308 APPLIED BACTEBIOLOGY 



in many cases, whilst the colon bacillus developed, the 

 growth of the B. typhosus was restrained. 



Holz has used faintly acid potato-juice, thickened with 

 10 per cent, of gelatine, with or without the addition of 

 0'05 per cent, of phenol, with satisfactory results. This 

 method is practically the same as Eisner's, except that the 

 potassium iodide is replaced by phenol. Gasser, Holz, 

 Lyonnet, and others have suggested the use of various 

 media tinted with fuchsine and other aniline dyes. The 

 typhoid and colon bacilli are stated to decolourise, or to 

 cause other changes, in such media where the growth of 

 the colonies occur, whereas other organisms do not possess 

 this property. Little reliance can, however, be placed on 

 these appearances, as we have found other organisms give 

 the same characteristics as the typhoid and colon bacilli. 



After a considerable experience in the use of the above 

 methods, we find that the best and most reliable processes 

 to be employed for the isolation of the typhoid bacillus 

 from water are the use of carbol-gelatine (0"05 per cent.), 

 Eisner's method, and Parietti's acid carbolised broth. As 

 soon as the colonies which develop on the carbolised or 

 potato-gelatine become sufficiently advanced they are 

 examined with a lens, and any suspicious colonies are care- 

 fully subcultured into faintly alkaline sterile milk-tubes, 

 which are then incubated at 37° C. for thirty- six hours. 

 The milk-tubes are then examined, and any that have 

 become coagulated are rejected, as certainly not typhoid. 



From the tubes that have not coagulated the following 

 subcultures are prepared : (a) Gelatine ' streak ' culture ; 

 (b) gelatine ' shake ' culture ; (c) broth culture. 



The gelatine cultures are kept for three days at a 

 temperature of from 18° to 20° C. The broth-tubes are 

 incubated at blood-heat for the same length of. time, and 

 .then tested by the indol reaction. 



