114 BACTERIOLOGY OF WATER, AIR, MILK, ETC 



NOTE. The reduction of neutral red with a greenish-yellow 

 fluorescence is very striking and has been suggested as a test for the 

 colon bacillus. Many other organisms, especially those of the hog 

 cholera group, have this power. It is convenient, however, to color 

 glucose bouillon with about i% of a 1/2% solution of neutral red. 



Isolation of the Typhoid Bacillus from Water. 



This is probably the most discouraging procedure which can be 

 taken up in a laboratory. Only the most recent reports of such isola- 

 tion from water supplies, which have been verified by immunity reac- 

 tions, can be accepted and of these the number of instances is exceed- 

 ingly small. Owing to the long period of incubation, the typhoid 

 organisms may have died out before the outbreak of an epidemic 

 suggests the examination of the water supply. 



There have been various methods proposed for the detection of 

 the B. typhosus in water. A method which w r ould offer about as 

 reasonable a chance of success as any other would be to pass 2 or 3 

 liters of the water through a Berkefeld filter; then to take up in a 

 small quantity of water all the bacteria held back by the filter. Then 

 plate oat on lactose litmus agar and examine colonies which do not 

 show any pink coloration. The dysentery bacillus has about the same 

 cultural characteristics as the typhoid one, so that it is important to 

 note motility. If from such a colony you obtain an organism giving 

 the cultural characteristics of B. typhosus, carry out agglutination and 

 preferably bacteriolytic tests as well. Some strains of typhoid, espe- 

 cially when recently isolated from the body, do not show agglutination. 



The Conradi Drigalski, the malachite-green and various caffeine 

 containing plating media have been highly recommended. 



Isolation of the Cholera Spirillum from Water. 



The method proposed by Koch in 1893 does not seem to have been 

 improved upon by later investigators. To 100 c.c. of the suspected 

 water add i% of peptone and i% of salt. Incubate at 38 C., and at 

 intervals of 8, 12 and 18 hours examine microscopically loopfuls taken 

 from the surface of the liquid in the flask. So soon as comma-shape 



