422 A MANUAL OF BACTERIOLOGY 



By tlit' use of malachite or brilliant green media, the last- 

 named difficulty seems to have been overcome (see section 

 on "Water"). 



In sterilised waters, including distilled water, the Bacil- 

 lus typJiosus maintains its vitality for upwards of a month, 

 and in some cases for much longer. The survival is not 

 necessary longer in an organically polluted water than 

 in a pure water. Infecting sterilised Thames water (from 

 the Temple Embankment) and sterilised tap-water of the 

 Chelsea Water-works with typhoid cultures, the author 

 found that, examining small quantities (1 c.c.) of the 

 water, the bacillus appeared to die out in the former in 

 two to three weeks, in the latter in four to five weeks. 



The survival of the typhoid bacillus in natural waters 

 must be influenced by many circumstances temperature, 

 chemical composition, struggle for existence with the 

 natural bacterial flora, etc., of the water. Experiments 

 by Russell and Fuller, 1 in which the organism, suspended 

 in collodion sacs, was subjected to the action of lake water, 

 indicated that the maximum was eight to ten days. 

 Houston, 2 using raw Thames, Lee, and New River waters 

 artificially infected with varying quantities of ordinary 

 laboratory typhoid cultures, and examining quantities of 

 100 c.c. of the water, found that in none of eighteen 

 experiments was a negative result obtained in four weeks, 

 and it was only after nine weeks that the typhoid bacillus 

 could not be isolated from this quantity in all the experi- 

 ments. But in subsequent experiments, 3 in which typhoid 

 bacilli, obtained directly from the urine of a carrier case 

 by centrifuging and without culturing, were added to 

 the water, the number of bacilli was reduced by 99-99 per 

 cent, after a week, and 'after ten days the organism 



1 Journ. Infect. Diseases, Sup. No. 2, February, 1902, p. 40. 



2 First Hep. on Research Work, Metropolitan Water Board, 1908. 



3 Sixth Research Report, Metropolitan Water Board, 1911. 



