A manometric analysis of the metabolism in avian ontogenesis. III.—The respiratory quotient of the yolk-sac and allantois during the last two weeks of development

Abstract

Experiments previously reported (Needham, 1932, a, b, c ) have thrown some light on the metabolism of the chick embryo and its accessory structures by manometric determinations of respiratory quotient. These determinations, however, were confined to the blastoderm ( area opaca and area pellucida ) up to the 60th hour of incubation, of the embryo up to the 6th day, and of the yolk-sac between 2½ and 7 days of development. In order to complete the picture, it was necessary to carry out similar determinations on the yolk-sac during the remainder of development and on the allantois, from its first appearance before the 5th day to the time of hatching. These form the subject of the present paper. The extra embryonic membranes of the later stages of development are in some respects easier to deal with than those of the first week. But although they become less fragile they also become more heterogeneous, until at last it may be difficult, if not impossible, to select any portion of the yolk-sac, for example, which shall be representative of the system as a whole. This difficulty will be referred to below. On the other hand, the value of the membranes as sheets of living cells which can be studied manometrically without even the minor degree of traumatism involved in the cutting of razor-slices, should not be underestimated.