. Analysis of development. Embryology; Embryology. Fig. 118. Progressive localization in the chick of heart muscle and nephros (Butler, '35; Rudnick, '32, '38b,c; Rawles, '43). The situation in the un- incubated blastoderm is somewhat uncertain; it is possible that some localization exists even then. It is established that as soon as the piimitive streak appears (5,C), a limited area only can form cardiac muscle in vitro or in grafts (D,E), and that imtil the head-process stage the median part of this area is most active. In E and G the boundaries of the areas have been carefully determined; i
. Analysis of development. Embryology; Embryology. Fig. 118. Progressive localization in the chick of heart muscle and nephros (Butler, '35; Rudnick, '32, '38b,c; Rawles, '43). The situation in the un- incubated blastoderm is somewhat uncertain; it is possible that some localization exists even then. It is established that as soon as the piimitive streak appears (5,C), a limited area only can form cardiac muscle in vitro or in grafts (D,E), and that imtil the head-process stage the median part of this area is most active. In E and G the boundaries of the areas have been carefully determined; in the other stages, they are somewhat conjectural, the shaded areas representing positive cases. structiu-es: heart and nephros. Heart-forming areas (, those which will form cardiac muscle) follow fairly well the course that would be expected of invaginating lateral mesoderm, as probably does the more pos- terior nephric field. A comparison of the various diagrams for the definitive primitive streak stage (Figs. lUE, 118D, F) shows a remarkable concentration of potencies in the immediate vicinity of Hensen's node: an expression of the experimental fact that grafts from this center develop into larger, more varied masses than do more lateral or anterior or posterior regions; the medianmost. Fig. 119. Localization of entodermal potencies: A-C from Luther ('36a); D-F from Butler ('35), Rudnick and Rawles ('37); G~J from Rudnick ('32) and Rawles ('36); data all from grafts. In the chick material, lateral and posterior limits of areas have not been determined in stages earlier than the head process. In D-F, the shading indicates gut not formed into recognizable organ units; crosses, or- ganized small intestine; circles, identifiable seg- ments of 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 Willier
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Keywords: ., bookcentury1900, bookpublisherphiladelphi, booksubjectembryology
