COMPLEMEXTIBIL1TY OF THE AMBOCEPTORS. 239 



all of the completions of normal amboceptors succeeded, we found 

 in Frankfurt that we obtained negative results in the great majority 

 of the experiments. The complements necessary for the completion 

 of almost all normal amboceptors were absent, while complements 

 were present for a certain normal amboceptor (guinea-pig blood, ox 

 serum), and for one obtained by immunizing a goat with sheep blood. 1 



This behavior indicates clearly enough a plurality of the comple- 

 ments in a serum, and we do not doubt that further investigations 

 will show the same to be true for the partial complements of other 

 sera. The occasional absence of one or the other- complement will 

 most easily be discovered just in the completion of normal amboceptors, 

 for here but few amboceptors have to be considered. Of the numerous 

 amboceptors produced by immunization in many cases, at least a few 

 will find fitting dominant complements. According to our observa- 

 tions, conclusions can be drawn only with the greatest care from 

 isolated negative completion experiments. One cannot conclude that 

 an amboceptor is absent from the impossibility to reactivate normal 

 inactive sera by means of several other active sera. 



For the evaluation of bactericidal sera in animal experiments 

 we believe it to be especially important to consider cases of this 

 kind. The entire absence or a marked diminution of complements 2 ' 

 which functionate as dominant complements for certain bactericidal 

 amboceptors may lead to a disturbance in the regularity of a series 

 of experiments, disturbances which show themselves in the fact that 

 now and then an animal dies of the infection even though in the zone 

 of sufficient immune serum to protect the animal. Such irregularities 

 are quite common in the usual test series and manifest themselves 

 frequently in the evaluation of bactericidal sera, where they then are 

 very disturbing. 



1 In respect to its complements horse serum occupies a special place among 

 most other sera used in the laboratory. Thus, for example, we were rarely 

 successful in complementing the amboceptor of a rabbit immunized with ox 

 blood; we never found a complement in horse sera for the amboceptors of geese 

 or goats immunized with ox blood. That the locality plays a certain role in 

 these phenomena follows from our observations that here, in contrast to the 

 statements of so reliable an observer as P. Miiller in Graz, rabbit blood is not 

 dissolved by duck serum to any appreciable extent. 



2 Another abnormal phenomenon which is often observed in this connec- 

 tion, the disturbing action of large amounts of the immune serum, is explained 

 by the peculiar deflection of complements by an excess of amboceptor, as 

 has been determined by M. Neisser and Wechsberg (see pages 120 et seq ). 



