CH. v] VARIATIONS IN FERMENTING POWER 53 



colonies some of which were coloured and others white. In 

 one experiment the coloured strain formed acid in salicin 

 and coniferin, which neither the original strain nor the white 

 colonies was able to accomplish. 



Klotz (1906) has described a coliform organism which did 

 not ferment lactose or saccharose when first isolated from 

 water but fermented both after 48 hours' growth on the media. 



Horrocks (1911) describes a strain of B. typhosus whic^n 

 after 3 days' growth on bile-salt-glucose-litmus-agar gave 

 typical fermentation tests but a week later was found to have 

 acquired the power to ferment lactose, dulcite and salicin. 



Normally B. typhosus ferments glycerine. Penfold (1910 a) 

 found that an old laboratory culture of this organism on agar, 

 when plated out, gave some colonies which fermented glycerine 

 and others which failed to do so even after five successive 

 subcultures had been made into peptone water. 



Many observers have recorded instances of dysentery 

 bacilli acquiring during cultivation the power of fermenting 

 sugars which previously they were unable to attack — such as 

 (in the case of the "Shiga" organism) mannite (Torrey, 1905), 

 the di-saccharides (Kruse, quoted by Bahr). Bahr (1912) 

 records the loss, on the part of an atypical "Shiga" organism, 

 of power to ferment saccharose after 6 months subculture, 

 and maltose after 7 months subculture ; the loss on the part 

 of an atypical "Flexner" organism of power to ferment 

 lactose after 4 months, accompanied by a temporary loss of 

 the power to ferment maltose. He quotes records of a similar 

 loss of power to ferment lactose after 4 years (Morgan), and 

 maltose after 9 years (Lentz). Another strain of the "Flexner" 

 type (after a month's subculture) produced a feebly acid 

 reaction in mannite at the end of 24 hours but after 10 days 

 further incubation the medium became definitely alkaline. 

 After further cultivation for some weeks it produced acidity 

 in mannite in 24 hours. Its action on maltose varied greatly. 



Sorenson (1912, quoted by Dobell) has recorded the case 

 of a patient, suflfering from glycosuria who also developed 

 pneumaturia. The gas formation was found to be due to a 

 .peculiar bacillus, " B. pnetmiaturiae," which had gained 



