182 ANTI-BACTERIAL PROPERTIES OF SERUM 



complement, viz. rabbit's corpuscles treated with immune- 

 body, it loses also its hsemolytic action on pigeon's cor- 

 puscles. And it has been shown in the previous section that 

 an emulsion of a bacterium treated with immune-body 

 absorbs more opsonin than the untreated emulsion, the 

 amount of opsonin left being practically the same as 

 when the serum is heated. The following is an additional 

 example : 



Opsonic Action of Normal Human Serum on the 



Tubercle Bacillus 



Opsonic count 



Normal serum unheated 6-5 



heated at 55 C. . . . . . . 0-2 



treated with emulsion of V. Metchnikovi + 



immune-body 0-19 



III. THE RELATIONS OF THE OPSONIN OF AN IMMUNE SERUM 



Our results, as above detailed, show that the opsonin of 

 the anti-staphylococcus serum corresponds as regards 

 specificity and combining relationships with true anti- 

 substances developed in the process of immunization. Does 

 it correspond with the type of an immune-body or of an 

 agglutinin ? Does it in combination with its corresponding 

 receptor lead to the absorption of complement, or does it 

 not ? In the first place, it is certain that every immune- 

 body does not produce an opsonic effect. We have an 

 anti-coli serum, for example, which contains immune-body 

 in considerable quantity, but it has no opsonic effect. 

 A given amount of emulsion of the B. coli alone was found 

 to take up 0-04 c.c. of guinea-pig's complement, while the 

 same amount of emulsion treated with the anti-serum took 

 up 0-12 c.c., the absorption of complement being tested by 

 the usual haemolytic methods. In the case of the anti- 

 staphylococcic serum the amount of immune-body appeared 

 to be considerably less. The sample with the greatest 



