BACTERIOLOGICAL TECHNIQUE 27 



contradistinction to those which thrive in presence of oxygen 

 or air. In order to cultivate such bacteria it is necessary to 

 remove the oxygen from above the medium ; this can be 

 done most simply by enclosing the culture tube in a larger 

 tube (Fig. 5 c) or receptacle containing alkaline pyrogallate 

 of soda, which has the property of rapidly absorbing oxygen. 

 An even simpler method is to fill the tuBe nearly to the top 

 with medium, and after inoculation to fill up the remaining 

 space with vaseline. 



Culture Media for Yeasts. In the case of yeasts, wort 

 gelatine is a more suitable medium than ordinary nutrient 

 gelatine ; in this case, instead of bouillon, boiled hot wort, 

 obtainable from a brewery, may be used advantageously; 

 the wort should be diluted with water to a specific gravity of 

 about 1050. The wort must be filtered until it is quite bright, 

 and should remain free from deposit after sterilisation. To 

 prepare wort gelatine 100 grammes of gelatine are added to a 

 litre of the wort and the whole clarified, filtered and sterilised 

 in the same manner as ordinary G.P.B. 



Culture Medium for Moulds. Moulds will grow on nearly 



all the media so far considered. A solution specially suited 



for their development is known as Raulin's solution. It is 

 prepared as follows : 



Water . . . . . . 1500 grammes 



Cane-sugar . . . . . . 70 



Tartaric acid .- . . . . 4 



Ammonium phosphate . . 0*60 



Magnesium carbonate . . 0'40 



Ammonium sulphate . . 0*25 



Zinc sulphate . . . . 0'07 



Ferrous sulphate . . . . 0*07 



Potassium silicate . . . . 0'07 



To prepare a Pure Culture of Bacteria. In transferring 



