H&MOLYSINS. 3 1 



This proved to be the case, the complement of 

 guinea-pig blood fulfilling the requirements. If 

 they added to the inactive normal dog serum about 

 2 c.c. normal guinea-pig serum, the haemolytic prop- 

 erty was restored and the guinea-pig red cells 

 dissolved completely. This can only be explained 

 by assuming that in guinea-pig blood there exists 

 a complement which happens to fit the hapto- 

 phore group of the second substance, or inter-body, 

 of the normal dog serum. This combination of 

 guinea-pig blood, inactive normal dog serum, 

 and a reactivating normal guinea-pig serum is the 

 best possible one to demonstrate the existence in 

 normal dog serum of an inter-body ; for the guinea- 

 pig serum should be the best possible preservative 

 for the guinea-pig red cells. The haemolysis fol- 

 lowing the addition of this serum shows positively 

 the existence of a substance in the dog serum 

 which has acted with something in the guinea-pig 

 serum.* 



Inter-body and Complement. We see, then, that 

 the haemolytic action of normal sera depends, just 



* Of such combinations, i.e., combinations in which a 

 complement derived from the same animal from which the 

 red cells are derived fits to the inter-body of other species 

 of animals, causing the solution of red cells of the latter, 

 Ehrlich and Morgenroth found still other examples. For 

 instance, guinea-pig blood, inactive calf serum, guinea-pig 

 serum; goat blood, inactive rabbit blood, goat serum; 

 sheep blood, inactive rabbit blood, sheep serum ; guinea-pig 

 blood, inactive sheep serum, guinea-pig serum. 



