Two of the existing concepts of the function of blood vessels in corneal tissues are diametrically opposed. According to the first, the one generally held, the function of the vessels is reparative; according to the second, it is destructive. Growth of blood vessels regularly accompanies healing throughout the body ; repair and vascularization go hand in hand in practically all inflammatory processes. A well marked interstitial keratitis rarely shows any regression until from four to eight weeks after the onset, at the time when stromal vessels become visible. The same is true of many other corneal inflammations. For instance, some deep herpetic infections fail to subside for many weeks or even months. During this period of time blood vessels have made their appearance in the corneal stroma, and when healing does occur it is likely to be attributed to the increased vascularity. On the other hand, the clinical course of a