202 SPECIAL MEDIA 



6. Add 10 c.c. sterile neutral red, i per cent! aqueous solution. 



7. Tube in quantities of 10 c.c., slant, and allow to set. 



8. Incubate for forty-eight hours at 37 C. and reject any 

 contaminated tubes. Store the sterile tubes for future use. 



Coli-typhoid Group. 

 Parietti's Bouillon. 



1. Measure out pure hydrochloric acid, 4 c.c., and add to it 

 carbolic acid solution (5 per cent.), 100 c.c. Allow the solution 

 to stand at least a few days before use. 



2. This solution is added in quantities of o.i, 0.2. and 0.3 c.c. 

 (delivered by means of a sterile graduated pipette) to tubes each 

 containing 10 c.c. of previously sterilised nutrient bouillon (vide 

 page 163). 



3. Incubate at 37 C. for forty-eight hours to eliminate con- 

 taminated tubes. Store the remainder for future use. 



Carbolised Bouillon. 



1. Prepare nutrient bouillon (vide page 163, sections i to 6). 

 Measure out 1000 c.c. 



2. Weigh out carbolic acid, i gramme (2 . 5 or 5 grammes may 

 be needed for special purposes), and dissolve it in the medium. 



3. Tube, and sterilise as for bouillon. 



Carbolised Gelatine. 



1. Prepare nutrient gelatine (vide page 164, sections i to 7). 

 Measure out 1000 c.c. 



2. Weigh out carbolic acid, 5 grammes ( = 0.5 per cent.), and 

 dissolve it in the gelatine. 



3. Filter if necessary through papier Chardin. 



4. Tube, and sterilise as for nutrient gelatine. 



One or 2 . 5 grammes of carbolic acid ( = 0.1 per cent, or 0.25 

 per cent.) are occasionally used in place of the 5 grammes to meet 

 special requirements. 



Carbolised Agar. 



1. Prepare nutrient agar (vide page 167, sections i to 8). 

 Measure out 1000 c.c. 



2 . Weigh out i gramme pure phenol and dissolve in the medium. 



3. Filter if necessary through papier chardin. 



4. Tube, and sterilise as for nutrient agar. 



Litmus Gelatine. 



1. Prepare nutrient gelatine (vide page 164, sections i to 8). 



2. Add sterile litmus solution, sufficient to tint the medium a 

 deep lavender colour. 



3. Tube, and sterilise as for nutrient gelatine. 



