BACILLI OF THE COLON-TYPHOID-DYSENTERY GROUP 661 



is followed by a tissue reaction (a part of which is evident as antibody 

 production) so rapid that the protective processes are developed with 

 sufficient potency to check the infection before it has reached a phase at 

 which symptoms become apparent. 



Bactericidal and Bacteriolytic Substances. The bacteriolytic sub- 

 stances in typhoid-immune serum may be demonstrated either by the 

 intraperitoneal technique of Pfeiffer or in vitro. In the former experi- 

 ment a small quantity of a fresh culture of typhoid bacilli is mixed 

 with the diluted immune serum and the emulsion injected into the 

 peritoneal cavity of a guinea-pig. Removal of peritoneal exudate with 

 a capillary pipette and examination in the hanging drop will reveal, 

 within a short time, a swelling and granulation of the bacteria the 

 so-called Pfeiffer phenomenon. The test in vitro, as recommended by 

 Stern and Korte, 58 may be carried out by adding definite quantities of 

 a fresh agar culture of typhoid bacilli to progressively increasing dilu- 

 tions of inactivated immune serum together with definite quantities 

 of complement in the form of fresh normal rabbit or guinea-pig serum. 

 At the end of several hours' incubation at 37.5 C. definite quantities 

 of the fluid from the various tubes are inoculated into melted agar 

 and plates are poured to determine the bactericidal action. Careful 

 colony counting in these plates and comparison with proper controls 

 will not only definitely demonstrate the presence of bactericidal sub- 

 stances in the immune serum, but will furnish a reasonably accurate 

 quantitative estimation. (For technic of these tests see page 307.) 



Although normal human serum contains in small quantity sub- 

 stances bactericidal to typhoid bacilli, moderate dilution, 1 : 10 or 

 1 : 20, of such serum will usually suffice to eliminate any appreciable 

 bactericidal action. The bactericidal powers of immune serum, on the 

 other hand, are often active, according to Stern and Korte, in dilutions 

 of over 1 : 4000. The specificity of such reactions gives them a con- 

 siderable degree of practical value, both in the biological identification 

 of a suspected typhoid bacillus in known serum and in the diagnosis 

 of typhoid fever in the human patient by the action of the patient's 

 serum on known typhoid bacilli. In the publication of Stern and 

 Korte, quoted above, it was found that typhoid patients during the 

 second week often possess a bactericidal power exceeding 1 : 1000, 

 whereas the blood of normal human beings was rarely active in 

 dilutions exceeding 1 : 50 or 1: 100. While scientifically accurate 

 the practical application of bactericidal determinations for diagnosis 



58 Stem und Korte, Berl. klin. Woch., x., 1904. 



