. The development of the chick; an introduction to embryology. Birds -- Embryology. ALIMENTARY TRACT AND ITS APPENDAGES 315 from the intermediate section of the cloaca or urodaeum; this is a relatively short division of the cloaca which receives the renal and reproductive dvicts in its dorsal wall by two pairs of openings; it is bounded from the larger anterior division, coprodseum, by a rather low circular fold; the coprodseum passes gradually, with- out a sharp line of division, into the rectum. The early embryological history of these parts has been con- sidered in the preceding chapters. T


. The development of the chick; an introduction to embryology. Birds -- Embryology. ALIMENTARY TRACT AND ITS APPENDAGES 315 from the intermediate section of the cloaca or urodaeum; this is a relatively short division of the cloaca which receives the renal and reproductive dvicts in its dorsal wall by two pairs of openings; it is bounded from the larger anterior division, coprodseum, by a rather low circular fold; the coprodseum passes gradually, with- out a sharp line of division, into the rectum. The early embryological history of these parts has been con- sidered in the preceding chapters. The condition on the fourth day is shown in the accompanying figure (Fig. 183) representing a Fig. 183. — Median sagittal section of the hind end of a chick embryo on the fourth day of incubation. (After Gasser from Maurer.) All., AUantois. Am., Tail fold of amnion, cl. M., Cloacal mem- brane. CI., Cloaca. N'ch., Notochord. , Neural tube. R., Rec- tum. Y. S., Wall of yolk-sac. sagittal section of the hind end of the embryo. The cloaca is the large terminal cavity of the intestine, closed from the exterior by the cloacal membrane, in which the entoderm of the floor of the cloaca is fused to the superficial ectoderm at the base of the tail. The line of fusion is a long, narrow median strip, extending from just below the neck of the allantois to the hinder end of the cloaca. Leading out from the cloaca ventrally, in front of the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lillie, Frank Rattray, 1870-1947. New York, Holt


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