The production and the specificity of hemogeneous organic antibody were investigated by the precipitation test in the agar layer. And the results were as follows. 1. Sensitizing the homogeneous animal (rabbit) by the homogeneous (rabbit) organic (liver, kidney or spleen) antigen, the substance corresponding to the above organic antigen was identified in the sensitized rabbit's blood and the precipitation band was clearly found by the precipitation test of Oudin's method in the agar layer. And the production of antibody by the extracted antigen of homogeneous organ with physiological salt solution was certified. 2. Sensitizing by the organic antigen, the precipitation band appeared most remarkably around the 4 th week after the sensitization. 3. There were both of antigen excess zone and antibody excess zone and the precipitation band was clearly separated on the use of liver antigen in dilution of 16 times, kidney and spleen antigen in dilution of 8 times and antiserum in dilution of 8 times, when the organic antibody of 40% was used as the original solution. 4. In the cases sensitized by the organic antigen, the migration velocity of precipitation band was proportional to the squar root of time after the accumulation. 5. Carrying out the Oudin's precipitation test in the agar layer on the use of the liver, kidney and spleen antigen of homogeneous and heterogeneous animals, the number of the appeared precipitation band was much in th cases sensitized by the homogeneous antigen than that in the cases sensitized by the heterogeneous antigen. As for the antigen-antibody reaction among the organs in the same system, the precipitation band appeared more numerous on the antigen-antibody reaction among the homogeneous organs than that on the antigen-antibody reaction among the heterogeneous organs and the relative specificity of organic antigen was observed. On the other hand, the number of precipitation band appeared at that time was 3-4 in the cases sensitized by the liver antigen, 2-3 in the cases sensitized by kidney and spleen antigen. In other words, the number of precipitation band showed more numerous in the cases sensitized by the liver antigen than other cases. 6. The reaction of each antigen with the antibody corresponding to each antigen was observed on the cases sensitized by each organ and the appeared state of precipitation band was also hourly observed. The precipitation band appeared the most remarkable around the 3 rd. week after the end of sensitization and the precipitation band corresponding to the organic antigen appeared more early in the cases sensitized by the spleen antigen than that in the cases sensitized by other organic antigen. Moreover, It was seen that the disappeared precipitation band appeared again after several weeks or the number of precipitation band increased after several weeks. 7. On the sensitization of rabbit by the phosphatid, extracted from each organ, with the addition of neat serum, it's antiserum showed more precipitant band to it's organic phosphatid than that to each organic phosphatid, and the organic antigen relatively showed the specificity. 8. Studying on the precipitation band by the immuno-electrophoresis, it appeared 6-7 in the cases sensitized by the rabbit's liver antigen and 5-6 in the cases sensitized by the rabbit's kidney and spleen antigen. On the other hand, the precipitation band appeared 3 by the method in the cases sensitized by each organic antigen of rabbit's liver, kidney and spleen
