BACTERIA IN WATER 6^ 



in a fresh and young stage, it is difficult to differentiate 

 Koch's comma from many other curved bacilli. 



Its cultivation characters are not always distinctive. 

 Microscopically the young colonies in gelatine appear as 

 cream-coloured, irregularly round, and granular. Lique- 

 faction sets in on the second day, producing a somewhat 

 marked ** pitting " of the medium, which soon becomes 

 reduced to fluid. In the depth of gelatine the growth is 

 very characteristic. An abundant, white, thick growth 

 exactly follows the track of the needle, here and there often 

 showing a break in continuity. Liquefaction sets in on the 

 second day, and produces a distinctive ** bubble '* at the 

 surface. The liquefied gelatine does not fall from the sides 

 of the tube, as in the Finkler-Prior comma of cholera nostras, 

 but occurs inside the border where the gelatine joins the 

 glass. In the course of a week or two all the gelatine may 

 be reduced to fluid. On agar Koch's comma produces with 

 rapidity a thick, greyish, irregular growth. On potato, 

 especially if slightly alkaline, an abundant brownish layer is 

 formed. Broth and peptone water are excellent media. 

 In milk it rapidly multiplies, curdling the medium, with 

 production of acid. Unlike Bacillus coli, it does not form 

 gas, but, like B. coli, it produces large quantities of indol 

 and a reduction of nitrates to nitrites. Hence the indol test 

 may be applied by simply adding to the peptone culture 

 several drops of strong sulphuric acid, when in the course 

 of several hours, if not at once, there will be produced a 

 pink colour, the *' cholera red reaction." Although it 

 readily loses virulence, and its resistance is little, the comma 

 bacillus retains its vitality for considerable periods in moist 

 cultures, upon moist linen, or in moist soil. In cholera 

 stools kept at ordinary room temperature the cholera bacil- 

 lus will soon be outgrown by the putrefactive bacteria. The 

 same is true of sewage water. 



The lower animals do not suffer from any disease at all 



