THE COLON, TYPHOID AND DYSENTERY BACILLI 3 S3 



iag^ the various types of bacteria in this group. Thus, in a 

 broth containing maltose, B. typhosus produces acid, B.coU 

 produces acid and gas, and B. dysenterim produces neither. 

 Specific agglutination with the serum of an animal" immunized 

 with a known culture constitutes the most important test in the 

 identification of unknown forms falling within this group. This 

 test may be used with the capsulated* species after they have 

 lost the tendency to form capsules through propagation on artifi- 

 cial media. ^ For a detailed discussion of the classifiration and 

 fermentative reactions of the colon-typhoid group reference may 

 be had to the paper of Winslow,' Kligler and Rothberg, with 

 which is included an extensive bibliography. 



' Hiss has devised a very useful medium for this purpose which obviates the neces- 

 sity of using the fermentation tube to detect the gas. His serum-water medium is 

 made by mixing beef serum, i part, with distilled -water, 2 to 3 parts, and steaming 

 IS minutes to destroy enzymes. , Pure litmus solution (about i part of a 5 per cent 

 solution to 100 parts of the medium) is then added to prgduce a deep blue color. 

 The medium is divided into several portions and i per cent of the desired carbo- 

 hydrate is added to its respective portion. The sugar serum-water media are then 

 sterilized at 100° C, on three days. Fermentation is shown not only by the redden- 

 ing of the litmus but also by coagulation of the liquid medium, and gas production 

 is shown by bubbles caught in the coagulum. (Hiss and Zinsser: Text-book of 

 Bacteriology,- 1910, p. 132.) 



2 Fitzgerald: Proc. Soc. Biol, and Med-, 1913, Vol. X, pp. 52-53. 



' Winslow, Kligler and Rothberg, Journal of Bacteriology, 1919, 4, 429-503. 



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