Abstract
Vit. K1 restored prothrmbin and factors V and VII to normal blood levels in rabbits with dicumarol-induced hypoprothrombinemia as well as rabbits with livers damaged by CCl4 or trypan blue. There was some restoration of these factors even after extirpation of the liver in cats indicating that their synthesis occurs elsewhere, perhaps in the reticulo-endothelial system of the blood-forming organs.