. The development of the chick; an introduction to embryology . ), all the tul)ules of a given somite do not develop siinul- THE URINOGENITAL SYSTEM 379 taneoiisly: primary tubules are formed in each somite from themost ventral portion of the nephrogenous tissue; then secondarytubules later from an intermediate portion, and tertiary tubuleslater yet from the dorsal portion. Fig. 217 represents a transverse section through the middle. // i^G/om^ £emfp. Fig. 217. — Transverse section through the middle of theWolffian body of a chick embryo of 96 , Aorta. Coel., Coelome. Col.
. The development of the chick; an introduction to embryology . ), all the tul)ules of a given somite do not develop siinul- THE URINOGENITAL SYSTEM 379 taneoiisly: primary tubules are formed in each somite from themost ventral portion of the nephrogenous tissue; then secondarytubules later from an intermediate portion, and tertiary tubuleslater yet from the dorsal portion. Fig. 217 represents a transverse section through the middle. // i^G/om^ £emfp. Fig. 217. — Transverse section through the middle of theWolffian body of a chick embryo of 96 , Aorta. Coel., Coelome. Col. T., Collecting , Glomerulus, germ. Ep., Germinal epithelium. Mst.,Mesentery, n. t., Nephrogenous tissue. T. 1, 2, 3, Primary,secondary, and tertiary mesonephric tubules. V. c. p., Pos-terior cardinal vein. \V. D., Wolffian tluct. of the Wolffian body at the stage of ninety-six hours, showing , secondary, and tertiary tubule. The primary tubuleis typically differentiated; the secondary has formed the secretingtubule and the rudiment of the renal corpuscle, but the tubuledoes not yet open into the Wolffian duct, though it is connectedwith it; the tertiary tul)ule is still in the vesicular stage. Someundifferentiated nephrogenous tissue remains above the rudi-ment of the tertiary tubule, which makes it possible that quar-ternary tul)ules may be formed later. Referring still to the same figure, it will be noted that
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