UNION OF COMPLEMENT 27 



sociation of complement ; that is, a late lysis occurring in 

 the test corpuscles after time has been allowed for the 

 combination of complement with the serum + anti-serum. 

 This is the case with the absorption of guinea-pig's comple- 

 ment by guinea-pig's serum with anti-serum from the rabbit, 

 and is referred to in our original paper as a ' weak combina- 

 tion of complement with anti-complement '. Here again 

 the possibility of there being weakly acting complement 

 molecules, which are not taken up by the serum + anti- 

 serum, cannot be entirely excluded, but the probability 

 appears to be that there is some dissociation of complement. 

 Unequivocal proof of the dissociation of complement could 

 only be supplied if we could recover complement from cells, 

 bacteria, precipitates, &c., with which it had combined, 

 after these were repeatedly washed and centrifugalized, 

 and this we have not yet succeeded in doing. The firmness 

 of union of complement or the fixation of complement in 

 most cases is of the greatest importance in serum researches, 

 and really constitutes the basis of a number of the methods 

 employed. No absolute statement can be made, however, 

 and the behaviour of complement must be studied in con- 

 nexion with any particular combination under consideration. 



THE AMOUNT OF COMPLEMENT ABSORBED THROUGH THE 

 MEDIUM OF IMMUNE-BODY 



We have now to consider the exact amount of comple- 

 ment which is taken up in proportion to the amount of 

 immune-body combined with the red corpuscles. For any 

 given amount of immune-body a series of test-tubes, con- 

 veniently about nine, is taken ; each tube contains 1 c.c. 

 of suspension of red corpuscles along with the stated amount 

 of immune-body ; to the several tubes we add gradually 

 increasing amounts of complement. (We can judge by 

 experience what is the likely amount of complement to be 

 taken up, and arrange the amounts so that in the first 



