Antagonistic Ions in Blood Coagulation. 



7 



water with the addition of CaCl 2 no longer produces thrombin, it 

 must be concluded that the removal of the fatty portion of the 

 cell membranes has rendered them non-sensitive to calcium, a 

 point of view which harmonizes with the experiments on aqueous 

 oil systems reported in the previous papers. As a further proof 

 that thrombin is derived from cells suspended in the plasma which 

 remain intact so long as the proportion of citrate to calcium exceeds 

 2.5 : 1, we followed the procedure recently adopted by Cramer 1 in 

 studying oxalate plasmas, and filtered the citrated plasma through 

 a bougie before the addition of calcium. It was found that the 

 filtered citrated plasma was easily coagulated by thrombin but 

 could not be precipitated by an excess of calcium even after a 

 period of 24 hours. The residue on the filter was washed with salt 

 solution containing a small amount of citrate, was then washed 

 back by means of water pressure, and the aqueous suspension thus 

 obtained divided into two parts. One part was treated with a 

 slight excess of calcium, and when added to filtered plasma con- 

 taining a large excess of citrate immediately caused coagulation 

 from which it must be concluded that thrombin had been liberated 

 by the calcium from cells incapable of passing through the bougie. 

 The second portion was divided into two parts both of which 

 were precipitated by means of acetone-ether following the pro- 

 cedure outlined above, the calcium chlorid being added in one case 

 before and in the other case immediately after the addition of 

 the acetone ether. The same results were obtained as in the 

 previous case. The portion treated with calcium before precipita- 

 tion rapidly coagulated filtered citrate plasma containing an excess 

 of citrate. The second portion precipitated after the addition of 

 calcium, exerted absolutely no effect upon the citrated plasma. 

 From these experiments we are justified in concluding that 

 thrombin is contained in blood platelets and possibly leukocytes 

 suspended in the plasma, that the addition of a sufficient pro- 

 portion of calcium to disturb the colloidal equilibrium of the 

 lipoids in the cell membranes brings about the liberation of the 

 thrombin, which in its turn causes precipitation of the fibrinogen, 

 this later process being presumably entirely independent of calcium 

 since it takes place rapidly in the presence of a large excess of 



1 Quarterly of Exper. Physiology, Vol. VI, p. 1. 



