20 



KAN-ICHIRO MORISHIMA 



tral lead acetate in sterile distilled water is prepared and heated 

 for one- half hour at 100°C. in a water bath. Five cubic centi- 

 meters of the solution is added to 100 cc. of the agar, melted 

 and cooled to about 60°C. This lead acetate agar is trans- 

 ferred to small test tubes to a depth of about 1.5 cc. If the 

 agar with the lead acetate is tubed while hot, a precipitate con- 

 taining most of the lead settles to the bottom of the tube; this 

 may be prevented by cooling the agar to 60° or 70°C. before 

 tubing it. 



A 1 per cent stock solution of china blue in distilled water is 

 kept on hand. Four-tenths of a cubic centimeter of normal 

 sodium hydrate are added to 10 cc. of the china blue solution, 

 and the mixture is heated on the water bath for ten minutes at 

 100°C. The color changes from blue to brown during the heat- 

 ing. One and one-fifth cubic centimeters of this decolorized 

 china blue solution is added to 100 cc. of nutrient agar of reac- 

 tion, — 0.2 to —0.4. One per cent lactose and 0.1 per cent glucose 

 are added and the mixture is heated ten minutes in the water 

 bath at 100°C. The medium is cooled to about 60°C, and is 

 then ready to be added as a second layer to the small tubes 

 containing the lead acetate agar. It forms a layer of about the 

 same depth as the latter medium. The tubes are incubated 

 overnight, and any contaminated ones are discarded. 



The results of stab cultures in this medium after ten to eight- 

 een hours' incubation may be summarized as follows: 



CULTURE 



B. typhosus 



B. paratyphosus A. 

 B. paratyphosus B. 



B. enterilidis 



B. coll 



GAS PRODUCTION 



+ 



+ 



+ 



+ + 



BOTTOM LAYER 



Black 

 No change 

 Black 

 Black 



Black, or no 

 change 



TOP LAYER 



Pale blue 

 Pale blue 

 Colorless 

 Colorless 

 Deep blue 



It is thus seen at a glance on the morning after the suspicious 

 colony is fished, whether the organism is B. paratyphosus A or 

 B, the typhoid bacillus, or B. coli. The medium does not differ- 

 entiate between B. paratyphosus B and B. enteritidis. By in- 



