After consideration of the published records and opinions, as well as the results of my own examination of insane patients, I.havé formed the following conclusions with regard to pupillary symptoms in mental diseases. 1. General paralysis presents a very large variety of pupillary phenomena, of which the most significant is the Argyll Robertson symptom. Absoluteldirigidity of the pupil is not so frequent or so significant as reflex rigidity. Most of the other symptoms may be regarded as leading up to or dependent on the development of one of those two conditions. Many cases terminate before the light reflex becomes extinct. Reappearance of the light reflex when once,it is lost, is a possible, but rare occurrence. On the whole, the more serious derangements of the iris are more frequent in the advanced stages of the disease. 2. Syphilitic insanity, if accompanied by vascular or syphilomatous disease implicating the nervous system, may present marked pupillary symptoms, which are not necessarily permanent. In the functional varieties of syphilitic insanity, pupillary symptoms are relatively slight and inconstant. 5. Alcoholic insanity, the most common of the tòxic psychoses, is often accompanied by disturbance of the pupils. In rare cases the pupil may not react to light; sometimes the sensory reflex is absent. Sluggishness of the light reflex or of all the reactions is not uncommon; irregularity and anisocoria are fairly frequent. All these symptoms may be subject to change. 4. Insanity with epilepsy presents well -marked pupillary symptoms in association with seizures; but the pupils of epileptics in their "habitual" state often show variations from the normal. These latter variations are in most cases inconstant, and some of them are functional in their nature. 5. Apart from the rare occurrence of marked congenital abnormalities, pupillary symptoms in imbecili and idiocy are usually unimportant. A slight degree of irregularity is occasionally present. The light - reflex is rarely impaired; the sensory and psychical reflexes may be diminished, occasionally absent. 6. In hebephrenia, diminution or loss of "unrest" and of the psychical and sensory reactions may be observed; there may be changes in the form and position of the pupils. 7. In katatonia, there is frequently diminution or loss of the sensory and psychical reactions and of unrest; temporary or changing irregularity, eccentricity, and inequality of the pupils are often present. Variation in the activity of the light- reaction may occur, usually a diminution. 8. The sensory reaction may be diminished in paranoia especially where there is a certain degree of dementia. 9. In melancholia of involution a slight degree of inequality and irregularity of the pupils is often perceptible. Changes in the form, position and size - relation of the pupils may occur. In a few cases the light- reflex is sluggish, and the sensory reaction may be inactive, rarely absent. 10. The pupils in senile dementia tend to be small, usually reacting somewhat sluggishly to light; the near vision reaction may also be impaired. The sensory reflex is occasionally absent; it may be impaired wher the light and near -vision reflexes are active. ll. The melancholic phase of manic- depressive insanity presents but few pupillary symptoms. Slight irregula ity is not uncommon; anisocoria is relatively infrequ If there is change in the form or size -relation of the pupils, it is slight in amount. sluggish in a few cases only. In the maniacal phase, slight irregularity and inequality of the pupils are frequently observed. In a certain number of cases the sensory reflex is sluggish. Change in these symptoms may accompany change in the mental state. The average pupil -diameter is the same in the melancholic as in the maniacal phase. The pupil -diameter is .smaller on the whole in patients who are habitually in a state of excitement. Here there are no marked pupillary disturbances. In a small proportion of cases the sensory reflex is sluggish. 12. In terminal dementia, irregularity of the pupil is not very common. Slight anisocoria is rather more frequent. As age advances, the influence of senility on the condition of the pupils gradually makes itself felt. 13. Apart from general paralysis, epilepsy, and gros brain- lesions, the more evident pupillary symptoms are found in the toxic psychosbs and in senile dementia. In katatonia and the habitual condition of insane epileptics, transient sluggishness of the light reaction may be observed. In many kinds of insanity there is a tendency towards variation in the form, position, and size - relation of the pupils. 14. Diminution and loss of the sensory and psychical reactions and of pupil- unrest are typically frequent, been i hasAclaimed, in the triad of diseases included in the term: dementia praecox. These symptoms however, are not uncommon in other types of insanity; and no special diagnostic importance can be attached to their occurrence. 15. Further investigation of the condition of the pupils in insane patients is required. Each case should be re- examined at regular intervals, and control -observations of a sufficiently large number of healthy persons should be carried out under similar conditions.