The development of the human body; a manual of human embryology . Fig. 46.—Embryo of from Twenty to Twenty-fivB Days. A m, Amnion; LL, lower limb ; UA, umbilical artery; Uc, umbilical cord; UL, upper limb; Ys, yolk-sac.—(Coste.) 96 THE DEVELOPMENT OF THE HUMAN BODY. small elevations of the sides of the body, one almost oppo-site the neck bend and the other opposite the sacral bend,are the first indications of the limbs (Ul and LI); and theeyeball and ear vesicle (au), which were present thoughnot very evident in earlier stages, are now plainly visiblein surface views. In the next stage—as a ty
The development of the human body; a manual of human embryology . Fig. 46.—Embryo of from Twenty to Twenty-fivB Days. A m, Amnion; LL, lower limb ; UA, umbilical artery; Uc, umbilical cord; UL, upper limb; Ys, yolk-sac.—(Coste.) 96 THE DEVELOPMENT OF THE HUMAN BODY. small elevations of the sides of the body, one almost oppo-site the neck bend and the other opposite the sacral bend,are the first indications of the limbs (Ul and LI); and theeyeball and ear vesicle (au), which were present thoughnot very evident in earlier stages, are now plainly visiblein surface views. In the next stage—as a type of which an embryo. Fig. 47.—Embryo mm. , Lower limb; U, umbilical cord; Ul, upper limb; Y, yolk-sac.—(His.) figured by Coste (Fig. 46) may be taken—the three bendsof the body mentioned above have greatly increased, sothat the head and tail of the embryo are almost in contactand the latter is bent a little toward one side. The closureof the ventral surface of the body is almost completed and THE EXTERNAL FORM OF THE BODY. 97 the margins of the umbilicus have begun to be prolongedventrally so as to enclose the yolk-stalk and belly-stalkin the umbilical cord. The yolk-sac has increased con-siderably in length and the differentiation of its extra-embryonic portions into a yolk-stalk and yolk-vesicle isplainly distinguishable. The limb rudiments have in-creased somewhat in size, and, in addition to the eyeballand ear vesicle, a third sense-organ has made its appear-ance in the form of two pits situated on the under side ofthe anterior portion of the head; these pits are the firstindications
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
