NUTRIENT CULTURE-MEDIA 7 1 



Nitrate Broth. One gram peptone to one liter water and 



add 0.2 gm. nitrite free potassium nitrate; place ten 



c.c. in test-tube, sterilize in autoclave. 

 Nutrient Broth. i. Cover i pound (500 gm.) chopped 



meat with 1000 c.c. water and place in refrigerator 



twelve hours. 



2. Strain through Canton-flannel or cheese-cloth and 

 add water to make 1000 c.c. 



3. Add i per cent, peptone, warming until dissolved. 



4. Heat over water-bath thirty minutes. 



5. Restore loss of water. 



6. Titrate and adjust reaction to +i per cent, by 

 adding alkali or acid. (See above.) 



7. Boil two minutes over free flame. 



8. Restore loss of evaporation. 



9. Filter through absorbent cotton and Canton-flannel 

 and refilter until clear. 



10. Titrate and record final reaction. If it varies 0.2 

 per cent, from standard, readjust. 



11. Tube, using 10 c.c. in each tube. 



12. Sterilize. 



The nutrient broth as above prepared is used as a basis 

 for most of the other media. It is practically the same 

 as was devised by Loffler in the early days of bacteri- 

 ology. 



Sugar Broths. Prepared as the standard broth with the 

 addition of i per cent, dextrose, lactose, or other sugar 

 just before final sterilization. 



Nutrient Gelatin. Ten per cent, gelatin is added with the 

 peptone to the meat-water infusion. Warm gently at 

 60 C. until dissolved, then adjust reaction. Heat 

 over steam-bath for forty minutes. Restore loss of 

 evaporation, readjust reaction, and boil five minutes. 

 Make up loss from evaporation and record final reaction. 

 Filter, tube, and sterilize fifteen minutes in autoclave at 

 120 C. Place at once in ice- water until solid and store 

 in ice-chest. 



Nutrient Agar. Boil 10 to 15 gm. thread agar in 500 c.c. 



