A Study of the B. coll Group. 
317 
large class of intestinal bacilli having the common characters : aerobic, Gram- 
negative, non-sporing, growing at 37° C, fermenting glucose with or without 
gas production, not liquefying gelatin ; comprising certain specific patho- 
genic organisms specially designated, and identified by cultural and 
serological characters, e. g. B. typJiosus, etc., and a large number of sapro- 
phytic, though potentially pathogenic, varieties which can be generally 
classified into different types according to their cultural characters. The 
term B. coli (if it is to be used at all) in its widest application would thus 
become referable to those members of the class which do not possess 
specific pathogenic properties irrespective of certain cultural characters, 
including lactose fermentation. The term " typical B. coli " would be used, 
if necessary, to designate those types (fermenting lactose, clotting milk, and 
producing indol) which are most prevalent in the intestine, and therefore 
undoubted indicators in water of recent sewage pollution. The only 
justification for recognising a special group of " lactose fermenters " depends 
on the statistical fact that these types are most prevalent in fresh animal 
excreta, but it is questionable if the statistical basis can be used for a 
biological classification. 
The further question arises as to the significance of gelatin liquefaction, 
and whether a wider definition of the class is required, i. e. to include B. 
proteus. It must be admitted that with the exception of gelatin liquefac- 
tion, types of B. proteus may correspond closely to certain non-liquefying 
intestinal bacilli. 
Organisms of the B. faeccdis alkali genes type have also to be considered 
in regard to the classification of the Gram-negative intestinal bacilli. B. 
faecalis alhaligenes has been long recognised as differing from the motile 
organisms of the coli-typhoid class in the " terminal " position of its flagella, 
as opposed to the *' lateral " arrangement in the case of B. coli and B. 
typhosus (Berghaus, Klimenko). While this is true for my own observa- 
tions of these organisms, non-motile, Gram-negative, aerobic bacilli which do 
not ferment glucose or any other sugar have been frequently noted in 
dysenteric stools, and strains of this type have been found which on first 
isolation did not ferment glucose, and only gained this property after a period 
of growth in a glucose medium. This might appear to link up organisms of 
the B. faecalis alkaligenes type with the sugar-fermenting intestinal bacilli. 
The " lactose-fermenters " have been the subject of much careful study : 
originally different classical types had been separately described, e.g. B. coli 
communis, B. neapolitamis (Emmerich), B. acidi lactici (Hiippe), B. lactis 
aerogenes (Escherich), etc., and these names may still be retained for 
organisms which accurately correspond to such classical strains. 
The work of MacConkey on the lactose-fermenting coliform bacilli 
represented the first attempt in the direction of a rational system of 
classification of these organisms. 
