1) When aluminium hydroxide absorbs the bovine serum and the fractions of its serum protein, the antigen has a high precipitin titer, a low precipitin quantity, less non specific side reaction, and strong race speciality. That is, the euglobulin and pseudoglobulin fractions that are concerned in the non specific side reaction can be intensified in their race-speciality as the antigen that aluminium hydroxide absorbed these fractions. 2) When aluminium hydroxide absorbs the bovine serum protein albumin, the antigen has a high precipitin titer, a low precipitin quantity, not non specific side reaction, and the almost absolute race-speciality. The reaction to the lamb serum which is closely related to the bovine can not be excluded.