QUALITATIVE BACTERIOLOGICAL ANALYSIS. 189 



B. COLT COMMUNIS. 



(3) Gelatine-slope. Thick, broad 

 greyish-white growth with a cremated 

 margin. 



(4) Witters Peptone and Salt Solu- 

 tion. Indol produced, 



(5) Mint. Coagulated. 



(6) Litmus-whey, one week at 37 

 C. Acid produced, usually requiring 



B. TYPHOSUS. 



(3) Thin narrow greyish- white 

 growth, crenated margin not marked 

 as in B coli. 



(4) No formation of indol. 



(5) Unchanged after a month. 



(6) Very small amount of acid 

 produced, requiring not more than <5 



N 



from 20 to 40 per cent, of , ~ alkali to per cent, of ; alkali to neutralise it. 



neutralise it. 



(7) Neutral -red Glucose -agar. 

 Marked green fluorescence. 



(8) Glucose - gelatine and Lactose- 

 gelatine Shake Cultures, and Glucose- 

 agar-stab. Marked gas formation. 



(9) Gelatine, 25 per cent, incubated 

 at 37 C. Thick film appears on the 

 surface. 



(10) Potato. As a rule, a thick 

 yellowish-brown growth. 



(11) Proskauer and Capald'C s Media , 

 No. I., after twenty hours. Growth, 

 medium acid. 



No. II. , after twenty hours. Growth , 

 medium neutral or faintly alkaline. 



(12) titrate - broth. Nitrate re- 

 duced to nitrite. 



(13) Microscopical Appearances. 

 A small bacillus often like a coccus, 

 not motile as a rule. 



(14) Flagella. Usually 1 to 3, short 

 and brittle ; sometimes 8 to 12, long 

 and wavy. 



(15) Agglutination. As a rule, no 

 agglutination with a dilute anti-ty- 

 phoid serum. 



(7) No change. 



(8) No gas formation. 



(9) No film appears on the surface, 

 but a general growth takes place 

 throughout the tube. 



(10) Thin transparent growth hardly 

 visible to the naked eye. 



(11) No. I., no growth or change in 

 the reaction of the medium. 



No. II.. Growth, medium acid. 



(12) Keduction of nitrate not so 

 marked. 



(13) Usually longer than B. coli : 

 highly motile, with a quick serpentine 

 movement. 



(14) Usually eight to twelve, long 

 and wavy. 



(15) Marked agglutination with di- 

 lute anti-typhoid serum. 



The " atypical " members of the Coli group which fail to coagu- 

 late milk and do not produce indol sometimes give rise to difficul- 

 ties in diagnosis, but most of them, as a rule, can be distinguished 

 by the production of gas in glucose media. In polluted waters, 

 however, coliform organisms occur which are not so readily dis- 

 tinguished. The four varieties of B. typhosus simtilans, de- 

 scribed by Houston, are instances of this class of micro-organisms. 

 When investigated they showed the following characteristics : 



