Histochemical observations on the enzymes of chicken yolk sac membrane

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Abstract
In the endodermal cells of the yolk sac membrane of chicken embryos incubated for 12 to 18 d, the activity of glucose‐6‐phosphatase (G‐6‐Pase) was high, the activity of acid phosphatase (Acid Pase) was moderate, the activities of lactate dehydrogenase (LDH) and of glyceraldehyde‐3‐phosphate dehydrogenase (G‐3‐PDH) were low, and succinate dehydrogenase (SDH) and alkaline phosphatase (Alk Pase) activities were not detected. On the day before hatching, however, SDH became evident with low activity, and the activities of Acid Pase, LDH and G‐3‐PDH increased and remained higher until the day after. Five days after hatching, there were marked decreases in the activities of all the enzymes except SDH. Alk Pase was not detected at any time. The function of the yolk sac endo‐derm in the absorption of yolk is discussed in the light of these observations.