BACTERICIDAL TEST-TUBE EXPERIMENTS. 



141 



in order to effect agglutination; thus Metchnikoff vibrios to 

 Metchnikoff immune serum, Xordhafen vibrios to Nordhafen 

 immune serum, etc. The mixtures were kept at 37 C. for one hour, 

 diluted to 25 cc. with salt solution (in order to dilute the serum as 

 much as possible), and then centrifuged. The fluids were poured 

 off; the sediments consisting of agglutinated bacteria were thoroughly 

 shaken, each with 2^ cc. inactive Metchnikoff immune serum and 

 allowed to stand for H to 2 hours at 37 C., the mixtures being occa- 

 sionally shaken. On then again centrifuging for a long time, I was 

 able to pour off a clear bacterial-free fluid which was used for the 

 following experiment (columns 2 to 5). 



TABLE V. 



Control I. -nj^ cc. bouillon culture + 2 cc. 0.85% salt solution=oo. 



" II. 0.1 cc. active guinea-pig serum +0.01 cc. inactive goat immune 

 serum against vibrio Metchnikoff + T^ViT cc - bouillon culture = 0. 

 " III. Sterility of all the sera = 0. 



This experiment shows that by previously adding dead bacteria 

 of the corresponding species and then using the centrifuged serum, 

 it is possible to remove the property by means of which an immune 

 serum when in excess can exert a complement-deflecting action. 

 This absorption, however, did not succeed with three other species 

 of bacteria. Hence we can conclude that the deflecting agent of 

 the immune serum is a substance produced by immunization and 



