MODE OF ACTION OF BACTERICIDAL SERA 



123 



is due only to the serum's 4 content of immune body is shown by the 

 following experiment in which inactive immune serum is compared 

 with inactive normal serum of the same species, both sera being 

 complemented with active normal serum. 



TABLE II. 



Control I. ^nnr cc - bouillon culture + 2 cc. 0.85% salt sol. +3 drops of 



bouillon, planted as above, result oo. 

 " II. Sterility of the immune serum, 0. 

 " III. " " " inactive normal rabbit-serum, 0. 

 " IV. " " " active normal rabbit-serum, 0. 

 All the tubes made up to equal volumes with 0.8.5% salt solution, then 

 placed into a thermostat at 37 C. for three hours. Finally, five drops of each 

 specimen plated on agar. 



This experiment, too, shows that Vie cc. immune serum plus 

 1 cc. or 1 / 3 cc. normal active rabbit serum kills the germs completely; 

 while larger doses of the immune serum are less effective. The addi- 

 tion of normal inactive rabbit serum has no effect. 



The same phenomenon can be demonstrated in another man- 

 ner. For the complementing serum any active serum is used which 

 by itself already possesses a slight destructive action. If to such a 

 serum varying amounts of an inactive immune serum are added, 

 it will at times be found that small quantities of the latter increase 



