156 BACTERIA 



flagellum of thirty micromillimetres ; but its movement was 

 slow. 



As we have already seen, the most astonishing property 

 of this organism is its ability to grow and perform its specific 

 function in solutions absolutely devoid of organic matter. 

 Some authorities hold that it acquires its necessary carbon 

 from carbonic acid. The mode of culturing it is as fol- 

 lows: 



To sterilised flasks add 100 cc. of a solution made of one 

 gram of ammonium sulphate, one gram of potassium sul- 

 phate, and 1000 cc. of pure water. To this add one gram 

 of basic magnesium carbonate which has been previously 

 sterilised by boiling. Now inoculate the flask with a small 

 portion of the soil under investigation, and after four or five 

 days sub-culture on the same medium in fresh flasks, and 

 let this be repeated half a dozen times. Now, as this in- 

 organic medium is unfavourable to ordinary bacteria of soil, 

 it is clear that after several sub-cultures the nitrous organism 

 will be isolated in pure culture. 



Winogradsky employs for culturing upon solid media a 

 mineral gelatine. A solution of from 3 to 4 per cent, of 

 silicic acid in distilled water is placed in flasks. By the 

 addition of the following salts to such a solution gelatinisa- 

 tion occurs: 



( Ammonium sulphate 0.4 gram 



(a) < Magnesium sulphate 0.05 



( Calcium chloride A trace 



( Potassium phosphate o.i gram 



(b) < Sodium carbonate 0.6, 0.9 



( Distilled water 100 cc. 



The sulphates and chloride are mixed in 50 cc. of distilled 

 water, and the latter substance in the remaining 50 cc. in 

 separate flasks. After sterilisation and cooling these are all 

 mixed and added in small quantities to the silicic acid. 



