the ink was forced out of the tiny vessels by too much pressure, andsettling in the tissues, so obscured the capillaries that they could not be distin-guished. Veil. Vit. Anl., Anterior vitelline vein. DEVELOPMENT OF VESSELS WITHOUT HEART 185. .oor^-c^f, ^^- -_^ VEN. VIT.ANT. r^ X i , HnLl 186 W. B. CHAPMAN Figure 4 is a drawing of an unoperated chick which had beenincubated 48 hours and had developed abnormally. The embryoappears as an oval membrane with two little splotches of proto-plasm underneath it. There was no circulation, and a fairly uni-form capillary plexus was present throughout the area, extendingunder the oval membrane. Only at one place—anterior to themembrane—is there any sign of a vessel larger than a capillary, which is very probably the rudimentary heart and anterior vitel-line veins. There is no trace of any vessel which could be inter-preted as omphalo-mesenteric artery. It will be noted that, as infigure 3, the continuity of the plexus has begun to be lost in thearea to the left of—and posterior to—the embryonic rudiment. In all the operated chicks which were studied, by injection andby combined injection and staining, there was never found anydefinite vessel wh

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• bookcentury1900
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