1) In case of antiserm as the antigen of bovine serum and its serum protein fractions, the quantity of preciptin seems to be increased more with addition to a number of injection and with this fact appears the non specific side reaction. Of the side reaction, the lamb serum reacts less strongly than bovine serum, the chief antigen because of the closeness of the zoological relationship; the serums of swine, horse and human react less strongly than the lamb serum. And it has been noticed that these antiserum are difference with one another in their side reaction. 2) The increase of side reaction and quantity of precipitin can be confirmed the difference in case of immunized injections once and three times, but not in case of five and times. The chief precipitin titer becomes the highest in case of immunized injection five times bnt afterwards it does not get high remarkably according to the increase of times of immunized injection. 3) The side precipitin titer and quantity are always lower than that of chief according to the repeated injection used as an antigen, there are difficult to be distinct the chief and side reaction with only precipitin titer, however are clearly distinct with precipitin quantity. 4) Immunized with bovine serum protein fractions, the antigenity is higher than that of bovine serum itself. And antigenity of albumin is not less than that of other patterns and race speciality is intensive. 5) The substance of the non specific side reaction in case of antigen of injected bovine serum exisits in the protein which to the euglbulin and pseudoglobulin frsctions, and seems to be more in pseudoglobulin. 6) The side reaction appears more clearly, according to the increase of chief precipitin quantity in case of the antiserum of the same soecies, and according to the increase of the frequency of the occurrence of the complex stair-like "form of reaction field" in the case of the antiserum that has the same precipitin quantity.