316 
Transactions of the Boyal Society of South Africa. 
original type has been classified as B. coli, the question as to which varieties 
represented " typical " B. coli as apart from atypical " forms has been 
studied in connection with the bacteriology of water (Houston and others). 
Much confusion has resulted, however, as regards the definition of a typical 
B. coli owing to the different identification standards set up by various 
observers. Some of these definitions have been too limited in their applica- 
tion and different degrees of importance have been attached to different 
characters (Savage, Prescott and Winslow, Konrich, Reports of the 
English and American Committees on standard methods for the examination 
of water). 
While there has been considerable variation in the criteria adopted by 
different workers for the identification of the colon bacillus, the characters 
generally accepted as common to the whole group of B. coli''' may be 
summed up as follows : G-ram-negative, aerobic, facultatively anaerobic 
non-sporing bacilli growing at 37° C, and fermenting glucose and lactose. 
Other characters, e.g. different fermentative reactions, motility, indol 
production, Voges and Proskauer reaction, simply determine the differentia- 
tion of separate types. Thus the term " lactose-f ermenter " has been 
frequently used as a convenient designation for the group (MacConkey). 
The question arises as to whether gelatin-liquefying, G-ram-negative 
bacilli which correspond in other characters to B. coli types are to be 
included in this biological group. Among the lactose-fermenters classified 
by MacConkey certain gelatin liquefiers were represented, e.g. B. cloacae, B. 
oxytocus perniciosus, and other authorities (Prescott and Winslow) have 
accepted this reaction as one of the possible characters of the group. In my 
own experience of a large number of coliform strains from faeces, urine, etc., 
and also water (Egypt, 1915-1918) I have never met with gelatin-liquefying, 
C-ram- negative, aerobic, non-sporing bacilli capable of growing at 37° C. 
apart from those referable to the B. jproteus type.* 
While the characteristic B. coli has the property of fermenting lactose, it 
is doubtful (as will be shown later, p. 350) if lactose fermentation can be 
regarded as a specific character of a particular group of intestinal bacilli, and 
studies on the variation of these organisms {v. p. 360) have shown how 
certain types only acquire this property by mutation on culture medium. 
Thus non-gelatin-liquefying, glucose-fermenting, non-lactose-fermenting 
bacilli of intestinal origin have to be considered in any system of classifica- 
tion of the G-ram-negative intestinal bacilli. 
Prom our present knowledge of the aerobic intestinal bacilli it would 
appear more rational from the purely biological standpoint to recognise a 
* B. proteus : Gram-negative, motile, aerobic, non-sporing bacilli, growing well at 
37° C, showing- a tendency to "spreading" type of growth, fermenting glucose with 
or without gas, not fermenting lactose, dulcite or mannite, varying in fermentation 
of saccharose and in indol formation, liquefying rapidly gelatin or solidified serum. 
