. L'embryologie chimique. L'embryologie. Extraits azotés 1147 contient autant que l'embryon. En conséquence le graphique ressemble à celui de glycogène, car c'est du type dans lequel le montant total de la substance augmente, tandis que la quantité de la substance à l'extérieur de l'embryon première augmente et diminue. Sans doute la raison pour laquelle le jaune a tellement c'est que la résorption du sac vitellin et ses navires ont été inclus dans l'analyse, et par conséquent la bases puriques de la nucléoprotéine de leurs cellules ont été inclus. Mendel &AMP ; Levain- ont aussi estimé les purines dans l'œuf, et de leurs f

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. Chemical embryology. Embryology. NITROGENOUS EXTRACTIVES 1147 contains as much as the embryo. The graph accordingly resembles that for glycogen, for it is of the type in which the total amount of the substance increases, while the amount of the substance outside the embryo first increases and then decreases. Probably the reason why the yolk has so much is that the yolk-sac and its vessels were included in the analysis, and consequently the purine bases from the nucleoprotein of their cells were included. Mendel & Leaven- worth have also estimated the purines in the avian egg, and their figures, which appear in Fig. 343, agree with Sendju's as demonstrating a vigorous syn- thesis, although in absolute value they much exceed his, by 22-0 to 7'0 on the last day of develop- ment. This is due to the fact that Mendel & Leavenworth probably included the uric acid present. Mendel & Leavenworth sepa- rated a number of the individual bases by the Kruger-Schmid pro- cess, with the results shown in Fig. 344. Kossel's original figures are placed beside them for comparison. The concentration of the bases in the embryonic tissue was, it seemed, about the same as in adult tissue, thus: Grams % wet weight Mendel 8c Leavenworth © Guanine "j e Adenine >WhoU ® HypoxanbhineJ Kosse O Guanine 1 O HypoxanbhineJ. Days -* 5 Fig. 344. Hypo- > Guanine Adenine xanthine Xanthine Cow muscle: embryo 0-044 — 0-038 0-012 Kossel, 1884 adult 0-005 — 0-053 0-012 Pig muscle: embryo (100 mm.) 0-093 0-065 0-029 Mendel'& adult 0-027 0-059 — Leavenworth 1908 Wells & Corper remarked in 1909 that foetal tissues seemed to con- tain much more guanine than adenine, since on autolvsis they gave twice as much xanthine as hypoxanthine. No more recent investi- gations have been made exactly along these lines, but Calvery has reported the presence of pentose nucleic acid with its pyrimidine, . Please note that these images are extracted from scanned page images that may have be

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