60 COLLECTED STUDIES IN IMMUNITY. 



the serum was filtered, the filtrate showed the same solvent power 

 for guinea-pig blood, whereas the solvent power for rabbit blood 

 had almost entirely disappeared, for 0.8 cc. effected only a trace of 

 solution and 0.23 cc. none at all. This loss of solvent power could 

 be due only to an absorption, by the filter, of (1) the interbody 

 fitting the rabbit blood, or (2) the complement, or (3) both. Since, 

 however, the solvent action of the filtrate on rabbit blood was restored 

 by the addition of complement-containing horse serum, while the 

 addition of interbody had no effect, it follows that the filtration 

 had removed only the complement. From this fact, namely that 

 a serum may be deprived of its complement for rabbit blood while 

 the complement for guinea-pig blood remains, we must conclude 

 that there are two different complements corresponding to these two 

 interbodies. According to this, then, at least four different substances 

 are concerned in the case in question, two different immune bodies 

 and two complements fitting thereto. One pair of these acts on 

 guinea-pig blood and the other on rabbit blood. According to 

 Buchner only one single substance, the alexin of goat serum, would 

 be concerned. Further details of these experiments will be published 

 later. We should, however, like to observe that in the horse serum 

 used for reactivating, it was possible to prove the existence of two 

 complements. This proof, moreover, was effected in two ways, 

 by means of filtration and by the production of anticomplements. 

 The following observation will show that a still greater multi- 

 plicity of normal haemolysins can exist in the serum. In our second 

 communication we have given a detailed description of an experi- 

 ment in which a normal interbody of dog serum was caused to 

 combine with guinea-pig blood and then reactivated by means of 

 guinea-pig scrum, which served to supply the complement. In this 

 experiment the interbody contained in 0.2 cc. dog serum was bound 

 by a certain quantity of guinea-pig blood-cells. This is the amount 

 of dog serum which, when active, just suffices to completely dissolve 

 the given quantity of blood. On repeating this experiment, but 

 employing horse serum as complement, it was found impossible to 

 reactivate the dose of interbody just sufficient for solution (0.2 cc.). 

 By systematic trials, in which multiples of the dose of interbody 

 previously used were employed, we finally determined that it required 

 six times the amount, i.e., 1.2 cc., in order that the interbody would 

 bo completely reactivated by the horse serum. That is, the first- 

 employed dose of the inactive dog serum, which contained just sufficient 



