164 



CULTURE MEDIA 



piece of clean filter paper and add to the water in the flask. 

 Shake the flask well to make an even emulsion of the meat 

 extract. 



3. Weigh out Witte's peptone (10 grammes), salt (5 grammes). 

 Mix into smooth paste with 100 c.c. distilled water previously 

 heated to 60 C. 



5. Add the peptone salt emulsion to the meat extract emulsion 

 in the flask and add 650 c.c. distilled water. Heat in the steamer 

 for forty-five minutes. 



6. Standardise the medium and complete as for nutrient 

 bouillon. 



Nutrient Gelatine. 



i. Weigh a 2 -litre flask on a trip balance (Fig. 106) 

 and note the weight, or counterpoise carefully. 



FIG. 1 06. Trip balance. 



An extremely useful counterpoise is a small sheet- 

 brass cylinder about 38 mm. high and 38 mm. in di- 



u 



^ ' ^ 



FIG. 107. Counterpoise; weight when empty, 35 grammes; when full of dust 

 shot, 200 grammes. 



ameter, with a funnel-shaped top and provided with a 

 side tube by which its contents, fine "dust" shot, may 

 be emptied out (Fig. 107). 



