. Chemical embryology. Embryology. 68o THE RESPIRATION AND [PT. Ill is not regular, but has certain definite points of transition, and tends to approximate rather to a series of straight Hues than to a segment of a curve. The findings of Parnas & Krasinska, then, were in a sense a return to the original interrupted curves of Bataillon. The respira- tion of the amphibian embryo, said Parnas & Krasinska, during the segmentation, morula, and blastula stages, is proportional to the time passed and uniformly rising. The increase in the number of cells is certainly accompanied by an increase
. Chemical embryology. Embryology. 68o THE RESPIRATION AND [PT. Ill is not regular, but has certain definite points of transition, and tends to approximate rather to a series of straight Hues than to a segment of a curve. The findings of Parnas & Krasinska, then, were in a sense a return to the original interrupted curves of Bataillon. The respira- tion of the amphibian embryo, said Parnas & Krasinska, during the segmentation, morula, and blastula stages, is proportional to the time passed and uniformly rising. The increase in the number of cells is certainly accompanied by an increase in the respiration. But at 250. 6a Hours Fig. 131, (Upper line = in air; lower line = in oxygen.) the time of gastrulation, there is a marked rise in the gaseous exchange (see Fig. 132), and a further powerful acceleration of it is seen at the time of the formation of the medullary plate, after the embryo has formed its longitudinal axis. "The first cleavage processes", said Parnas & Krasinska, "and the dividing of the embryo into poten- tially different cells proceeds with a uniform amount of respiration, but the differentiation of the germ-layers first of all, and then, the formation of structurally and chemically different cells, are accom- panied by enhanced metabolic intensity and therefore by an in- creased respiration. After the neurula has been formed there is little i. 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 Needham, Joseph, 1900-. New York: The MacMillan Co.
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