. A laboratory manual and text-book of embryology. Embryology. LATERAL DISSECTION OF THE VISCERA I05 Bulbu5 cordis cephalad and ventrad the allantoic stalk. This is at first a narrow tube but soon expands into a vesicle of large size, a portion of which is seen in Fig. go. Dorso- laterad the cloaca receives the primary excretory (Wolffian ducts). The hind-gut is continued into the tail as the tail-gut (post-anal gut) which dilates at its ex- tremity as in the mm. pig described by Thyng. The mid-ventral wall of the cloaca is fused to the adjacent ectoderm to form the cloacal membrane. In th
. A laboratory manual and text-book of embryology. Embryology. LATERAL DISSECTION OF THE VISCERA I05 Bulbu5 cordis cephalad and ventrad the allantoic stalk. This is at first a narrow tube but soon expands into a vesicle of large size, a portion of which is seen in Fig. go. Dorso- laterad the cloaca receives the primary excretory (Wolffian ducts). The hind-gut is continued into the tail as the tail-gut (post-anal gut) which dilates at its ex- tremity as in the mm. pig described by Thyng. The mid-ventral wall of the cloaca is fused to the adjacent ectoderm to form the cloacal membrane. In this region later the anus arises (Fig. 100). The post-anal gut soon disap- pears. The urogenital organs consist of the mesonephroi, the mesonephric ducts, the anlages of the metanephroi, the cloaca and the allantoic. The form of the mesonephroi is seen in Figs. 90 and 92. Each consists of large vascular glom- eruli associated with coiled tubules fined with cuboidal epithelium and opening into the mesonephric duct (Figs. 107 and 109). The Wolffian ducts beginning at the anterior end of the mesonephros curve at first along its ventral, then along its lateral surface. At its caudal end each duct bends ventrad and to the midline, where it opens into a lateral expansion of the cloaca. Be- fore this junction takes place, an evagination into the mesenchyme from the dorsal wall of each mesonephric duct gives rise to the anlages of the metanephroi, or permanent kidneys. A slight thickening of the meso- thelium along the median and ventral surface of each mesonephros forms a light-colored area, the genital fold (Fig. 91). This area is pointed at either end and confined to the middle third of the kidney. It is the anlage of the genital gland from which either testis or ovary is developed. Blood Vascular System.—The heart lies in the pericardial cavity as seen in Fig. 91. The atrial region (Fig. 94), as in the mm. human embryo, has given rise to two lateral sacs, the right and left at
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectembryology, bookyear1
