196 SPECIAL MEDIA 



2. Add 



Hydrochloric acid (or glacial acetic acid) . 1.5 c.c. 

 and boil. 



3. Filter off coagulated casein. 



4. Neutralise to litmus by the addition of 3 caustic soda so- 

 lution and boil. Whey now cloudy and acid again. 



5. Again neutralise to litmus by addition of ^L caustic soda 

 solution. 



6. Filter. 



7. Tint the whey with neutral litmus solution to a deep purple 

 colour. 



8. Tube and sterilise as for milk. 



Litmus Whey Gelatine. 



1. Measure out milk 1000 c.c. into a tared 2-litre flask. 



2. Add hydrochloric acid (or glacial acetic acid) 1.5 c.c. and 

 boil for five minutes. 



3. Filter off the casein, and make the whey faintly alkaline to 

 litmus. 



4. Weight out 



Peptone 10 grammes 



and emulsify in a few cubic centimeters of the whey and return 

 to the flask. 



5. Weight out 



Gelatine 50 grammes 



add it to the whey in the flask and incorporate the mixture 

 by bubbling through live steam. 



6. Clear with egg and filter. 



7. Make the weight of the medium mass to the calculated fig- 

 ure for one litre (1060 grammes) by the addition of distilled water. 



8. Weigh out 



Dextrose 15 grammes 



and dissolve in the fluid whey gelatine. 



9. Add sterile litmus solution to the required tint. 



10. Tube and sterilise for twenty minutes in steamer at 100 C. 

 on each of five successive days. 



This medium will remain semi-fluid at the room temperature, 

 and may be used for cultures in the cool or hot incubator. 



Litmus Whey Agar is prepared in a similar manner to Whey 

 Gelatine, with the substitution of 15 grammes of agar for the 

 gelatine. 



Malt Extract Solution (Herschell). 



1. Measure into a flask distilled water 1000 c.o. 



2. Weigh out 



Extractum malti (malt extract) . . 25 grammes 

 and add to distilled water in flask. 



