THE purpose of this paper is to record certain experiments concerned with the action of anti-coagulants and to bring forward the conclusions which appear to us to arise therefrom. The nomenclature employed will be that of Pawlow and Morawitz. The interpretation we place on their terminology is the following: Thrombin is that body which when calcium-free will coaguilate oxalated blood. Thrombokinase is that body present in tissue extracts which when added to blood hastens its coagulation, but

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... ch when calcium-free will not coagulate oxalated blood. Prothrombin is that body present in blood and in fibrinogen solutions (Mellanby) which when added to thrombokinase and calcium brings about the production of thrombin. The thrombin employed was prepared by Gamgee's method, i.e. by extracting washed fibrin with 5 0/0 NaCl solution. For this purpose sheep's fibrin was used. This always produced a very active thrombin. The tissue extracts were prepared bv pounding tissues with sand and extracting with distilled water. The thymus or testis of a rabbit was the tissue uised. The interpretation of terms given above is an attempt to express the results of experiment without any admixture with theory. That three bodies exist with these attributes is demonstrable, but in giving them names we do not intend to imply any more than if we called them A, B and C. Method. The following method was employed to determine coagulation times. The blood to be investigated was placed on a piece of glass. In certain instances the experiment was conducted at room temperature, in others on the top of a water bath. These instances 9 PH. XLV.