Report on the Bacteriology of Water. 539 



Some previous observers, on the other hand, record the multiplica- 

 tion of the typhoid bacillus in potable waters with which they have 

 made similar experiments ; whilst others, again, have found no 

 multiplication. It appears to me highly probable that in most, if 

 not in all, cases in which multiplication has been observed, it has 

 been occasioned through the introduction of an appreciable amount 

 of food-material along with the typhoid bacilli; for, as already 

 pointed out, most investigators have exercised very little care in 

 respect of this highly important factor. 



But although the typhoid bacilli taken directly from an ordinary 

 cultivation and plunged into potable water may not be able to pro- 

 liferate in the latter, it appeared to me quite possible that if the 

 environment of the typhoid bacilli were gradually, instead of sud- 

 denly, changed, the requirements of the bacilli might perhaps be 

 thereby so far modified as to undergo multiplication in the aqueous 

 medium. For by gradually changing the surroundings, it would be 

 anticipated that those individuals most capable of nourishing under 

 the altered conditions would be propagated, and that each successive 

 generation of typhoid bacilli would thus become more adapted to the 

 new medium. 



To ascertain whether this process of education could be actually 

 accomplished, the following experiments were made. 



Education of Typhoid Bacilli for Aquatic Life. 



A gelatine-culture of the typhoid bacillus was, in the first instance, 

 inoculated into sterile broth of the ordinary strength, and kept at 

 Ifi 20 C. ; turbidity ensued in twenty -four hours. From this broth 

 cultivation an inoculation was made into 50 per cent, broth (broth 

 mixed with its own volume of water); this also became turbid in 

 twenty-four hours at 18 20 C. From the 50 per cent, broth culti- 

 vation an inoculation was made into 10 per cent, broth (1 volume of 

 broth mixed with 9 volumes of water) ; this liquid only became visibly 

 turbid in from two and a half to three days. After four successive 

 generations of cultivation in this 10 per cent, broth medium had been 

 carried on, the time elapsing between the inoculation and the appear- 

 ance of turbidity gradually diminished until, with the fifth generation, 

 turbidity already set in in twenty-four hours. From this 10 per 

 cent, broth, inoculation was then made into 1 per cent, broth 

 (1 volume of broth mixed with 99 volumes of water) ; this became 

 turbid in twenty-four hours. Continuous cultivation in this 1 per 

 cent, broth medium was then carried on for a period of two months, 

 after which it was employed for infecting steam-sterilised Thames 

 water, thus : 



On 31.1.1894, 2 drops of a 1 per cent, broth cultivation (three 

 VOL. LVI. 2 o 



