1907.] Bacteria of the Typhoid-coli Group, etc. 335 



were ultimately able to ferment saccharose. B. typhosus also acquired the 

 property of fermenting dulcite and lactose. 



The dysentery bacilli of Kruse and Flexner were ultimately able to 

 ferment saccharose within 24 hours. B. acidi laclici, after several generations, 

 fermented saccharose, and thus fell into the same sub-group as B. lactis 

 aerogenes. B. dysenterim Kruse was also induced to ferment lactose, and so, 

 fermenting glucose, saccharose, and lactose, came to be placed in the same 

 sub-group with B. lactis aerogenes, and in this respect may be regarded as 

 having fallen from the top of the typhoid-coli group to the bottom. Similar 

 changes in the case of other micro-organisms ultimately led to the belief that 

 division into distinct sub-groups separated by fermentation tests is impossible. 

 The fermentation reactions are characterised by acid reactions, but are rarely 

 accompanied by the production of gas. Special experiments were carried 

 out with a typhoid bacillus which had acquired the power to ferment dulcite. 

 When -such a culture was plated out on agar, sub-cultures from single colonies 

 retained the dulcite disruptive powers, although they were still capable of 

 being agglutinated by a typhoid immune serum, thus proving that the 

 fermentation was not due to any contaminating microbe. On inoculating 

 the dulcite fermenting typhoid culture into a guinea-pig, sub-cultures were 

 obtained showing the same reactions and these reactions were also maintained, 

 even when the microbe was grown for several generations on ordinary peptone 

 agar. 



Conclusions. 



1. A large number of glucosides may be fermented by many members of 

 the typhoid-coli group of bacteria. The fermentations vary with the micro- 

 organism tested, and the variations are as marked inside each sub-group 

 of bacteria as between adjacent sub-groups. 



2. The sugar-fermenting powers of an organism may be artificially changed 

 by growing the said organism for a succession of generations in media 

 containing a sugar which at the commencement of the experiment it was 

 unable to ferment. 



By this means a pathogenic organism may be altered until it gives 

 fermentative reactions characteristic of a non-pathogenic member of its 

 group. It is possible, indeed, that pathogenic organisms in the typhoid-coli 

 group may so alter their characters that they become unrecognisable when 

 growing for some time outside the body in soil, water, etc. 



If this is so, it might partly account for the difficulty experienced in 

 isolating B. typhosus from these situations. 



It also seems possible that a non-pathogenic organism may lose its 



