VARIATIONS IN TYPHOID BACILLI 



317 



Both Cohen S and Cohen B cultures were suspended in sterile 

 distilled water. Then 0.5 cc. of each of the above solutions and 

 0.5 cc. of bacterial suspension were put in small test tubes and 

 the results recorded after two hours incubation at 37°C. 



This experiment shows that cultivation in serum has rendered 

 the Cohen strain inagglutinable in an H-ion concentration which 

 agglutinates the normal strain. In this test Cohen S resembles 

 Bact. coll, but other tests (sugar fermentation) showed it to be 

 an absolutely typical typhoid bacillus. 



Similar tests were made with an inorganic acid, as follows : 



HCl agglutination 



Suspensions of both strains (Cohen S and Cohen B) were 

 made in sterile water. From normal hydrochloric acid solutions 

 in the following table were prepared by adding sterile water, 

 0.5 cc. of bacterial suspension, and 0.5 cc. of each acid solution 

 were mixed in small test tubes and incubated at 37° for two hours, 

 then stood in the ice chest overnight. The results were then 

 noted. 



The table below shows the final dilution of hydrochloric acid 

 in the combination of acid and bacterial suspension : 



