488 APPENDIX 



To Clean Glass Apparatus 



Test-tubes and flash may be washed in a bucket with hot water and 

 soap powder or soda, or boiled in the same. They should then be 

 cleaned with test-tube brushes and inverted for draining. Before use 

 they must be sterilised. Pipettes may be treated in the same way, and 

 then rinsed through with rectified spirit, and sterilised in the hot-air 

 oven. When test-tubes and pipettes are infected, they should be 

 treated in a similar manner, and also placed in strong disinfectant or 

 nitric acid (5 per cent.). Greasy slides should be placed in alcohol and 

 acid (5 per cent. HCl or HgSOJ for several hours, and then rinsed in 

 water. Greasy cover-slips may be treated in the same way, or boiled 

 in chromic acid (10 per cent.) and washed in acid alcohol and water. 



Choice of Medium 



This must be left very largely to individual experience and the 

 objects of the investigation. In a general way the constituents of the 

 various media described indicate the purposes to be obtained. The 

 general standard liquid media are bouillon and milk, the. solid media are 

 gelatine (for room temperature cultivation) and agar (for blood-heat). In 

 tropical countries a combination of the two may be used. Further, 

 just as gelatine is a solid bouillon, so gelatinised milk may be used when 

 a solid milk medium is required. For anaerobes glucose and formate 

 media are commonly used. There are, of course, various media used for 

 different species of organisms. For the streptothrix group including B. 

 tuberculosis, glycerine media and potato are used. To isolate the B. typhosus, 

 carholised media and Eisner are taken^ Chromogenic bacteria nearly 

 always grow well on potato. The use of litmus milk, beer wort, wort 

 gelatine, milk agar, etc., is sufficiently designated in the names of the 

 media. 



Preservation of Media. — Media may be kept in good condition for 

 months if a few simple precautions are borne in mind. The tubes or 

 flasks containing the medium must be effectually sealed, either with caps, 

 corks, or paraffin. The store of media must then be kept in a closed 

 metal box, and in a cool dark place. 



