All published values of the metabolic rates of avian embryos are brought together for analysis. A generalized pattern of O2 consumption during development of precocial eggs is determined and used to estimate the total amount of O2 consumed duirng development. The metabolic rates of avian eggs just prior to internal pipping (preIP MO2 is inversely proportional to the length of the incubation period. As in mammals, the mass specific metabolism of avian embryos is approximately equal to that of their parents, even though the parents are at least five times heavier. The total amount of O2 consumed per gram of fresh egg mass during development appears to be independent of egg mass and incubation period and averages 102 cm3 O2 . G-1. Calculated air cell O2 and CO2 tensions average 101 Torr and 40 Torr, respectively. Calculated air cell gas tensions are significantly correlated with egg mass but directly observed values are not, a discrepancy which remains to be resolved.
Animals Birds