The Effect of Foreign Surfaces on Blood Coagulation 12

In the United States, the two-stage theory of blood coagulation is widely accepted. This theory recently reviewed by Quick (1) and Eagle (2) sug-gests that in the first stage prothrombin, calcium ion and thromboplastin interact to form thrombin. Thrombin, in the second stage, converts fibrinogen to fibrin. Plasma thromboplastin has been con-sidered to be of platelet origin. The phenomenon of the initiation of coagulation when blood is shed has been considered by many investigators to be due to the disintegration of platelets with the re-lease of thromboplastin. It has been known for many years that the co-agulation time of blood taken in paraffin tubes is much longer than that of blood taken in glass tubes. The explanation usually offered for this phenomenon is that the glass, acting as a foreign surface, destroys the platelets at a more rapid rate than occurs in the presence of paraffin. The in-creased amount of thromboplastin so liberated is then considered to be responsible for the shorter coagulation time in glass vessels. Nolf (3) has criticized this explanation. He states that his ex-perimental data indicate that cell- and platelet-free plasma already contains all of the factors necessary for blood coagulation. He believes that the initia-tion of coagulation is the result of the direct modi-fication of one or more of the constituents of cell-free plasma by contact with a foreign surface such as glass. In view of this difference of opinion, it seemed advisable to reinvestigate the role which foreign surfaces play in the blood coagulation reaction.