THE CLOTTING OF THE BLOOD OF AN AMPHIBIAN, BUFO MARINUS LINN

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Abstract
SUMMARY: The blood clotting mechanism of the toad Bufo marinus was investigated in vitro using techniques commonly employed in the study of the prothrombin‐thrombin and fibrinogen‐fibrin stages of human blood coagulation.Clotting of the toad's blood depends upon the presence of calcium ions. The optimum pH is 7·8 and the optimum temperature 35°–40° C. The clot is jelly‐like rather than fibrin‐like and is formed by the coagulation of a “fibrinogen”. Clotted blood becomes fluid again in 2–4 hours through the action of a serum lysin. A prothrombin which is converted quantitatively to a thrombin was demonstrated. The prothrombin is converted by a toad blood leucocyte thromboplastin which is as active as some toad tissue extracts. One‐stage techniques using intrinsic (i.e. blood) sources of thromboplastin revealed no plasma factors similar to human factor V or to anti‐haemophilic globulin. Some of the principles to be followed in the investigation of the blood coagulation mechanism of an animal such as the toad are discussed.

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