THE PRESERVATION of ocular tissues in a living state outside the human body is of interest because such tissues may support the growth of viruses affecting the eye and their mode of action and propagation can be studied. Some viruses have been successfully cultivated in animals or in the developing chick embryo (those of herpes simplex, vaccinia, lymphogranuloma venereum, epidemic keratoconjunctivitis) ; others, such as the viruses of trachoma and inclusion conjunctivitis, have up to now not been grown with certainty outside the human body. This study deals with experiments in a large series of mammalian ocular tissues transplanted and kept viable on the chorioallantoic membrane of the developing chick embryo and the infection of such transplants with pathogenic ocular viruses. MATERIALS AND METHODS In 1912 Murphy1successfully grafted mammalian tumor tissues onto the chick embryo. Since then a number of normal and tumor tissues from different species have been