BACILLUS-COLI-LlKE BACTERIA FROM FECES AND SEWAGE 29 



formers if gas is observed in the closed arm irrespective of the 

 quantity. 



Table 12 indicates that with sucrose, raffinose, and dulcitol, acid- 

 and gas-production after 36 hours' incubation at 37 C. are strikingly 

 correlated. Of 80 organisms which fail to form gas from sucrose, 79 

 (98.8%) form less than 0.2% normal acid, and the remaining culture 

 forms only 0.2% normal acid. Among the 75 organisms which do 

 give gas from sucrose, 8 (10.6%) form more than 0.4 but less than 

 0.6%, 48 (64%) give between 0.6 and 0.79%, and the remaining 19 

 strains (25.4%) form more than 0.8% normal acid. There is no over- 

 lapping whatever between the amounts of acid produced by the gas- 

 formers and the nongas-formers. To summarize: of the 80 strains 

 which fail to produce gas, none form more than 0.2% normal acid, 

 while among the 74 gas-producers the minimal amount of acid pro- 

 duced in peptone solution containing 1% sucrose is more than 0.4% 

 normal acid. 



A similar correlation is observed between acid- and gas-formation 

 in 1% dulcitol in peptone solution. Of 88 strains that do not form 

 gas, 86 (97.8%) give less than 0.2% normal acid. The remaining two 

 organisms form 0.3% and 0.4% normal acid. Among the 67 gas- 

 formers, however, there are only 2 (3%) that produce less than 0.4% 

 normal acid. 



The correlation of acid- and gas-production in peptone raffinose 

 solution is also very marked ; 79 produce gas and 77 fail to form gas 

 from raffinose. Of the nongas-formers 72 (93.5%) form less than 

 0.2% normal acid; 3 organisms (3.9%) between 0.2% and 0.6% acid; 

 and 2 cultures (2.6%) more than 0.8% acid. Among the gas formers 

 1 culture (1.3%) produces no acid, while 2 others (2.5%) form less 

 than 0.6% normal acid. The other 76 gas-formers (96.2%) form 

 more than 0.6% normal acid. 



With glycerol and salicin the correlation of acid-production and 

 gas-formation is not nearly so striking as it is with sucrose, dulcitol, 

 or raffinose. 



Gas is formed from glycerol by 118 of the cultures after 72 hours' 

 incubation, while 38 organisms do not form gas. Of the gas-formers, 

 16 (13.6%) produce 0.4-0.59% normal acid as compared with 23 

 (60.6%) of the nongas-formers, while 61 (51.7%) of the former and 

 5 (13.2%) of the latter give 0.6-0.79% normal acid. One organism 

 which does not form gas yields more than 0.8% normal acid. 



