The degeneration of brain thromboplastin in the presence of normal serum.

It has long been known that the " prothrombin " time of a specimen of plasma to which has been added a brain extract thromboplastin depends on the presence of other factors in addition to prothrombin. Biggs, Douglas, and Macfarlane (1953) have demonstrated that both factor V and factor VII take part in a preliminary reaction with the brain extract to produce an activated thromboplastin. Hardisty (1955) believes that the amount ofthromboplastin generated depends on the available factor V, whereas its rate of generation is controlled by factor VII. Experiments described by these workers have shown that mixtures produced by incubating brain extract with factor V, factor VII, and calcium have a thromboplastin content which gradually increases in titre until a maximum is reached, after which there is a rapid deterioration. A similar course of events is observed in the thromboplastin generation test (Biggs and Douglas, 1953) following the incubation of platelets, Christmas factor, antihaemophilic globulin, factors V and VII, and calcium. In all of these tests attention has been focused on the generation of thromboplastin, and its subsequent disappearance seems to have been ignored. The experiments described in the present paper were designed to observe the fate of brain thromboplastin after its activation by normal serum, -nd the results of this work are discussed.