424 



Mr. H. R Dean. 



[Oct. 13, 



serum, which had been inactivated in the ordinary way by heating it for 

 half -an -hour at 56° C, was found to possess to a marked degree the property 

 of increasing agglutination. As far as agglutination was concerned, the 

 heated whole guinea-pig serum appeared to possess the same properties as 

 the saline solution of middle-piece. 



Table IV. — Comparison of Heated Whole Serum with the Middle-Piece 

 Fraction. 



The fresh guinea-pig serum was previously heated for half an hour at a 

 temperature of 56° C. 



| Dilutions. 



Heated whole serum. 



Middle-piece solution. 



1 



1—10 









1—20 



+ + + + 





3 



1—40 







4 



1—80 







5 



1—160 





+ + 



The two sets of dilutions were comparable, that is to say, the 1 in 10 dilution of middle-piece 

 solution corresponded to the amount of middle-piece in a 1 in 10 dilution of whole serum. 



To every tube was added a suspension of red cells and the diluted immune serum. It was 

 shown by appropriate controls that neither this dilution of immune serum, 1 in 200, nor the 

 heated whole serum, nor the middle-piece solution, in the dilutions employed, had the power of 

 ;i jighitinating the red cells. 



Influence of the End-Piece. 



Only a few experiments were carried out with a view to ascertaining the 

 influence of the end-piece fraction of the complement. In one case the 

 solution of end-piece had no influence on agglutination, acting either alone 

 or in conjunction with the middle-piece solution. Another end-piece 

 solution had a slight influence in a dilution of 1 in 10 in increasing the 

 agglutination of the red cells by an antiserum. When further diluted it 

 had no action. The same solution of end-piece somewhat increased the 

 agglutination produced by the interaction of antibody and middle-piece. 



It should be added that neither solution of end-piece had in the dilutions 

 employed the slightest agglutinative action on the red cells in the absence of 

 the specific immune body. The discrepancy between the two solutions 

 probably depended on slight differences in the method of separation. 



In any case, the substance which aids in agglutination appears to be 

 contained chiefly in the fraction of the globulin which is precipitated by 

 carbon dioxide. The agglutinating substance is present in whole normal 

 serum, but its agglutinative property can be conveniently studied in a 

 middle-piece solution, since the progress of agglutination is not interrupted 



