EXPERIMENTS ON 
THE DIFFERENTIATION AND ISOLATION FROM 
MIXTURES OF THE BACILLUS COLI COMMUNIS 
AND BACILLUS TYPHOSUS BY THE USE OF 
SUGARS AND THE SALTS OF BILE 
By ALFRED MacCONKEY 
Physiologists tell us that in the bile of animals the salts occur in proportions 
different to those in the human subject, and bacteriologists find that animals are not 
susceptible to enteric fever. It has also been noticed that intestinal fermentation is 
greatly lessened by the administration of ' sodium taurocholate ' in keratin coated 
pills. 
These considerations suggested a research into the possibility of using the salts 
of bile as a means of — 
1. Differentiating the *B. c. c. from the B. t. a. 
2. Isolating the B. t. a. from mixtures of organisms. 
3. Finding an index of pollution of drinking waters. 
For many months experiments were made to ascertain whether ' sodium 
taurocholate ' had a different effect to ' sodium glycocholate.' The results were always 
the same, and it was concluded that these two salts behaved alike, until, quite 
accidentally, it was discovered that the chemist from whom the salts were obtained 
considered that the names were synonymous and had supplied mixed salts. 
Consequently these experiments must be considered as having been made with a 
mixture of the salts. The pure salts might give different results. 
Elsner's medium suggested the use of potato juice as a basis in the first series 
of experiments, but as potato juice has not always the same composition, later an 
attempt was made to secure uniformity by using pure salts. 
The effect of bile salts upon B. c. c. and B. t. a. may be considered under three 
headings : — 
I. Motility. 
II. Morphology. 
III. Duration of life. 
The medium consisted of slightly alkaline potato juice, with varying 
percentages of bile salts, and the incubation temperature was 37 0 C. 
B. c. c. = Bacillus coli communis. B. t. a. = Bacillus typhi abdominalis. 
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