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Fractional Withdrawal of Complement and Amboceptor by Means 



of Antigen. (Preliminary Note.) 

 By J. 0. Wakelin Barratt, M.D., D.Sc. Lond., Director of Cancer 



Research Laboratory, University of Liverpool (Mrs. Sutton Timmis 



Memorial). 



(Communicated by Prof. C. S. Sherrington, F.R.S. Received May 15, 1911.) 



The problem which forms the objective of the present investigation is 

 the determination of the extent to which complement and amboceptor are 

 withdrawn by amounts of antigen which are insufficient to cause complete 

 removal of these two substances. 



In this investigation the source of both complement and amboceptor 

 was normal human blood serum, which was employed alone when it was 

 desired to preserve the natural relationship of complement and amboceptor ; 

 when it was desired to vary this relation, artificial mixtures of complement 

 and amboceptor were prepared, which presented wide divergence from the 

 relation obtaining in normal serum. 



Human serum has a hemolytic action, not very considerable in degree, 

 upon the red blood cells of the rabbit, which were employed as antigen. 

 In all experiments made with this haemolytic system the same volume of 

 fluid was employed. Estimations of complement and amboceptor were 

 expressed in terms of the equivalent quantities of active and inactivated 

 normal serum respectively, it being found that the composition of healthy 

 sera ordinarily exhibited only slight variation, any marked change in the 

 content of these two substances being exceptional. 



The estimation of complement was sometimes made by determining the 

 maximum amount of red blood cells completely laked by a given quantity 

 of complement-holding fluid in the presence of a considerable excess of 

 amboceptor, and then ascertaining the amount of normal serum capable of 

 producing the same degree of haemolysis under similar conditions of 

 experiment. It was, however, sometimes found more convenient to keep 

 the amount of red blood cells employed constant, and to vary the con- 

 ditions of experiment until these were so adjusted that complete haemolysis 

 was observed at the end of a period of 90 minutes at a temperature of 

 '37° C. 



The estimation of the amount of amboceptor in serum was carried out 

 by first determining the amount of complement present and then ascer- 

 taining, in the absence of any addition of amboceptor, the hsemolytic power 



