Of the serious corneal ulcers the most frequent are those due to pneumococci, while next in frequency of occurrence are those due to diplobacilli. The characteristics of the pneumococcus ulcer, or ulcus serpens, are so well known that it is not necessary to discuss them here at length, but it may be well to emphasize certain features. Undoubtedly the most common cause for this type of ulcer is trauma, but there are two other causes that are often not recognized, namely, herpes corneae and glaucoma. Peters,1 in fact, insists that the peculiar character of ulcus serpens is dependent on a neuropathic basis. This I think is doubtful, but it is probable that in many cases corneal herpes permits the pneumococcus infection to take place. After the infection has become well established the herpetic condition is obscured and so escapes recognition. The course of these cases, however, usually seems to