A Test for Antithrombin in the Blood. 39 



second stage of the latent period, in such wise that the reaction 

 with antigen produces a cellular stimulus, with muscular con- 

 traction in case of the uterus. It is for this reason, that the 

 combination of antigen and antibody in the blood never produces 

 an anaphylactic response. 



The "activation" by the cells also greatly increases the avidity 

 of cellular antibody for antigen, as has been shown in previous 

 papers. Exactly the same features differentiate cellular from 

 circulating antibodies after active sensitization. 



23 (955) 



A test for antithrombin in the blood. 

 By Alfred F. Hess, M.D. 



[From the Research Laboratory, Board of Health, New York City.] 



The method of testing for antithrombin in the blood is at 

 present very difficult, as it requires the preparation of a pure 

 fibrinogen containing no prothrombin, that is to say, which does 

 not clot upon the addition of calcium, and also the preparation 

 af a pure thrombin which can be made from fibrin. As a result 

 the method is hardly adaptable to general clinical use. 



For some time I have employed a method which seems to 

 meet this difficulty. For this purpose about 9 c.c. of blood are 

 aspirated and put into 1 c.c. of 1 per cent, sodium oxalate. The 

 blood is centrifugalized and the plasma siphoned off in the usual 

 way. The plasma is then recalcified by adding 2, 3, 4 and 5 

 drops respectively of a X P er cent, calcium chloride solution. 

 In this way we ascertain the general coagulability of the plasma 

 which is the composite of a number of factors, — prothrombin, 

 fibrinogen and antithrombin, and we determine the optimal 

 amount of calcium for this particular plasma. If we heat some of 

 this plasma to 6o° C, the prothrombin, as is well known, is de- 

 stroyed and the fibrinogen is coagulated. After filtering off this 

 :oagulum, we have a plasma which contains antithrombin. The 

 strength of this antithrombin may be ascertained for clinical 

 purposes as follows: 



