Abstract
Since Prof. Hara has reported in 1923 that cerium possesed an anticoagulant action, it has been widely recognized that, when rare-earth metals (used in a narrow sense of the term) was given intravenously, it exerted an anticoagulant action for certain period. This time, the author has made a study on the nature of this action on rabbits on the basis of Wohlisch's enzyme theory using the chlorides of La, Ce, Pr and Nd, and found that it was due to the decrease of prothrombin and thrombin contents in blood, which had no relation to the amount of calcium, anti-thrombin and fibrinogen. It possessed also an antagonistic action against the organ preparations of hemostatics and vitamin K which were without any connection with calcium. It had no synergistic action on Heparin, but on Dicumarol. From these facts it can be concluded that the nature of this action resembles to that of Dicumarol.
