With the increasing use of corneal transplants for therapeutic or functional reasons, the importance of immunological aspects becomes increasingly evident. In this regard perhaps the major problem is the phenomenon of "late clouding." A technically successful, clear graft may frequently become opaque after a period of three to four weeks of perfect transparency. This delayed opacification is the cause of many failures in keratoplasty. There are still many unanswered questions in regard to corneal antigenicity and, in particular, with its relationship to the different anatomical structures of the cornea. The purpose of this study was, therefore, to determine, if possible, the antigenicity of the individual corneal layers separately. As early as 1914, anaphylactic reaction was suggested by Underwood1as being the cause of the destruction of donor material in a case of skin homotransplants. A similar suggestion was also made by Holman,2but, in addition, he noticed that