PROPERTIES OF COMPLEMENTOIDS 69 



pig's serum than when it is guinea-pig's serum 55. In 

 other words, the serum 55 exerts a strong inhibitory in- 

 fluence on lysis, which is not the case when the complement 

 is removed from the serum instead of being changed into 

 complementoid. The dose in guinea-pig's ' treated serum ' 

 is in fact little, if at all, greater than that in ox's serum 55. 

 The high dose of complement necessary when serum 55 

 is used as the medium of suspension was supposed by us 

 to be due to complementoid, and this view is fully confirmed 

 by the results of using as the medium of suspension the serum 

 deprived of its complementoid. We are thus justified in 

 concluding that the presence of a large amount of comple- 

 mentoid interferes with the action of complement and thus 

 raises the haemolytic dose. 



These results are of importance in connexion with the 

 question as to the existence of complementoids and their 

 combining properties, and constitute an amplification and con- 

 firmation of what has been stated in the preceding section. 

 Gay l in a recent paper criticizes the well-known experiment 

 of Ehrlich and Sachs 2 in which the complementoid of dog's 

 serum prevents the action of guinea-pig's complement on 

 guinea-pig's corpuscles sensitized with the natural immune- 

 body in the dog's serum, and comes to the conclusion that 

 the supposed complementoid is merely an attenuated com- 

 plement attenuated both as regards its combining affinity 

 and its toxic action. We would point out, however, that 

 in our former experiments, as in the present case, the serum 

 heated at 55 C. is quite devoid of haemolytic action ; in fact, 

 so far as can be seen from the haemolytic action, the com- 

 plement has entirely disappeared. Nevertheless, in such 

 a serum, a substance (complementoid) is present which 



1 Gay, Centralbl. /. Bakteriol. u. Parasitenk., 1. Abt., Originale, Bd. xxxix, 

 S. 172. 



1 Ehrlich and Sachs, Berlin, klin. Wochenschr., 1902, No. 21. In a recent 

 paper, Centralbl. f. BakterioL, 1. Abt., Originale, Bd. xl, S. 125, Sachs has 

 replied to Gay's objection and confirmed his previous results. 



