. The elements of embryology . Embryology. Diagrammatic longitudinal section through the pos- terior END OF AN Embryo Bird, at the tme of the Formation on the Allantois. ep. epiblast; Sp.c. spinal canal; oh. notoohord; n.e. neurenterio canal; hy. hypoblast; p.a.g. postanal gut; pr. remains of primitive streak folded in on the ventral side ; al. aUantois ; me. mesoblast; an. point where anus will be formed; p.c. perivisceral cavity; am. amnion; so. somatopleure; ap. splanohnopleure. does not last long, but even after its rupture there re- mains a portion of the canal continuous with the gut ; t

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. The elements of embryology . Embryology. Diagrammatic longitudinal section through the pos- terior END OF AN Embryo Bird, at the tme of the Formation on the Allantois. ep. epiblast; Sp.c. spinal canal; oh. notoohord; n.e. neurenterio canal; hy. hypoblast; p.a.g. postanal gut; pr. remains of primitive streak folded in on the ventral side ; al. aUantois ; me. mesoblast; an. point where anus will be formed; p.c. perivisceral cavity; am. amnion; so. somatopleure; ap. splanohnopleure. does not last long, but even after its rupture there re- mains a portion of the canal continuous with the gut ; this, however, constitutes a purely embryonic and tran- sient section of the alimentary canal, and is known as the postanal gut. Immediately in front of it is a deep infolding of the epiblast, which nearly meets the hypoblast (Fig. 61, an) and forms the rudiment of the anus and of the outer section of the cloaca into which the bursa Fabricii opens in the adult. It is known to embryologists as the proctodoeum, but does not open into the alimentary tract till considerably later. 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 work.. Foster, M. (Michael), Sir, 1836-1907; Balfour, Francis M. (Francis Maitland), 1851-1882; Sedgwick, Adam, 1854-1913; Heape, Walter, 1855-1929. London ; New York : Macmillan