The oxygen uptake and carbon dioxide output of late chick embryos

Abstract

Measurements of the oxygen uptake and carbon dioxide output during the last 36 hr. of incubation show that the exchange of these two gases increases progressively from the start of pulmonary respiration until hatching. The evidence indicates that prior to the penetration of the shell by the beak of the embryo (” pipping “) there is marked hypoxia and hypercapnia which are relieved when the embryo gains access to atmospheric air. At the time of hatching there is a very rapid release of carbon dioxide from the body surface and the internal surface of the allantoic membranes. There is no evidence to suggest that its release indicates either hypoxia or hypercapnia in the embryo immediately before hatching.