164 APPENDIX 



The mixture is tubed and sterilized in current steam, twenty 

 minutes each day. 



To avoid decomposition of the sugar-alcohols such media 

 must never be heated above 100 C. and should be heated as 

 little as possible. 



Fresh-meat infusions must not be used in the preparation of 

 sugar media, since they usually contain inosite, etc. Great care 

 must be taken to ensure the purity of the substances to be tested 

 for fermentation. 



Sugar-alcohol media for the differentiation of streptococci. A 

 stock solution is made up containing Lemco 10 grammes, peptone 

 10 grammes, sodium bicarbonate I gramme, 10 per cent, aqueous 

 litmus-solution 100 c.c., distilled water to I litre. This is boiled 

 and filtered in the ordinary way. One per cent, of the sugar, 

 alcohol or glucoside is added to portions of this stock solution 

 to make the different media. The tubes are sterilized in current 

 steam for half an hour for three successive days. 



The sugar-alcohol substances recommended by Gordon are 

 lactose, saccharose, salicin, mannite, raffinose and inulin. 



No double tubes are required since the presence of acid only, 

 not gas and acid, is recorded. To enable this to be accurately 

 done it is important that the same colour tint with litmus should 

 be produced for each batch. It is also convenient to use a sterile 

 control tube when comparing colour production. 



Lactose Bile Salt Broth. 



Sodium taurocholate ... ... 5 grammes. 



Lactose ... ... ... ... 5 



Peptone ... ... ... ... 20 



Water 1000 c.c. 



These constituents are heated together until the solids are 

 dissolved. The mixture is filtered, and sufficient neutral litmus 

 solution is added to give a distinct colour. The medium is then 

 distributed into Durham's fermentation tubes and sterilized by 

 steaming for twenty minutes on three successive days. 



The sodium taurocholate prevents the growth of many 

 saprophytic bacteria. 



