592 A MANUAL OF BACTERIOLOGY 



The mixture is autoclaved at 105 to 110 C. for 1^ hours, cleared 

 with a small addition of white of egg, and filtered. To the nitrate 

 1 per cent, of lactose is added. The medium is then distributed 

 into test-tubes, 10 c.c. in each, and sterilised by fifteen minutes' 

 steaming on three successive days. Plates are made and incubated 

 at 42 C. for forty-eight hours. The colonies of organisms which 

 ferment lactose with the formation of acid are surrounded with a 

 cloudiness or haze owing to the precipitation of the taurocholate. 

 Neutral-red or krystal violet may be added (proportions, see Nos. 3 

 and 6). 



(6) Conradi-Drigalski agar. Mixture A. To 1 litre of acid 

 beef broth (p. 54) add : 



Witte's peptone . . . . .10 grm. 



Nutrose 10 



Sodium chloride . . . . 5 



Steam for one hour, and add 25 grm. of powdered agaf. Steam 

 for three hours, bring to a reaction of + 10, and filter through 

 " papier Chardin." 



Mixture B. Boil for a few minutes 100 c.c. of Kubel-Tiemann's 

 litmus solution, add 15 grm. of pure powdered lactose, and boil 

 again for a few minutes. 



Add B to A, and to this mixture add 2 c.c. of a hot 10 per cent, 

 solution of anhydrous sodium carbonate and 10 c.c. of a 0-1 per cent, 

 solution of krystal violet. The medium is then tubed, 10 c.c. being 

 placed in each test-tube, and sterilised. 



In using the medium it should be employed as surface plates. 

 The required number of tubes are melted in a water-bath, and 

 their contents poured out into sterile Petrie dishes and allowed to 

 set. These sterile plates are then placed in the warm incubator 

 for an hour or so with the lids slightly tilted at one edge, so that 

 the surface of the medium may dry somewhat. The matter to 

 be plated is sufficiently diluted, and from a few drops to 0-5 c.c. 

 are run on to the surface and spread by means of a glass rod bent 

 into a flattened hook, and sterilised by boiling. On this medium 

 in forty-eight hours B. coli forms large red colonies, B. typhosus 

 and B. dy sentence small blue colonies, and streptococci small delicate 

 red colonies. Other organisms are to a large extent inhibited from 

 developing. 



(7) 8.D.8. rebipelagar (Houston). " Rebipelagar " has been 

 much used by Houston * for the isolation of B. coli. It has the 

 following composition : Agar 20 grm., taurocholate of soda 5 grm., 



1 First Rep. on Research Work, Met. Water Board, 1908. 



