166 APPENDIX 



duplitest paper, and made alkaline with sterile soda solution 

 until the red slip is red-violet. To 100 c.c. of the hot agar 

 I c.c. of a I : 60 solution of malachite green in distilled water 

 (the solution keeps good for ten days) is added i.e., the agar 

 contains I : 6000. 



The finished agar is poured at once into Petri-dishes in 

 layers 2 millimetres thick. The dishes are well dried, and 

 can be kept in the ice-chest. 



By this strength of malachite green the growth of most 

 kinds of B. coli, as well as of many alkali-forming organisms, 

 is greatly diminished. The B. typhosus colonies are also retarded, 

 but can be recognised, the size of a grain of sand, with the 

 naked eye after twenty-four hours ; after a longer period (two to 

 four days) larger, better developed colonies appear, which colour 

 the agar yellow. 



Dulcite Malachite Green Broth. Liebig's Extract, 10 grammes; 

 peptone, 10 grammes ; sodium chloride, 5 grammes, are boiled 

 up with a litre of distilled water. The mixture, after filtration, 

 is made up accurately to a 4- I per cent, reaction, and 5 grammes 

 of dulcite are added ; O'5 gramme of powdered malachite green 

 is very accurately weighed out, and also added. The mixture, 

 usually slightly turbid, is steamed for thirty minutes, and again 

 filtered. It is tubed, 10 c.c. into each tube, and sterilized for 

 thirty minutes on two successive days. 



Brilliant Green Agar. Fawcus' modification. Conradi's 

 brilliant green agar has been modified by Fawcus 1 by the 

 addition of lactose and bile-salt and by increasing the percentage 

 of brilliant green. Prepared as follows : 



To 900 c.c. of tap-water add 5 grammes sodium taurocholate, 

 30 grammes powdered agar, 20 grammes Witte's peptone and 

 5 grammes sodium chloride. Dissolve in the steam sterilizer 

 for three hours. Clear with white of egg, filter through wadding 

 and bring to a reaction of -H 1*5 per cent. 



Dissolve 10 grammes of lactose in 100 c.c. of distilled water 

 and add to the melted agar. Mix well and filter through 

 Chardin paper. To each 100 c.c. of the clear bile-salt lactose 



1 Journ. Royal Army Med. Corps, 1909, XII, p. 147. 



