Among the cardiovascular diseases which have been morphologically described as allergic inflammations, some have their main lesions in the adventitia, some in the endocardium, and some in the interstitial connective comparatively selectively. It is a matter of course that the thought of the affinity of antigen to each tissue has been brought in.Prof. AMANO, in his " Fundamentals of Hematology "'l)> ( 4 e ) classified antigen-antibody reaction into histiotropic and serotropic reactions, from his theory on functions of the plasma cell system and the histiocyte system. Accordingly, he stated that there were two kinds of antigens; the antigen which produces histiotropic antigen-antibody reaction, and the antigen which produces serotropic antigen-antibody reaction. Likewise, antigen-antibody reactions in cardiovascular diseases of the allergic origin are divided into two, from the view-point of site where the reactions take place. One is intravascular antigen-antibody reaction and the other is extravascular antigen-antibody reaction"l'.Histological changes in these reactions were investigated.One of the intravascular allergic inflammations is the so-called Intrakapillare Glomerulonephritis " of FAHR'*), in which pathological changes of glomerulonephritis occur in the lumens of glomerular capillaries. This opinion was supported by MASUGI'~), ALLEN'" and FISHBERG"". This concept, however, is based on the site of the histological changes, and not on the site of the reaction itself. Recent advance in immuno-hematology has disclosed such diseases as acquired hemolytic in which antibody against one's own red blood cell is present in his serum. In these cases antigen-antibody reaction may occur in the vessels. Experimental studies are naturally required for histological investigation in these cases.BAN'" chose red blood cell as the most suitable antigen to produce anemia' a e ) ,