After removing a circular area of the central corneal epithelium of the rat eye, the labelling indices and the mitotic rates were measured at various times after wounding, both in the cornea and in the adjacent conjunctival epithelium. The proliferative response was most marked in the corneal epithelium adjacent to the wound, but there was also a definite response in the epithelium covering the denuded areas, and in the conjunctival epithelium. The study demonstrated that the conjunctival epithelium. The study demonstrated that the conjunctiva itself plays a role in the healing of a central corneal epithelial wound. The similarities in the cellular response may indicate that both epithelia are under the influence of the same growth-suppressing factors (chalones), and must be looked upon as a unit. However, no support was found for the theory that the limbal area serves as a generative organ for the corneal epithelium.

The migration of cells in the rat corneal epithelium was studied using continuous labelling with tritiated thymidine [3H]TdR, during a 24 h period. Most mitoses resulted in 2 new basal cells. Cells leaving the basal cell layer moved vertically to the surface in all areas of the corneal epithelium. The first labelled cells reached the surface 3 days after the first injection of [3H]TdR. No stream of cells from the conjunctiva to the cornea in the limbal areas was observed, and no centripetal migration of epithelial cells in the cornea could be observed. After a cell has lost its attachment to the basement membrane, it is committed to be exfoliated in a few days without undergoing mitosis. Thus the slow centripetal migration of epithelial cells and the exchange of centrally located cells, as indicated by clinical findings and experimental studies, can only be explained by migration of basal cells.

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A stathmokinetic method to study the mitotic rate in the corneal epithelium of the rat is described and applied. Horizontal and vertical diameter sections were used. In order to analyze the mitotic rate in the various parts of the corneal epithelium, each vision field (objective 100, eye piece 12.5), comprising 182 microns basement membrane, was regarded as a separate unit. Since the number of vision fields across the cornea varies from specimen to specimen, we constructed a mathematical method to correlate corresponding corneal areas from different eyes. Using this method it is shown that the mitotic rate is almost equal all over the cornea, with no definite reduction in the central areas. There is no area of significantly high proliferation rate, either in the limbal area or in the adjacent conjunctiva.