OPSONIC ACTION 161 



may take up haemolytic complement, and a haemolytic 

 receptor -f immune-body may take up bactericidal comple- 

 ment. This statement may be made in a general sense 

 without implying that there may not be multiple comple- 

 ments in a serum ; on the contrary, we know that some 

 complements may not be taken up. So far as the general 

 laws of chemical combination in immunity are concerned, 

 the distinguishing property of complement is that it is 

 absorbed or fixed through the medium of an immune-body ; 

 whether it produces a bactericidal, haemolytic, &c., effect 

 or not, is in a sense accidental, depending on the suscep- 

 tibility of the cell to the zymotoxic group. It may be of 

 interest to recall the instance recorded above, in which an 

 agglutinating effect was produced by ' complement ' in this 

 sense. Do the thermolabile opsonins of normal serum 

 belong to the group of complements, or do they conform 

 to anti-substances with specific combining affinity ? In the 

 present paper we leave out of consideration the opsonic 

 substances which can be demonstrated in a heated immune 

 serum and the small residuum which may be present in 

 a heated normal serum. We simply determine what effects 

 on the opsonic power of normal serum are produced by 

 certain methods of absorption which lead to the fixation of 

 hsemolytic and bacteriolytic complements. To what extent 

 is the opsonic action of the serum reduced by these absorp- 

 tive methods, as compared with the effect of heating the 

 serum at 55 C. ? 



In investigating the question as to the absorption of 

 opsonins we have used the immune-bodies corresponding 

 to the receptors of (a) red corpuscles, (b) blood serum, and 

 (c) bacteria. The results are shewn in the three following 

 sections. 



MUIR 



