MULTIPLICITY OF ANTIBODIES IN NORMAL SERUM. 589 



of two parts, which Ehrlich terms interbody and complement 

 respectively. The interbody combines with the erythrocyte on the 

 one hand, and with the active dissolving agent, the complement, 

 011 the other. The experiments just described, therefore, demon- 

 strated merely the plurality of the interbodies, and shed no light 

 on the unity or plurality of the complements. In fact it was 

 easily conceivable that a single complement (the alexin of Buchner 

 and Bordet) fitted to both interbodies and effected the solution 

 of both species of erythrocytes. Ehrlich and Morgenroth, however, 

 were able to demonstrate that the complements concerned were 

 different. They filtered a serum through Pukall filters, and so 

 effected a separation of the two, one of the complements passing 

 through completely, while all but traces of the other were held 

 back. It was thus shown that the hsemolytic " power " of the normal 

 goat serum against rabbit and guinea-pig blood was due to at 

 least four distinct substances existing independently in the serum 

 side by side. 



Nuttall d7) was able to show that normal rabbit blood was 

 bactericidal for B. anthrax, B. subtilis, and Bact. megatherium; 

 Nissen d6) demonstrated the bactericidal power of rabbit blood 

 on cholera and typhoid bacilli, and on coccus aquatilis, and 

 Buchner w found that cell-free blood serum of rabbits acted 

 on anthrax, erysipelas of swine, typhoid bacilli, cholera, etc. 

 There is considerable variation in the action of the serum, on 

 different bacteria. Thus Nuttall found that rabbit blood acted 

 on anthrax bacilli, but not on staphylococcus aureus. On the 

 other hand, different sera behave differently on the same species 

 of bacterium. Thus Buchner found ox and horse serum without 

 effect on typhoid bacilli. The question again arises, whether the 

 bactericidal action of normal sera is due to a single substance or 

 to different substances. 



Experiments to decide this question were made by Nissen d6), 

 although it must be admitted that they were not entirely conclusive. 

 He injected a rabbit intravenously with large quantities of the 

 coccus aquatalis and observed that the blood obtained immediately 

 after had lost its bactericidal power for this coccus, while the 

 bactericidal power for cholera and typhoid bacilli remained 

 unchanged. 



Extensive investigations concerning this point were then made 

 by Bail d) who employed the absorption test. He found on 



