1911.] 



On the Factors Concerned in Agglutination. 



433 



globulin solution of guinea-pig serum a turbidity appears. Now this globulin 

 solution contains the middle-piece fraction of guinea-pig complement, the 

 fraction which is known to disappear in a complement-fixation experiment. 

 It is proposed, therefore, to make these questions the subject of further 

 investigation. 



Summary. 



(1) Sheep corpuscles are, as is well known, agglutinated by an homologous 

 antiserum. If, to a mixture of corpuscles with antiserum so dilute that no 

 agglutination is visible, there be added a solution of globulin obtained from 

 normal guinea-pig serum, the corpuscles are markedly agglutinated. By the 

 use of suitable controls it can be demonstrated that neither the globulin 

 solution nor the dilution of antiserum employed are of themselves capable of 

 agglutinating the corpuscles. 



(2) The substance present in the globulin solution which aids agglutina- 

 tion is relatively thermostable, and its presence can be demonstrated in whole 

 heated guinea-pig serum. 



(3) Corpuscles which have been sensitised and washed to remove free anti- 

 body can be agglutinated by the globulin solution. If, after agglutination has 

 taken place, the corpuscles be removed with a centrifuge, the supernatant 

 fluid can be shown to have lost its agglutinating property. 



(4) The agglutinating power of an extremely dilute antityphoid serum can 

 be increased by the addition of the globulin solution. By the addition of 

 globulin solution to a mixture of emulsion of B. typhosus with a dilution of 

 antiserum which is too weak by itself to agglutinate the bacilli, distinct 

 agglutination can be obtained. 



(5) The formation of a specific precipitate by the interaction of a serum 

 with its homologous antiserum depends, as is well known, on the presence, in 

 the mixture of a relatively large amount of the antiserum. If, to a mixture 

 of serum with antiserum so diluted that it is no longer able to produce a 

 precipitate, is added the globulin solution, a definite turbidity is produced. 



(6) It seems probable that an agglutinating serum (antiserum) contains 

 two factors, both of which are necessary to produce agglutination. The one 

 of these is the specific antibody, the other is a non-specific substance which 

 is possibly serum globulin. The interaction of antigen with antibody produces 

 an aggregation of the molecules of the non-specific substance which may 

 ultimately result in the formation of a definite turbidity. This process of 

 aggregation of the particles of the non-specific substance is an essential part 

 of the process of agglutination. It is possible to make a dilution of an anti- 

 serum which contains sufficient of the spesific anti-substance but not sufficient 



