The Influence of Salt- Concentration on Haemolysis. 407 



therefore, that the presence of the red cells prevents the action of the salt- 

 free medium on the complementary serum from progressing beyond a 

 certain point. Experiments carried out to test the hypothesis that this 

 might be due to a combination of the mid-piece with the red cells gave no 

 definite results, for reasons which need not be entered into here. 



The fact remains that those complementary sera which are unaffected by 

 simple dilution with salt-free saccharose solution at 0° C. show no evidence 

 of any absorption of the complement by red cells at this temperature. We 

 are, therefore, justified in saying that complement, combining directly with 

 red cells "in a salt-free medium, behaves in the same manner as complement 

 combining with red cells in a medium of normal saline solution under the 

 influence of a haemolytic antibody, in that no combination occurs at a 

 temperature of 0° C. 



In the experiments described above, and in the discussion of the results 

 obtained, the terms " complement " and " hemolytic antibody " have been 

 employed in their usually accepted sense. It is obvious, however, that 

 the sera employed contain many other substances, and the recent cross- 

 absorption experiments of Thiele and Embleton show that a hard and fast 

 division into complement and antibody is not permissible. It is, therefore, 

 possible that not the whole complement, but only some specialised part of it 

 can combine, unaided, with red cells in the absence of electrolytes ; but 

 this consideration does not affect the main thesis that a combination, that is 

 impossible in a salt-containing solution without the addition of a special 

 antibody, can occur in its absence in a salt-free medium. 



Conclusions. 



In the case of the hemolysis of sheep corpuscles by guinea-pig comple- 

 ment, it is found that : — 



1. The presence of an excess of an electrolyte (sodium chloride) above the 

 normal limit in a haemolytic mixture prevents the combination of the com- 

 plement with the red-cell-antibody complex. 



2. If the concentration of the antibody be markedly increased, it is possible, 

 up to a certain point, to counteract the effect of the increased salt concen- 

 tration. 



3. If the salt concentration be decreased, a decreasing concentration of 

 antibody serves to produce the union of red cells and complement. 



4. In an almost completely salt-free medium the combination occurs in 

 the complete absence of antibody. 



