The Development of Cytochrome Oxidase in the Chick Embryo*

Studies on the development of enzyme systems with time in animal embryos are relatively rare. Especially is this true of the chick embryo, of which the only complete study of enzyme development appears in the work of Levy and Palmer (1) on dipeptidase accumulation. According to these authors, dipeptidase activity in the chick increases with time and this increase is correlated with the accumulation of total nitrogen which presumably comes from the yolk. The same kind of correlation between nitrogen increase and enzyme activity has been demonstrated in oat seedlings for catalase and dehydrogenase activity by Albaum, Donnelly, and Korkes (2). In the chick, cytochrome c does not appear until about the 4th day, according to Yaoi (3), and Potter and DuBois (4) were unable to detect it until about the 6th day. The present work was undertaken to ascertain when the enzyme, cytochrome oxidase, which usually operates with cytochrome c as part of the same system, appears and how its concentration changes during the course of early development.