170 ANTI-BACTERIAL PROPERTIES OF SERUM 



It is thus brought out that a bacterium combined with the 

 homologous immune-body absorbs or fixes bactericidal com- 

 plement, hsemolytic complement, and normal opsonin alike. 

 We have never been able to obtain a diminution of one of 

 these without the other two being similarly affected, though 

 further observations will be necessary before a general 

 statement can be made. It is to be noted that these results 

 are obtained with powerful complement-absorbers. When 

 small quantities of bacterial emulsions are used there may 

 be a much greater diminution in bactericidal than in 

 haemolytic action (p. 202). 



It will be noticed on comparing the results in the above 

 tables that there is remarkable similarity in the variation 

 of the haemolytic action and of opsonic actions, produced 

 by the methods used. Diminution in the opsonic effect 

 associated with moderate fall in haemolytic power is best 

 seen when the opsonic index of the normal serum comes out 

 low. This is in accordance with what is seen on diluting a 

 normal serum with high opsonic power, the effects of further 

 diluting being most marked after the opsonic index has been 

 reduced somewhat by previous dilutions. 



GENERAL RESULTS 



We have thus tested the three chief varieties of immune- 

 bodies (' amboceptors '), namely, those obtained by the 

 injection of (a) red corpuscles, (b) serum, and (c) bacteria, 

 respectively, and have found that in each case the combina- 

 tion of receptor + immune-body removes the opsonin of 

 normal serum as tested by an emulsion of Staphylococcus 

 aureus. We have also shown that a bacterium treated with 

 immune-body takes up more of the normal opsonin than 

 the same bacterium untreated, just as it takes up more of 

 the normal complement as tested by haemolysis. If we 

 define a complement from the chemical point of view as 

 above explained, it is evident that the thermolabile opsonins 



