176 ANTI-BACTERIAL PROPERTIES OF SERUM 



It is thus seen, in accordance with our previous results, 

 that practically all the normal opsonin is removed by these 

 various methods of treating the serum. To contrast with 

 this we give the results in the case of an immune serum. 



Opsonic count 

 Anti-staphylococcus serum from rabbit 



Fresh and unheated 12-3 



Heated one hour at 55 C 2-9 



Unheated and treated with red corpuscles + immune- 

 body 3-1 



Unheated and treated with serum precipitate . 3-5 

 Unheated and treated with emulsion of Staphylococcus 



aureus 0-7 



It is thus seen that 1 treating the serum with the sub- 

 stances which absorb complements has practically the same 

 effect on the serum as heating has ; there being approxi- 

 mately the same amount of immune opsonin left, the latter 

 being unaffected by the complement-absorbers. An emul- 

 sion of staphylococcus, however, removes the opsonin almost 

 entirely. 



Other confirmatory examples may be given : 



Treatment by Precipitate 



Opsonic count 

 Anti-staphylococcus serum 



Fresh and unheated 18-2 



Heated one hour at 55 C 6-9 



Unheated and treated with precipitate . . .5-8 



In this case there was an enormous excess of precipitate, 

 the actual bulk of the precipitate being three times that of 

 the serum ; there would, therefore, probably be some dilu- 

 tion of the serum. The treated serum has practically the 

 same opsonic value as the heated ; that is, in spite of the 

 large amount of absorber (precipitate) the immune opsonin 

 is unaffected. 



1 The methods of treating a given serum are the same as those described 

 by us in the previous section (p. 162). 



