S. paratyphi B with V antigen and its variant without V antigen formed different colonies on the 1.5% agar plate containing anti-V factor serum, and S. paratyphi A with I antigen and its variant without I antigen also formed different colonies on the 1.5% agar plate containing anti-I factor serum. Namely V⁺ and I⁺ bacilli formed respectively small, convex and thick colonies and V^- and I^- bacilli formed respectively large, flat and thin colonies. Consequently we can use this method to see whether the bacterium lost antigen or not. And we consider that on the semisolid agar plate with antisera added those which had the antigen formed small colonies, their motility being inhibited, and those which lost the antigen formed large colonies, their motility being uninhibited.

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We demonstrated a second example of anti-I antibody as an incomplete antibody in the serum of a mother who delivered erythroblastotic infants. The agglutinin titer of this antibody against her husband's trypsinized red cells was 128 units.

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The titer of the group specific isoagglutinins in human normal serum has a hereditary nature. Examination of different families showed that higher titer tends to be inherited recessively to the lower.

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