The evolution of man: a popular exposition of the principal points of human ontogeny and phylogene . plates, and finally lies upon the innersurface of the body-cavity. (Cf Figs. 66-69, u, vol. i. p. 277,and Figs. 95-98, p. 319; also Plate IV. Figs. 3-6, u.) Whilethe primitive kidney duct is thus making its way inward,on its inner and under side appear a large number of smallhorizontal tubes (Fig. 319, a), exactly corresponding to thesegmental canals of the Myxinoides (Fig. 317, h). Like thelatter, these are, probably, originally protuberances of theprimitive kidney ducts (Fig. 316, u). At the
The evolution of man: a popular exposition of the principal points of human ontogeny and phylogene . plates, and finally lies upon the innersurface of the body-cavity. (Cf Figs. 66-69, u, vol. i. p. 277,and Figs. 95-98, p. 319; also Plate IV. Figs. 3-6, u.) Whilethe primitive kidney duct is thus making its way inward,on its inner and under side appear a large number of smallhorizontal tubes (Fig. 319, a), exactly corresponding to thesegmental canals of the Myxinoides (Fig. 317, h). Like thelatter, these are, probably, originally protuberances of theprimitive kidney ducts (Fig. 316, u). At the blind, innerend of each of the primitive urinary tubes an arterialglomerulus is formed, which grows into this blind endfrom within, forming a vascular coil. The glomerulusto a certain extent expands the bladder-like blind endof the small urinary tubes. As the primitive urinary tubes, HtJDIMENTAilY PRIMITIVE KIBNEYS. 409 which are, at first, very short, grow longer and broader,each of the two primitive kidneys assumes the form of asemi-pinnate leaf (Fig. 320). The urinary tubes (it) repre- i e i. Fig. 319.—Eudimentaiy primitive kidney of embryonic Dog. The pos-terior portion of the body of the embryo is seen from the ventral side,covered by the intestinal layer of the yelk-sac, which has been torn away,and thrown back in front in order to show the primitive kidney ducts withthe primitive kidney tnbes (a) : h, primitive vertebrae; c, dorsal medulla ;d, passage into the pelvic intestinal cavity. (After Bischoff.) Fig. 320.—^Primitive kidney of a human embryo : u, the urine-tubes ofthe primitive kidney; w, Wolffian dact; iv, upper end of the latter (Mor-gagnis hydatid) ; m, Miilleiian duct; m, upper end of the latter (Fallopianhydatid) j g, hermaphrodite gland. (After Kobelt.) sent the tissue and the primitive kidney duct (iv) themid-rib. On the inner margin of the primitive kidney therudiment of the hermaphrodite sexual gland already 4^0 THE EVOLUTION OF MAN. appears as a body
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Keywords: ., bookcentury1800, booksubjectembryologyhu, booksubjecthumanbeings
