In the course of a systematic study of the modes of ingress and egress of the various components of the intra-ocular fluid it seemed desirable to include a study of the intra-ocular exchange of gases, with particular reference to oxygen and carbon dioxide. The previous data in this field are limited to those obtained in the study of the gas content of the aqueous by de Haan1and in that of the permeability of the cornea to gases by F. P. Fischer.2These two important studies do not, however, give an adequate picture of the movement of gases into and out of the intra-ocular fluid. The general plan of experiment which we have adopted consists in replacing a measured volume of aqueous by a bubble of gas—either air or nitrogen—and removing samples of the bubbles of gas at varying intervals in different experiments. The course of events in