FUCHSIN A GAR 



20 5 



the calculated medium figure (in this case 1031.5 grammes) by 

 the addition of distilled water at 100 C. 



7. Clarify with egg and filter. 



8. Tube and sterilise as for nutrient agar. 



Bile Salt Agar (MacConkey). 



1. Weigh out powdered agar, 15 grammes (= 1.5. per cent.)* 

 and emulsify with 200 c.c. cold tap water. 



2. Weigh out peptone, 20 grammes ( = 2 per cent.) , and emulsify 

 with 200 c.c. tap water previously warmed to 60 C. 



3. Mix the peptone and agar emulsions thoroughly. 



4. Weigh out sodium taurocholate, 5 grammes ( = 0.5 per 

 cent.), dissolve it in 300 c.c. tap water, and use the solution 

 to wash the agar-peptone emulsion into a tared 2-litre flask. 



5. Bubble live steam through the mixture for twenty minutes. 



6. Adjust the weight of the medium mass to the calculated 

 figure for one litre (1040 grammes). 



7. Cool to 60 C. and clarify with egg as for nutrient agar 

 (vide page 168). 



8. Filter through papier Chardin, using the hot-water funnel. 



9. Weigh out lactose, 10 grammes (= i per cent.), and dissolve 

 it in the agar. 



If desired, add 5 c.c. of a i per cent. ( = 0.5 per cent.) aqueous 

 solution of neutral red. 

 10. Tube, and sterilise as for nutrient agar. 



Litmus Nutrose Agar (Drigalski=Conradi). 



This medium should be prepared in precisely the same manner 

 as the Nutrose agar described .on page 172 substituting meat ex- 

 tract for serum water, and increasing the percentage of agar added 

 per litre to 3 per cent. 



Fuchsin Agar (Braun). 



1. Liquefy and measure out into a sterile flask: 



Nutrient agar 1000 c.c. 



2. Weigh out: lactose 10 grammes and dissolve in the fluid 

 agar. 



3. Adjust the reaction to 5 and filter. 



4. Measure out and mix thoroughly with agar: 



Fuchsin, alcoholic solution 5 c.c. 



The fuchsin solution is prepared by mixing: 



Fuchsin (basic) 3 grammes. 



Absolute alcohol 60 c.c. 



Allow to stand twenty-four hours, then centrifugalise 

 thoroughly and decant the supernatant fluid into a 

 well-stoppered bottle, j 



