In a previous communication1 about blindness in Guernsey calves, one of us (the senior author) reviewed the literature of this subject, discussed the clinical symptoms of the disorder and recorded the results of an investigation of its pathologic histology. The chief facts and observations developed by this study, briefly summarized, are as follows : A disease which may be regarded as a clinical entity, well known to veterinarians and others concerned with the care of cattle, but to which comparatively few publications have been devoted, apparently first carefully described from the general and pathologic standpoints thirty years ago by Nettleship and Hudson, characterized by complete blindness and papilledema (choked disk) and practically unassociated with other symptoms, exists among calves (male and female), usually, if not exclusively, of the Guernsey breed, and is generally detected within the first year of life, but may be present at birth. The important pathologic