In a previous communication dealing with various types of hemorrhagic disease (Whipple1), we suggested that one factor, namely, antithrombin, might be of importance in various types of bleeding. The other elements of blood coagulation were taken up and some of the work on normal blood coagulation was reviewed. Because it is of great importance to have clearly in mind the mechanism of normal blood coagulation, it may be well to detail briefly Howell's2 theory, as it seems to meet all the known requirements in the most satisfactory manner.
This shows in a schematic way the manner of blood coagulation. Howell believes that a small amount of antithrombin is present in the normal plasma and is sufficient to bind the prothrombin and render it inactive. Thromboplastin is set free by cell injury (blood-cells, platelets, tissues, cells,