QUANTITATIVE BACTERIOLOGICAL ANALYSIS. 21 



THE DURATION OF LIFE OF MICRO-ORGANISMS. 



The life of micro-organisms may extend over a long period ; 

 this is especially the case when they possess the power of form- 

 ing spores. Duclaux found living spores of Tyrothrix after 

 five years existence in a fluid medium. He also showed that 15 

 out of 65 vessels which Pasteur used in his experiments on 

 spontaneous generation were capable of giving rise to new 

 cultures after being closed for from twenty to twenty-five years. 

 The reaction of the fluid in the fertile flasks was slightly alka- 

 line whilst the reaction in the sterile flasks was either strongly 

 acid or strongly alkaline. Miquel found after nine years only 

 220 living organisms in a flask which had originally contained 

 4,800 organisms. Another flask containing Vanne water which 

 originally showed 66 microbes per c.c. was found quite sterile 

 after being closed for ten years. 



Roth placed water, from a well, containing 5000 bacteria per 

 c.c. in sterile flasks and found 



After 2 days closure 80,000 organisms per c.c. 

 3 120,000 " 



5 60,000 

 10 43,000 

 4 weeks 2,200 



The presence of carbonic acid gas in a water has a great 

 influence on the duration of life of micro-organisms. Liborius 

 in his researches on anaerobes, showed that the development of 

 colonies was arrested if the air present in the nutritive gelatine 

 was driven out by carbonic acid gas. Leone found in a water 

 containing carbonic acid gas that out of 786 bacteria originally 

 present, only 87 could be detected after five days. 



Hochstetter^s researches showed that carbonic acid gas acted 

 differently according to the species exposed to its influence ; 

 some organisms were killed, others merely restrained in their 

 growth. In Seltzer water anthrax bacilli only lived for one hour, 

 but anthrax spores lived for several days. In water containing 

 carbonic acid gas the B. typhosus lived for five days, but the 

 Spirillum cholerae could not be detected after twenty-four 

 hours. The effect was not due to chemical changes nor to 

 pressure, but simply to the presence of carbonic acid gas. 



