548 Profs. Percy Frankland and Marshall Ward. 



bacilli when the introduced water bacteria had undergone extensive 

 multiplication. 



8. The addition of common salt to unsterile Thames water, in the 

 proportion of O'l, 1, and 3 per cent., causes the. enormous multiplica- 

 tion of the water bacteria present, the most striking result in this 

 respect being obtained with the largest addition of salt. 



9. The addition of common salt to typhoid- infected unsterile 

 Thames water diminishes the duration of life of the typhoid bacilli in 



this water, thus : 



Duration of life of 

 typhoid bacillus. 

 Unsterile Thames water kept at 6-8P C.. . } Between 25 and 34 days. 



Ditto with O'l per cent, salt" kept at 68 C ....... 25 33 



19 C ....... Less than 18 days. 



Ditto with 1 per cent, salt, kept at 6 8 C ......... 



_ 



Ditto with 3 per cent, salt, kept at 6 8 C 



18C 



10. This more rapid disappearance of the typhoid bacilli in the 

 unsterile Thames water to which salt was added cannot be wholly, 

 but only in part, attributed to the resulting multiplication of the 

 water bacteria, as the addition of salt in similar proportion to typhoid- 

 infected steam-sterilised Thames water also caused an exceedingly 

 rapid disappearance of the typhoid bacilli, although the disappearance 

 was not so rapid as in the same water to which a few drops of un- 

 sterile Thames water had been added, and in which, therefore, a 

 great multiplication of the water bacteria took place, thus : 



Duration of life of 



typhoid bacilli. 

 Steam-sterilised Thames water with 1 per cent, salt, Between 12 and 19 days. 



kept at 912 C. 



Ditto, to which also a few drops of unsterile Thames Less than 5 days. 

 water were added, and in which extensive multi- 

 plication of the so-introduced water bacteria took 

 place 



11. The Bacillus coli communis, taken from ordinary agar-agar 

 cultures and introduced into steam-sterilised Thames water, under- 

 goes considerable multiplication, when under precisely similar con- 

 ditions the typhoid bacillus does not multiply. 



The behaviour of the B. coli communis in the steam-sterilised waters 

 may be summarised as follows : 



