BACTERIOLOGY OF WATER 235 



c.c. of the water are added to 50 c.c. of nutrient broth, 

 to which, after three or four days' incubation at 37 C., 

 an addition of the typhoid serum is made, and after 

 standing for some hours and centrifuging, the deposit is 

 plated out. 



(d) Hoffmann and Ficker's Enrichment Method. The 

 water itself is converted into a nutrient medium by the 

 addition of 1 per cent, of nutrose, O5 per cent, caffeine, 

 and O'OOl per cent, of krystal violet. The mixture is 

 incubated at 37 C. for twelve to thirteen hours, by which 

 time the typjioid bacilli should have multiplied to such 

 an extent as to permit of direct isolation by plating, the 

 B. coli being inhibited. It is very doubtful whether this 

 medium is really satisfactory. The action of caffeine on 

 B. coli is uncertain, while krystal violet merely inhibits 

 water organisms. 



(e) Process of Cambier. A special alkaline peptone 

 medium is placed in a glass jar. In this is immersed a 

 Pasteur-Chamberland filter candle half filled with the 

 same solution, to which is added a little of the fluid to be 

 examined, and the whole is incubated at 37 C. Sooner 

 or later growth appears in the fluid outside the candle, 

 and Cambier states that if typhoid bacilli be present 

 they will make their appearance before B. coli. Most 

 of those who have tried this process find that organisms 

 will grow through, but they are usually not B. typliosus. 



(/) Wilson adds 10 c.c. of nutrient broth to every litre 

 of the water, and evaporates at reduced pressure at 42 C. 



Isolation of the Typhoid Bacillus. The concentrated 

 deposit obtained is plated out on a medium chosen for the 

 more or less characteristic growth of typhoid bacilli 

 thereon, and for its ability to inhibit the growth of most 

 other organisms. Conradi-Drigalski agar, litmus lactose 

 bile-salt agar, Fawcus's medium, China green agar, or 

 one or other of a host of media all devised for this purpose, 

 may be employed. Of one thing a bacteriologist may 

 be certain: he will always get colonies portraying the 

 characters of a typhoid colony on that medium. These 

 colonies must all be subcultured into broth and their 

 attributes worked up (see pp. 97 and 108). If plenty of 

 typhoid serum is available; it is advisable to try agglutin- 

 ating reactions on each subculture as soon as possible. 

 Pfeiffer's test should be done to clinch a diagnosis. It 



