550 



Coagulation o£ Blood 



"induction period." Certain technical difficulties were encountered, and fur- 

 ther work is needed. 



The Titer of Prothrombin and of Thrombin Duri?ig and After Clot Forma- 

 tion: the "Thrombi?! Tide." At the conclusion of the "induction period" 

 prothrombin is consumed and thrombin makes its appearance at a rather 

 rapid rate, and very little difficulty is experienced in recording the changing 

 titer of each substance. The experiments, summarized in table i, are typical. 

 Tube 1, a sample of freshly drawn human blood, was placed at once in the 

 centrifuge. On removal from the machine ten minutes later, the cells were 



TABLE 1 



Prothrombin and Thrombin Titers in Whole Blood Which Was 

 Centrifugalized at Varying Intervals After Being Drawn 



Tube number 



I 



2 



3 



4 

 5 



Time elapsing 



after drawing 



blood, 



minutes* 



ID 

 60 



* Time includes a lO-minute period of centrifugaliz.ation. 



found to be thoroughly packed and the blood to be unclotted. This tube may 

 thus be considered a control, taken near the end of the induction period. The 

 supernatant plasma was found to contain 330 units of prothrombin per cubic 

 centimeter— a level identical with that found in freshly oxalated plasma from 

 this same individual. 



Tube 2 represents freshly drawn untreated blood which was allowed to stand 

 for five minutes, and was then centrifugalized for ten minutes. On removal 

 from the centrifuge, the plasma was found to be clotted, and the prothrombin 

 titer of the plasma had fallen to the 266-unit level. 



Tubes 4 and 5 were allowed to stand for still longer periods before being 

 centrifugalized. From the table, it is seen that the prothrombin titer of the 

 serum fell to the 55-unit level in 1 hour, and to the 6-unit level in 2]4, hours. 



During the period of study 324 units of prothrombin were converted into 

 324 units of thrombin, yet from table 1 it is seen that the thrombin titer 

 ("thrombin tide") did not rise at any time above the 2-unit level. It is evident 

 that the antithrombic activity of serum is so great that thrombin is destroyed 

 almost as rapidly as it is formed. Simple calculation shows that during the 

 latter two-thirds of the first hour thrombin was being formed in each cubic 

 centimeter at the average rate of 5 units, or 5N molecules of thrombin per 

 minute. The thrombin was destroyed at approximately the same rate, and the 



