FURTHER STUDIES ON THE DYSENTERY BACILLUS. 317 



tion of complement described is actually due to an excess of im- 

 mune body and not, for example, to the presence of an anticomple- 

 ment. 



Prof. Neisser and I thought that this phenomenon of comple- 

 ment deflection could be utilized in another direction. Ehrlich and 

 his pupils, it will be remembered, have demonstrated the existence 

 of a plurality of complements. In view of this it was conceivable 

 that, following a large addition of inactive immune serum to a normal 

 serum bactericidal per se, only that complement would be deflected 

 which is able to complement the immune serum, while the remaining 

 complements were left unaffected. From this it would follow that 

 the normal active serum in question would in the main have lost 

 only this one bactericidal action, while it still retained almost all the 

 others. One would thus have a serum which had lost a bactericidal 

 action chiefly for that bacterium whose immune body has been added 

 in excess; that is to say, a truly specific nutrient medium. Proceeding 

 from these considerations we first infected a normal stool with a 

 small quantity of dysentery bacilli. To small amounts of this infected 

 stool 2.0 cc. normal active goat serum and 0.2 cc. inactive immune 

 serum were added and the mixture kept in the thermostat. At the 

 end of three hours six drops of this mixture were added to a second 

 tube containing 2.0 cc. normal active goat serum and 0.2 inactive 

 immune serum. Agar plates were made (1) from the original infected 

 stool; (2) from the first tube; (3) and from the second tube after it 

 also had been kept at 37 C. for three hours. A great many tests 

 showed that a specific enriching in dysentery bacilli takes place, so 

 that when the first plate shows only a few scattered colonies of dysen- 

 tery bacilli, Plates II and III show numerous colonies. In one case 

 we even succeeded in finding dysentery bacilli in Plates II and III, 

 although none had been found on Plate I. It may be mentioned 

 that we used the agar medium recommended by v. Drigalski and 

 Conradi l for the diagnosis of typhoid bacilli, and found it of great 

 advantage. The method just described for enriching cultures may 

 perhaps be extended and perfected. 



1 Zeitschrift fur Hygiene, Vol. XXXIX. 



