Paradoxical Shortening of Blood Coagulation 131 



believe that it is dependent upon some effect on the blood 

 platelets, which are not directly destroyed by the citrate but are 

 damaged by contact with it and are then removed from the 

 circulation by the spleen where they are destroyed and their 

 thromboplastic contents gradually liberated into the circulating 

 blood. This theory is based upon the following observations : 



1. In the test tube, sodium citrate does not destroy the 

 platelets, but it effects them so that they are actually preserved 

 and therefore more easily counted. 



2. Within a few minutes after the intravenous injection of 

 sodium citrate the blood platelets often begin to diminish in 

 number, the maximum reduction being usually observed after ten 

 to fifteen minutes and the number as a rule returning to normal 

 within half to one hour. The greatest reduction in blood 

 platelets was observed in cats, in two of which 85 per cent, and 

 90 per cent, of the platelets disappeared from the circulating 

 blood within ten and fifteen minutes respectively, and the count 

 again reached normal a half hour after the injection. 



3. Increasing amounts of free thromboplastic substance (cyto- 

 zyme) probably derived from platelets begin to appear in the 

 blood stream as the coagulation time becomes shortened. 



4. No changes in the content of the blood in the other factors 

 concerned in coagulation, such as calcium, fibrinogen or anti- 

 throntbin, are demonstrable. 



5. The increase in the thromboplastic agent cytozyme and the 

 shortening in coagulation time of the blood do not occur simul- 

 taneous with the numerical change in the platelets, but follow it. 

 The maximum shortening in coagulation time occurs some time 

 after the numbers of platelets have again returned to normal, 

 and persists for hours. 



6. The characteristic shortening of coagulation time after 

 intravenous injection of sodium citrate does not occur in animals 

 (ducks) in whose blood few or no platelets occur. In fact, if 

 sufficient citrate is administered, the opposite effect is accom- 

 plished in such animals and the coagulation time becomes mark- 

 edly prolonged. 



7. The shortening of coagulation time after intravenous 

 injection of sodium citrate likewise fails to occur in human 

 beings suffering from hemorrhagic blood diseases, in whose 



