. Chemical embryology. Embryology. 1074 PROTEIN METABOLISM [PT. Ill. Fig. 311. with a few later figures of Nakamura, which are not concordant. Concentrating attention on Fig. 311 for the moment, it can be seen that the wet weight curve, after a peak on the 6th day and a depres- sion on the gth, gains a plateau and remains there for the rest of development. The dry weight curve presents the same peak and the same depression, but, since the embryo is growing much drier as it increases in size, the dry weight curve drops away steadily after the loth day. It is significant that there is a very vig
. Chemical embryology. Embryology. 1074 PROTEIN METABOLISM [PT. Ill. Fig. 311. with a few later figures of Nakamura, which are not concordant. Concentrating attention on Fig. 311 for the moment, it can be seen that the wet weight curve, after a peak on the 6th day and a depres- sion on the gth, gains a plateau and remains there for the rest of development. The dry weight curve presents the same peak and the same depression, but, since the embryo is growing much drier as it increases in size, the dry weight curve drops away steadily after the loth day. It is significant that there is a very vigorous period of pro- tein absorption^ before the 5th day, and another from the 14th to the 18th days. The depression in the curves of Fig. 311 comes just between the two maxima of protein absorption. The amount of non-protein nitrogen in 100 gm. of embryo is related, then, to the amount of protein nitrogen which 100 gm. of embryo is receiving from the rest of the egg. Reference to Fig. 250 illustrates this. Another curve which is worth studying is the curve for non- protein nitrogen in percentage of the total nitrogen (Table 136 and Fig. 312). Low at first, the value rises to attain a peak on the Gth day, and thereafter falls, except for a slight oscillation about the gth day, probably comparable in cause with those noted as occurring at the same time in the curves for Fig, 312. non-protein nitrogen as percent- ages of wet and dry weight. It may be said, then, that, though little change seems to take place in the non-protein nitrogen outside the embryo, yet, inside it, definite peaks are found, and that these corre- spond with the periods of greatest intensity of protein absorption, such 1 This does not, of course, mean absorption of intact protein; see pp. 920 ff. 0 ® Needham -l 0 Murray e Sznerovna -3 ® ® Le Breton 8t ^ ro Schaeffer "^ ^ \ 0 Fridericia -^ I H 0 -S / \® e 0 ° / \ ® 'â¢^ i V^ P ~n 0 0 -I f 0 >D ® e e - 5 -S 0 \ 0 'â ' e \®eÂ
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