Factors Associated with Lesions of the Brain that Follow Intravenous Injection of Thromboplastic Substance *

The symptomatology and pathology of lesions of the brain following the injection of thromboplastic substance, as has been pointed out,10 cannot be attributed exclusively to thrombi or emboli in the cerebral vessels. The quick recovery from unconsciousness and the absence of thrombi in the cerebral vessels as well as the general nature of the lesions indicate rather that a temporary disturbance of the cerebral circulation may be of significance. In support of this concept is the fact that thromboplastic substance exerts a profound influence upon the coagulation time of the blood as well as upon the circulating blood volume, as indicated by changes in blood pressure and in the fluid and protein contents of the blood. A sharp fall in pressure accompanied by increased red cell volume and loss of plasma protein occurs in a manner similar to that noted following the injection of histamine.8 It would appear, therefore, that changes in circulatory dynamics with the consequent anoxia, as well as the thrombotic phenomena must be considered as factors in the production of these cerebral lesions. The experiments to be reported were designed to determine the relative importance of these two factors and to ascertain, if possible, whether there were still others to be considered in the interpretation of brain lesions produced by the injection of tissue extracts.