OPSONIC ACTION 175 



serum, giving in each instance for comparison the effects on 

 normal opsonins under the same conditions of experiment. 

 We have made use of two samples of anti-staphylococcic 

 serum. One of these was kindly given to us by Dr. Dean, 

 for which we have pleasure in recording our indebtedness, 

 whilst the other was obtained by us from a rabbit by re- 

 peated intravenous injections of dead cultures of Staphy- 

 lococcus aureus. As it was employed at various stages in 

 the process of immunization, the degree of the opsonic effect 

 varies considerably in the different experiments. We may 

 state that heating for several hours at 55 C. appears to 

 have no appreciable effect on the thermostable immune 

 opsonin. The serum thus contrasts very markedly with 

 the normal rabbit's serum, the opsonic effect of which is 

 practically destroyed by heating for an hour at 55 C. 



I. THE EFFECTS OF ABSORBERS OF COMPLEMENT ON 



NORMAL AND IMMUNE OPSONINS 



We have tested whether or not the three combinations 

 of receptors + immune-body used in the previous experi- 

 mentsXp. 161) absorb the opsonin of the immune serum. 



The two following experiments bring out at a glance the 



. differences in the effects of treating a normal and an immune 



serum in various ways, each serum being afterwards tested 



on an emulsion of the Staphylococcus aureus in the usual 



way: 



Normal serum of rabbit Opsonic count x 



Fresh and untreated 18-1 



Heated one hour at 55 C 0-6 



Unheated and treated with red corpuscles + immune- 

 body 0-7 



Unheated and treated with serum precipitate . . 1-0 

 Unheated and treated with emulsion of Staphylococcus 



aureus 0-7 



1 This, of course, means the average number of cocci ingested per 

 polymorphonuclear leucocyte in Wright's technique. The observations 

 given in each table were of course carried out at the same time. 



