(1) Antihemophilic globulin (AHG) consumption has been studied in normal blood maintained at 37 C. for one hour after collection. By the end of one hour the AHG was completely utilized.
(2) AHG consumption is defective completely in Christmas disease and heparin therapy, and to a lesser degree in phenylindanedione therapy. In platelet deficiency consumption of AHG is normal.
(3) A possible interpretation of these results is discussed in relation to the order of the interactions involved in blood thromboplastin formation.