42 PROPERTIES OF ELEMOLYTIC SERA 



red corpuscles as rabbit's complement does ; in other words, 

 as to whether these two complements from different species- 

 of animals possess similar haptophore groups. 



As is well known, ox's corpuscles, treated with immune- 

 body from the rabbit, are lysed on the addition either of 

 guinea-pig's complement or of rabbit's complement. This 

 would point to the haptophore groups of the two comple- 

 ments being the same. Ehrlich and Morgenroth have 

 supposed in the corresponding case of the immune-body 

 to rabbit's corpuscles obtained from the guinea-pig, that 

 there are really two immune-bodies present, one of which 

 combines with the rabbit's complement and one with the 

 guinea-pig's, and point out in favour of this view that when 

 rabbit's complement is used, the minimum haemolytic 

 dose of immune-body is about ten times greater than 

 when guinea-pig's complement is used. We have accord- 

 ingly investigated the case of the immune-body obtained 

 by injecting the rabbit with ox's corpuscles. As both 

 rabbit's and guinea-pig's complements are taken up by 

 ox's corpuscles combined with immune-body, the question 

 comes to be whether both complements combine with the 

 same molecules. Does the combination of guinea-pig's com- 

 plement prevent the combination of rabbit's complement 

 and vice versa ? We have conducted a large number of 

 experiments of this nature, and the result has always been 

 to give an answer in the affirmative. The experiments are 

 on the same lines as those already described. Suppose we 

 wish to test how much guinea-pig's complement is kept 

 from combination by the previous combination of a given 

 amount of rabbit's complement. To one series (A) of tubes, 

 each containing the test amount of corpuscles combined with 

 the same amount of IB (generally 3-4 doses), we add increas- 

 ing amounts of guinea-pig's complement and test how much 

 the treated corpuscles will take up. In another series (B) 

 of similar tubes, we add a given amount of rabbit's C, allow 



