ADDENDUM 185 



hypochlorite of lime has been extensively tested and found to be 

 very satisfactory in action. Alexander at Poplar has also re- 

 ported upon the satisfactory use of an electrolytic disinfecting 

 fluid which liberates chlorine. 



All these disinfection procedures should be carefully tested 

 and controlled by bacteriological methods. 



4. The isolation of B. typhosus from Water, Sewage, etc, 



The different methods and procedures are described at con- 

 siderable length on pages 39 44. While infrequently required 

 it is important that the most reliable methods should be used. 

 The following additional particulars will be of interest. 



Houston 1 has recently further studied this question and 

 compared several methods. He tested sewage artificially 

 inoculated with a small previously ascertained number of 

 typhoid bacilli, examining the first series of these experiments 

 in duplicate, using both direct platings on malachite green agar 

 plates and the enrichment method with ox-gall medium, and 

 the second series also in duplicate, using the same direct method, 

 but instead of ox-gall employing the brilliant green enrichment 

 method described by Browning, Gilmour and Mackie 2 . 



In all six experiments the typhoid bacilli were recovered in 

 considerable numbers (varying from 9 to 1 1 8), but in every case 

 by the direct method. In no case was a typhoid bacillus 

 recovered by either of the indirect methods. As carried out the 

 experiments were strictly comparable, and the tests were applied 

 to a sewage medium and not to typhoid excreta. This is 

 important since it allows direct deductions to be made from 

 them as to the reliability of the methods tested for the isolation 

 of typhoid bacilli from sewage or water. 



These experiments bear out the conclusion given on page 40 

 that "enrichment and selective enrichment methods are less 

 satisfactory than sedimentation or direct concentration." 



Stated briefly Houston's method for the examination of 

 water or sewage for the typhoid bacillus is as follows : 



500 c.c. of the sample is centrifugalised and the deposit 



1 Metropolitan Water Board : Tenth Research Report, 1914. 

 ^ Jo urn. of Path, and Bacteriology, 1913, xvm, p. 146. 



