Summary
The biological half-time of factor XII was assessed (a) after transfusion of freshly-drawn,
normal intact ACD-plasma into a patient having Hageman trait and suffering from polycythaemia
vera, and (b) with blocked synthesis in a patient suffering from acute liver dystrophy
due to phosphoric intoxication. The results obtained suggest that the biological half-time
under normal conditions has a value between 50 and 70 hrs.