A QUANTITATIVE STUDY ON BLOOD CLOTTING: PROTHROMBIN FLUCTUATIONS UNDER EXPERIMENTAL CONDITIONS

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Abstract
A method is outlined for the accurate titration of prothrombin in plasma. Normal dog plasma contains sufficient prothrombin to form more than 200 times the concn. of thrombin necessary to clot fibrinogen within a few sec. When blood or recalcified oxalated plasma contains little thromboplastin it clots slowly, and much of this prothrombin remains unutilized. But in blood which contains large amounts of thromboplastin, and hence clots rapidly, the prothrombin is soon depleted by conversion to thrombin. The plasma prothrombin level varies slightly in different dogs, but is remarkably constant in a given animal, even with repeated large hemorrhages or with drastic changes in diet. A marked hypoprothrombinemia is produced by acute chloroform poisoning. The fall in prothrombin precedes the fall in fibrinogen and it returns to normal somewhat more slowly. Phosphorus poisoning also produces a profound fall in both prothrombin and fibrinogen. In cases of severe distemper and of sterile turpentine abscess, the prothrombin level remains normal in contrast to the marked elevation of plasma fibrin. Prothrombin is quantitatively normal in plasmas rendered spontaneously incoagulable by the intraven. administration of peptone, or by the in-vitro addition of heparin. Incoagulable India ink plasma shows but slight reduction.

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