In all cases of double optic neuritis a systematic and careful examination of the patients should be made. The urine and cardio-vascular system should be examined for signs of chronic interstitial nephritis; the gums should be examined for the lead line and other indications of lead poisoning should be sought for; the question of chlorosis or other “blood disease” should be considered; and the ears should be examined for signs of otitis. But when all these conditions have been excluded and when the symptoms are apparently due to a cerebral affection, there is one group of cases in which localizing brain symptoms are absent and in which the chief indications of disease are headache, double optic neuritis, and often vomiting. In most of these cases syphilis can be also excluded. A diagnosis of brain tumor is given, and the growth is thought to be situated in some region in which the localizing symptoms are at first indefinite—cerebellum, temporo-sphenoidal lobe, or prefrontal region. Such a diagnosis often proves to be correct. Localizing symptoms may develop later and a necropsy may show the accuracy of the opinion expressed. But sometimes, to the surprise of the medical man, a fatal termination does not occur; the symptoms sometimes disappear and the patient recovers, though very often impairment or loss of vision remains. The patient may continue in good health for years or for a lifetime afterwards. Most medical men who have paid much attention to cerebral diseases will have met with a case or cases of this kind. The chief object of our article is to call attention to this class of cases and to indicate the frequency of their occurrence. Nineteen out of one hundred cases of double optic neuritis with headache in the table just given could (after careful examination) be placed in this group (X.).