The growth of the typhoid bacillus on an agar-medium containing 10 per cent. defibrinated rabbit blood, which we have found of advantage in our experiments, differs in certain respects from the growth on plain agar. We have already noted that the blood-agar cultures are more abundant. A concrete example of the amount of growth produced on each medium may be drawn from certain of our vaccine preparations to be more fully described later. To produce growths of Bacillus typhosus for immunizing vaccines we inoculate one-quart Blake bottles containing 100 c.c. of medium with a few cubic centimeters of a twenty-four-hour bouillon-culture of the organism. In one experiment nine Blake bottles of 2 per cent. agar were inoculated with a plain bouillon-culture of B. typhosus No. 3; at the same time, nine Blake bottles of 10 per cent, blood-agar were inoculated with a blood-bouillon culture of B. typhosus No.