PROPERTIES OF COMPLEMENTOIDS 49 



4. To each tube is added the standard amount of red corpuscles, 

 treated previously with 3 D of IB, and the tubes are placed in the 

 incubator for another hour. Haemolysis will, of course, take place 

 in the added corpuscles according to the amount of uncombined C 

 present in each tube. The tubes are then placed in a cool chamber 

 till next morning ; the red fluid in each tube is pipetted off, and 

 the amount of sedimented corpuscles left is estimated as above 

 described. 



In a control set of tubes complement only is added, and we thus 

 ascertain how much C is taken up when no Cd is present. It is then 

 seen how much C has been prevented from combining with the 

 R + IB molecules by means of a given amount of Cd. 



2. Complementoid combines with a serum + its anti- 

 serum, 1 and prevents the union of complement. 



If the ordinary action of such a combination is shown thus, 



S + anti-S + C j + O { ^ j Result = no lysis. 



then we may represent the effect of Cd by the following 

 scheme 



S + anti-S + Cd j + C 



/ T> ; 



O \ J-D i Result = partial lysis. 



The following are the details of such an experiment : 



Two series (A and B), of nine tubes, each containing 0-5 c.c. 

 salt solution. 



C of guinea-pig, M.H.D. = 0-03 c.c., Cd = the same serum 

 heated. Anti-S is the serum (heated at 57 C.) of a rabbit 

 injected with guinea-pig's serum. 



Series A. Each tube receives 0-1 c.c. anti-S and 

 0-1 c.c. Cd. 



1 This was stated in the original paper as * complementoid combines with 

 anti-complement, and prevents the union of the latter with complement ' 

 (vide p. 40). 



MTTIB IB 



