ISOLATING THE TYPHOID BACILLUS. 435 



nature of a dew drop. Only in isolated instances is the 

 colony larger and more cloudy in appearance. 



METHOD OF HOFFMANN AND FICKER. Hoffmann 

 and Ficker l published a method for the isolation of bacil- 

 lus typhosus from infected waters, which consists in the 

 addition of increasing quantities of caffein, crystal violet, 

 and nutrose to large quantities of the water. They add 1 

 per cent, of nutrose, 0.5 per cent, of caffein, and 1 per 

 cent, of a 1 to 1000 solution of crystal violet to the 

 water and incubate at 37 C. for twelve to thirteen hours. 

 In this manner they reduce the number of water bacteria, 

 while bacillus typhosus increases in numbers. The three 

 solutions to be added to the water are prepared as follows : 



1. A solution of 10 grammes nutrose in 80 c.c. of 

 distilled water. The solution is placed in a water-bath 

 for several hours and is not filtered. 



2. A solution of 5 grammes of caffein in 20 c.c. of 

 warm (80 C.), sterile distilled water. The solution is 

 to be freshly prepared and should not be shaken. 



3. A solution of 0.1 gramme of crystal violet in 100 

 c.c. of sterile distilled water. This must be freshly 

 prepared each time. 



900 c.c. of the water to be examined are placed in a 

 flask and the three solutions are added, and the mixture 

 thoroughly shaken. After incubation, the water is exam- 

 ined according to several well-known methods. For 

 instance, some of the supernatant portion of the fluid 

 is removed and spread out in a thin layer upon plates 

 made with Drigalski-Gonradi agar, or 500 c.c. of the 

 water may be precipitated with typhoid immune serum 

 according to the method of Altschuler and incubated 

 again for three hours and then plated, or 500 c.c. may 

 be precipitated by the chemical-mechanical method of 



