208 BACTERIOLOGICAL EXAMINATION OF WATER. 



have the appearance of moulds ; later they spread out, become 

 more blue in colour, and may attain the size of a 50-centime 

 piece. When the typhoid bacillus has great vitality, as for 

 example, if it comes from the spleen, its superficial colonies 

 more resemble those of B. coli. The deep colonies, however, 

 preserve their typhoid aspect. When the B. coli is feeble, its 

 deep colonies are less distinct ; they may lose their brownish 

 colour and become blue ; in this case they have a more 

 marked blue colour than the colonies of B. typhosus. When 

 plates are made in the medium from a fresh mixture of 

 B. coli and B. typhosus, there is a very marked difference 

 between the colonies of these organisms both in the depth 

 and on the surface; the development of gas bubbles, 

 however, is too irregular to be of much value. The great 

 points are the brownish colour and the opacity of the coli 

 colonies as compared with the transparent bluish colonies of 

 B. typhosus. At times the varieties of B. coli, especially when 

 they have been isolated from water, show colonies in the depth 

 which are quite indistinguishable from those of B. typhosus. 



Remy^s medium is not elective ; other bacteria grow on it, 

 but not so well as B. coli and B. typhosus. It is, however, 

 fairly easy to prepare, and, being of constant composition, 

 might replace the Eisner potato-gelatine medium with 

 advantage. 



Remy points out that it is better to directly plate out a 

 suspected water on his gelatine, containing 0*25 and 0*5 per 

 1000 of carbolic acid, than to pass the specimen through car- 

 bolic acid broth before making the plates. After ten days 

 association with B. coli, the B. typhosus is said to become 

 enfeebled, and if the weakened organism is passed through 

 carbolic broth, containing only 1 per 1000 of carbolic acid, it 

 is apt to die out. Remy has found that B. typhocus, after 

 being associated for thirty-eight days with B. coli, can be 

 easily isolated by directly plating out the water in his special 

 medium. But when the mixture of the two organisms is 

 passed through carbolic acid broth, the typhoid bacillus cannot 

 be found in the gelatine plates made from the carbolised broth 

 if more than ten days have elapsed since the admixture of the 

 typhoid with the colon bacilli. He also suggested that typhoid 



