62 THE BACTERIOLOGICAL EXAMLNATION OF MILK 



taken up on the point of the platinum needle, a test tube contain- 

 ing from 30 to 40 c.c, of tap water at room temperature. Repeat 

 this until the water shows a slight turbidity, and set aside for 

 half an hour or longer ; do not shake or handle the tube 

 roughly. 



3. With a finely drawn pipette, take up a small quantity of the 

 surface water from the inoculated tube, and distribute it in small 



droplets upon the slide, as 

 shown on Fig. 9. 



4. Place aside to dry, 

 carefully covered from 

 chance of dust. When 

 dry, the staining can be 

 proceeded with according 



Fig. q. — Slide prepared for flagella staining. . . i. iU j j ^ j 



^ ^ ^ ^ * to the method adopted. 



Do not fix the films in the flame ; the flagella are apt to be 

 injured thereby, and it will be found that the subsequent mani- 

 pulations will cause the organisms to adhere sufficiently to the 

 slide. 



Staining the Film 

 The three ordinary methods practised in this country are : — 



( I ) Pitfield's method {Mtiir's modification). 

 The following solutions are required : — 



A. The Mordant. 



Tannic acid, lo per cent, aqueous solution . . .10 c.c. 



Corrosive sublimate, saturated aqueous solution . . 5 c.c. 



Alum, saturated aqueous solution ... .5 c.c. 



Carbol-fuchsin (Ziehl) . . . . . . 5 c c. 



The above must be thoroughly mixed, and the precipitate which forms must 

 be allowed to deposit. The clear supernatant fluid is then drawn off with a 

 pipette and placed in a clean dropping bottle. The mordant will remain good 

 for one or two weeks, but not longer. 



B. The Stain. 



Alum, saturated aqueous solution . . . .10 c.c. 



Gentian violet, saturated alcoholic solution . . . 2 c.c. 



Filter twice. The stain must be freshly prepared and will not keep. 



The film is prepared as described above. The mordant is then dropped on 

 to the slide and heated gently over the flame until the steam begins to rise. 

 Allow to steam for from one to two minutes, wash well in running water and 

 dry carefully. When thoroughly dry apply a sufficient quantity of the stain, 



