BACTERIOLOGICAL TECHNIC 35 



Hesse's medium — 



Agar S grams 



Pepton lo grams 



Extract of meat 5 grams 



NaCl ~ 8.S grams 



Distilled water 1,000 c.c. 



Capaldi's medium — 



Pepton 20 grams 



Gelatin 10 grams 



Agar 20 grams 



Dextrose or mannit 10 grams 



NaCl 5 grams 



KCl 5 grams 



Distilled water 1,000 c.c. 



Malachite green media. — ^Two to 3 c.c. of a 2 per 

 cent solution of "Hochst 120" malachite green solu- 

 tion is added to broth (alkaline to litmus). 



Ox-bile medium. — ^This culture medium is used for 

 the detection of B. coli in water. Dissolve i per cent 

 lactose and i per cent pepton in fresh ox bile, filter and 

 fill in fermentation tubes and sterilize in the arnold for 

 three successive days. 



EXERCISE 13. PREPARATION OF MEDIA FOR WATER 

 AND MILK EXAMINATION 



Litmus solution. — ^Dissolve i part Merck's pure 

 extract of litmus in 100 parts of water, filter, and 

 sterilize in the autoclave for 5 minutes at 120° C. 



Litmus lactose agar and litmus dextrose agar. — 

 Dissolve I per cent lactose or dextrose in sugar-free 

 agar. The litmus should be added in the petri dish 

 before use from a sterile tube of litmus solution by 

 means of a sterile i c.c. pipette. 



