102 Kansas Academy of Science. 



bacteria. This is especially so in badly polluted waters, in which 

 case the gas-forming bacteria may be much overgrown and crowded 

 out by non-gas-producers. Hence, analysts have sought diligently 

 for a medium which would restrain the non-gas-producing bacteria, 

 and at the same time not interfere with the normal action of the 

 gas producers. 



In the Supplement to the Journal of Infectious Diseases, May 

 3, 1907, Daniel D. Jackson presents an article on the ''Use of a 

 Lactose-bile Medium" which at that time had proved to be reliable 

 in presumptive tests for B coli. 



The lactose-bile medium is prepared by drawing liquid ox bile 

 directly from the animal and sterilizing it. The bile is then fil- 

 tered and to it is added one percent, of lactose previously dissolved 

 in a small amount of water, after which it is drawn oflp into fermen- 

 tation tubes and sterilized in an autoclave for thirty minutes at 

 fifteen pounds pressure. The ordinary plain fermentation tubes 

 may be used, but Jackson recommends tubes 140 mm. long and 15 

 mm. in diameter, having an elongated bulb 38 mm. in its shortest 

 diameter. This admits of the use of a considerable quantity of the 

 water to be tested without too great dilution of the medium. 



Mr. Jackson reports that at Mount Prospect laboratory, Brook- 

 lyn, N. Y., about 5000 samples of water of various degrees of purity 

 and from hundreds of different sources have been tested by this 

 medium and the results agreed with the judgments formed by the 

 complete analyses of the samples as well as by careful sanitary in- 

 spection of the sources of supply. In many instances contamina- 

 tion has been found to exist which would not otherwise have been 

 detected. 



The extreme efficiency of this ox-bile medium in tests for B. coli 

 is due to the selective inhibiting power of the cholic acid radical 

 of the bile by which bacteria other than the colon bacillus are 

 restrained or killed. Nearly all the bile salt present is in the form 

 of a glycocholate. Experiments show that no meat extract is 

 needed, as the bile contains albuminous matter enough to feed the 

 bacteria. 



It has been the practice at the Ottawa laboratory to procure from 

 the local butcher ox galls in sufficient number to yield a quart of 

 bile at a given time. The bile is drawn out, autoclaved and kept 

 in plugged flasks in a liquid form until needed. It may be 

 evaporated to dryness and kept in the form of powder. In this 

 case, however, it must be perfectly dry or in a short time it will 

 become too acid for use. A gram of lactose, 11 grams of solid bile 



