The elements of Embryology (1889) The elements of Embryology elementsofembryo00fostuoft Year: 1889 340 THE MAMMALIAN EMBRYO. [chap. equivalent to that of a chick on the fourth day, re- sembles in almost every respect the normal embryos of the Amniota. The cranial flexure is as pronounced as usual, and the cerebral region has now fully the normal size. The whole body soon becomes flexed ventrally, and also somewhat spirally. The yolk-sac (B; ys) forms a small spherical appendage with a long wide stalk, and the embryo is attached by an allantoic stalk with a slight swelling, probably indicating
The elements of Embryology (1889) The elements of Embryology elementsofembryo00fostuoft Year: 1889 340 THE MAMMALIAN EMBRYO. [chap. equivalent to that of a chick on the fourth day, re- sembles in almost every respect the normal embryos of the Amniota. The cranial flexure is as pronounced as usual, and the cerebral region has now fully the normal size. The whole body soon becomes flexed ventrally, and also somewhat spirally. The yolk-sac (B; ys) forms a small spherical appendage with a long wide stalk, and the embryo is attached by an allantoic stalk with a slight swelling, probably indicating the presence of a small hypoblastic diverticulum, to the inner face of the chorion. A detailed history of the further development of the human embryo does not fall within the province of Fig. 113. Figures shewing the Early Changes in the form of the Human Head. (From Quain's Anatomy.) A. Head of an embryo of about four weeks. (After Allen Thomson.) B. Head of an embryo of about six weeks. (After Ecker.) C. Head of an embryo of about nine weeks. 1. mandibular arch ; 1'. persistent part of hyomandibular cleft; a. auditory vesicle.
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