On Phosphorus Metabolism in Embryonic Life

1. The chick embryo possesses the power of synthesizing creatinephosphate from phosphopyruvic acid and creatine with adenylic acid as phosphate transporter. 2. This reaction has been followed back into the early stages of development. At the 43 rd hour (approximately the beginning of cardiac activity) it is present in an unweakened state. At the 23rd hour (during the closure of the neural folds), although phosphopyruvic acid is dephosphorylated by adenylic acid, phosphagen synthesis is exceedingly weak. 3. At no age does the synthesis of argininephosphate occur in the chick embryo. The significance of this and the above facts is discussed in the text.