408 Profs. Percy Frankland and Marshall Ward. 



Phenol 5 grams. 



Hydrochloric acid (pure) 4 



Distilled water 100 



(In practice, I generally employ some tubes to which 3 drops 

 (= 0'25 c.c.) and others to which 5 drops (= 0'4 c.c.) of this solu- 

 tion have been added.) 



To the tubes thus treated, from 1 drop to several cubic centimetres 

 of the water under investigation are added, and, after thoroughly 

 mixing the contents, the tubes are placed in the incubator at 37 C. 

 As soon as the tubes become turbid (which in the initial presence of 

 many typhoid bacilli will occur already in twenty-four hours, but if 

 only few are present, may be postponed for forty-eight, seventy-two, 

 or even more hours) they are submitted to ordinary plate cultivation 

 in three dilutions, the second and third dilutions only being actually 

 poured on to plates or into Petri dishes, whilst the first dilution 

 gelatine-tube should be preserved to see if gas-bubbles develope in it. 



The gelatine-plates thus prepared are frequently found to yield 

 nothing but typhoid colonies, whilst in some cases the latter are 

 mixed with the colonies of water-bacteria, and in some cases, again, 

 there are only colonies of water-bacteria on the plates, In no case 

 must it be concluded, from the mere appearance of the colonies that 

 typhoid is present, but the colonies must always be submitted to the 

 further tests of 



1. Microscopic examination. 



2. Inoculation on to potatoes, and comparison of growth with that 



of simultaneous cultures of the typhoid bacillus on the same 

 potatoes. 



3. Inoculation into broth, and examination of the broth-culture 



after forty-eight hours' growth in the incubator at 37 C. for 

 indol, which, if it is the typhoid bacillus, should be absent. 



4. Inoculation into milk, which should not subsequently become 



coagulated on keeping for one week in the incubator. 



5. Inoculation into a tube containing melted gelatine-peptone ; on 



distributing the bacilli in this and then congealing the gelatine, 

 no gas-bubbles should be formed on keeping at 18 20 C., 

 whilst in the case of the B. coli communis bubbles will make 

 their appearance in from twelve to forty-eight hours. 



The B. coli communis, as already pointed out, is even less sensitive 

 to phenol and acids than the typhoid bacillus. In the case of those 

 unsterile waters infected with the B. coli communis, the above method 

 was similarly employed for its detection. 



The above outline will show that a systematic investigation of the 

 behaviour of the typhoid bacillus in un sterilised waters is attended 

 with considerable difficulties, and involves an enormous amount of 



