122 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



connective tissue cells surrounding and invading the clot, were many lympho- 

 cytes and the capsule of the heterogenous clot was thicker than that of the 

 homoiogenous clot. However, the thickness of the connective tissue capsule 

 and the number of lymphocytes varied in different instances and even in 

 different places in the clot. Areas of partial solution also were visible and a 

 larger number of phagocytic cells was present in such heterogenous clots. 

 The latter cells, which may show a xanthoma-like tissue arrangement, are able 

 to dissolve particles of fibrin as well as the erythrocytes. Furthermore, the 

 hemolysin present in the serum of the host and active against the blood cells 

 of strange species may help in the solution of parts of the coagulum. Also, 

 polymorphonuclear leucocytes, which again are much more prominent in 

 heterogenous than in homoiogenous transplants, invade the clot and may aid 

 in its destruction. These differences in reaction against different types of clots 

 are quite definite, although the same technique was used in these various trans- 

 plantations. In principle, the reaction against all kinds of heterogenous clots is 

 about the same, although some minor quantitative differences may exist in 

 different species; thus, in the guinea pig the solution of the clot proceeded 

 somewhat more actively than in the rat and likewise the number of polymorpho- 

 nuclear leucocytes in and around the clots was somewhat greater than in the rat. 

 These experiments indicate, then, a noticeable similarity between the behavior 

 of heterogenous blood clots and heterogenous tissues. In both cases, lympho- 

 cytes as well as polymorphonuclear leucocytes participate in the reaction in 

 addition to the connective tissue, and heterotoxins are given off by nOn-living 

 material in both types of heterotransplants ; on the other hand, homiotoxins, 

 are given off only by living tissue transplants, but not to any marked degree 

 by the necrotic homoiogenous blood clots. 



By measuring the lymphocytic and leucocytic reaction in the circulating 

 blood, Blumenthal discovered not only differences between the reactions 

 against homoiogenous and heterogenous blood clots, but he found also differ- 

 ences between the reactions against autogenous and homoiogenous clots, cor- 

 responding to those found against the corresponding normal tissues, in par- 

 ticular, he noticed an early increase in lymphocytes after homoiogenous trans- 

 plantation of blood coagula. By means of this method he could show, further- 

 more, that also homoiogenous and heterogenous plasma clots may elicit the 

 typical blood cell reactions, although they appeared somewhat later than the 

 reactions following transplantation of the whole blood clot. It appears, then, 

 that the individuality differential substances are present also in fibrin, although 

 they may perhaps not be of the same kind as those present in the cells. The 

 reactions affecting the white cells in the circulating blood seem to indicate the 

 presence of substances in the blood which are carriers of the individuality 

 differentials, although they do not elicit the local homoiogenous reactions. 

 These reactions, which are called forth by fibrin and which presumably are 

 present also in fibrinogen, are not induced by injections of blood serum ; the 

 latter does not apparently possess these individuality differential substances. 

 However, it is possible that the individuality differential substances in cells 

 included in whole blood clots are the same as those present in the fibrin, but 



