38 PROPERTIES OF H^EMOLYTIC SERA 



When a sub-haemolytic dose of immune-body is present 

 along with excess of complement, lysis should progress to 

 some extent after the usual time necessary for the union of 

 complement ; that is, some of the immune-body molecules 

 which have led to the union of complement should become 

 dissociated, and attach themselves to other receptors, 

 increased union of complement and increased lysis thus 

 resulting. On the other hand, with a sub-haemolytic dose 

 of complement lysis should have practically reached its 

 maximum after the time stated, all the complement present 

 having become fixed. As a matter of fact, this is what 

 happens in the case studied, namely, immune-body rabbit 

 v. ox along with guinea-pig's complement. We take a series 

 of tubes, each containing the standard amount of cor- 

 puscles, and add to the several tubes increasing fractions 

 of immune-body up to a little more than the hsemolytic 

 dose, along with excess of complement in each tube ; if we 

 then observe the amount of lysis after one and a half hours' 

 incubation at 37 C., and again after the tubes have been 

 kept for eighteen hours longer in a cool chamber at about 

 12 C., we find that in the latter case lysis has progressed 

 considerably, complete lysis occurring with about two-thirds 

 of the amount of immune-body which produced complete lysis 

 after incubation. On the other hand, if we use comple- 

 ment in the same way with excess of immune-body, we find 

 that there is scarcely any difference between the lysis in the 

 two cases ; there is some increase after eighteen hours, but 

 it is of quite a trifling nature. This result also appears to 

 distinctly support the view that molecules of immune-body 

 may dissociate after they have led to the union of com- 

 plement. There seems to be only one other explanation of 

 the results obtained, namely, that complement by itself can 

 act on partially damaged corpuscles, but we have no evidence 

 in support of such a supposition. 



