PATHOGENIC BACTERIA. 117 



Carbolized Gelatine Gelatine which has added to it ^ per 

 cent, carbolic acid will allow the typhoid bacillus to develop, 

 other similar bacilli being destroyed. 



Glucose Gelatine. In glucose gelatine there is no gas-produc- 

 tion. Indol is likewise not generated by the typhoid bacillus, 

 whereas it is by the colon bacillus. On Eisner's potato-gelatine 

 the colon bacillus and the typhoid bacillus grow readily. The 

 medium of Hiss is of great assistance in isolating the germ. 



FIG. 61. 



The Widal agglutination reaction (Slater and Spitta). 



The Gruber- Widal blood-serum test, or, as otherwise known, the 

 agglutination-phenomenon (Fig. 61), has the following history: 



About 1889, Charrin and Roger observed in the serum of im- 

 munized animals that the B. pyocyaneus arranged itself in little 

 clumps. Other investigators reported the same thing for other 

 bacteria, and Metschnikoff added that motility was destroyed. 



In 1895, Bordet showed that the serum of cholera-immunized 

 animals, when mixed with bouillon cultures of cholera spirilla, 

 affected their motility and caused them to form masses, or 

 " Klumpen," as the Germans call it- 



R. Pfeiffer, in the same year, showed that the introduction of 

 immune serum at the same time with virulent cholera spirilla 



