BILE COMPARED WITH LACTOSE BOUILLON 77 



In some instances only a small bubble of gas appeared in the 

 inner tube in the bile fermentation tubes, while the production 

 of gas in lactose filled two-thirds of the inner tube. In one 

 instance a culture of B. paratyphosus B., which showed char- 

 acteristic agglutination in 1 : 500, was obtained from a lactose 

 fermentation tube. 



In order to obtain a direct comparison by total counts of the 

 growth of the B. coli group on lactose and on bile collected at 

 different times and stored for varying intervals, firm substrata 

 were prepared by adding 1.5 per cent agar to each medium. It 

 was found necessary to exert great care in filtering the bile agar 

 in order that the final product should be free from a precipitate 

 which would render the counting of the colonies diflficult. The 

 bile was collected each week, sterilized, and either made into 

 agar at once or stored at 1°C. until used. For the tests, fifteen 

 strains of B. coli, with characteristics described in the accom- 

 panying table, were grown for three days at 37°C., with daily 

 transfers in 10 cc. nutrient broth. 



In recording the results, it was found that the inhibition by 

 the bile could be shown more clearly by taking the number of 

 colonies which developed upon the bile agar as one, and con- 

 sidering the multiple of this number, which expressed the count 

 on lactose agar from the same dilutious of the original culture 

 plated and incubated at the same time, as the ''ratio of inhibition" 

 of the bile. 



The bile which was collected during the month of June (see 

 table) was tested with the cultures two days after receipt and 

 again some weeks later. With a few exceptions the inhibition 

 exerted by the fresh bile was less, in amount, and more regular 

 for the different strains than that of the same bile after storage. 

 When the actions of the various organisms upon the individual 

 samples of bile are considered, it is seen that the variations in 

 the degree of inhibition are greater for the bile that was held in 

 storage before being tested; and, in general, this variation in- 

 creased with the time of storage. One sample of bile (see table, 

 (e) ) was of a pronounced red color and contained a heavy red- 

 brown precipitate. This sample showed an inhibitive action, 



