In a previous article (1) we have shown that there exist between antisera and antigens of liver or kidney certain distinguishing reactions which apparently indicate the existence of a definite biological difference between these two organs. This difference was demonstrated by either cross fixation or by fixation following absorption of the sera by the respective homologous and various other organ cells. We purposely avoided the use of the term specificity because we considered it essential to extend our investigation to include other organs before we might consider the differences noted as definite evidences of tissue specificity. We also noted in our experiments that both the antigens and the antisera were apparently rather complex and appeared to contain at least three distinct partial antigens or antibodies. The first of these antigens had apparently a wide range of activity and presumably possessed a relationship to all organs of the species.