Typhoid and paratyphoid A and B can be differentiated by means of a medium consisting of a 3 per cent. agar containing 1 per cent. of inosite and 1 per cent. dextrin, using litmus as an indicator. The dextrin must be one of the lower dextrins. The typhoid ferments the dextrin with acid formation in the butt of the tube, decolorizing entirely in 24 hours with a violet slant. Paratyphoid A does not ferment either dextrin or inosite and so the butt and slant of tube both remain violet in color. Paratyphoid B ferments inosite with gas formation and so paratyphoid B decolorizes the butt of the tube with the formation of gas bubbles, while the slant remains violet in color.