The Fermentation Tnbe 219 



colon group which may be divided into a saprophytic and a 

 parasitic sub-group as follows : 



A. Saprophytic sub-group. 



ra. Ferment all three sugars with same rapidity. . . 



Bacillus of grouse disease and some colon bacilli, 

 lb. Ferment glucose and lactose rapidly, saccharose 



slowly. . . . B. colt a (la and ib). 

 2. Ferment glucose and lactose rapidly, saccharose not 



at all. . . . B. coli /3. 



B. Parasitic sub-group. 



I. Ferment glucose rapidly, saccharose and lactose not 

 at all. ... all pathogenic forms. 



I am inclined to associate this loss of functional activity in 

 the pathogenic group B with an adaptation to a more para- 

 sitic existence and the development of certain other powers — 

 the formation of toxic substances perhaps — which enables them 

 to live in competition with living tissues while they have 

 largely forfeited their power to compete with the more sapro- 

 phytic forms from which they may have originally sprung. 



It might be claimed that the phylogenetic loss of gas pro- 

 duction is simply a change in the kind of fermentation, from 

 the butyric to the lactic for example. That this is not true 

 can be readily demonstrated, for in saccharose and lactose 

 bouillon, when muscle glucose is absent and no gas appears 

 in consequence, the reaction of the bouillon does not become 

 acid. Among those bacteria which act upon sugars without 

 the development of gas, a strongly acid reaction appears with- 

 in twenty-four hours. The failure of the group B to act upon 

 lactose is furthermore shown by their inability to produce 

 coagulation of milk. We have, therefore, no ground for as- 

 suming a change in the type of fermentation. It is an abso- 

 lute loss of function and not a modification. 



In bringing together the more detailed observations on gas 

 production a certain number of interesting facts claim our at- 

 tention. We note that in the B. coli type of gas production in 

 glucose only a certain quantity of gas collects — 45 to 60 per 

 cent, of the capacity of the closed branch — while in the B. 



