Heparin and the adrenal cortex.

The occasional occurrence of thrombosis after operation has stimulated many attempts to demonstrate an increased coagulability of the blood in the post-operative period. Most of these attempts gave negative or equivocal results, probably because the methods employed were not sensitive enough to record the changes occurring in the complex process of blood coagulation. Nevertheless several investigators (Bergquist, 1945 ; Greig, 1949) reported a shortening of the whole blood clotting time soon after operation. Crafoord (1937), in the course of an investigation into the prevention of post-operative thrombosis by heparin, noted that a given dose of heparin had less effect in prolonging the clotting time in the first 48 hours after operation than in normal people, or in the later post-operative period. It was therefore considered that a new investigation of the coagulability of the blood after operation, as measured by a heparin clotting test, and an attempt to relate the changes observed to the increased activity of the adrenal cortex occurring as a resuit of the "'stress" of operation (Selye, 1950), might be of interest.