A STUDY OF A RECONSTITUTED HYPOPHYSIS AND ITS FUNCTION IN CHIMERIC BIRD EMBRYOS

Experiments consisting in replacing the encephalon of a chick embryo b y that of a quail embryo at the same stage of development were realize d on 42 hour-old (12-15 somites) embryos. They led to the development of chimaeras. The reconstitution of the embryonic head concerned all t erritories. More peculiarly, the hypophysis is composed of two parts b elonging to the host (adenohypophysis) and to the grafted tissue (neur ohypophysis). Immunocytological reactions displayed some hormones, lik e ACTH and oxytocin which are normally secreted. It may be assumed tha t a reconstituted hypophysis is able to secrete hormones as does a nor mal one. On the other hand, some hormones, like vasopressin, are not s ecreted.