The most positive results of this orienting study appear to be the unlikelihood of euphoria and allied symptoms in the "mild" or non-atrophic cases and the unlikelihood of certain symptoms, here termed contra-environmental, in the severe or atrophic cases. Perhaps these statistical facts may lay a foundation for a study of the pathogenesis of these symptoms. Meantime the pathogenesis of such symptoms as amnesia and dementia cannot be said to be nearer a structural resolution, as these symptoms appear to be approximately as common in the "mild" as in the "severe" groups. But in both papers dealing with paresis [2,4] we rest under the suspicion that the delusions are possibly of cerebral manufacture. Of course, a lesion somewhere outside the brain is not unlikely to be projected through the diseased brain, and SOMATIC delusions in the paretic are rather likely to represent something in the viscera. It was desirable to get back to normal-brain material, to learn how the INTRINSICALLY NORMAL brain[5] could perhaps produce delusions from a particular environment. Could a particularly "bad" environment actually PRODUCE delusions? By chance, at about this stage in our studies of delusions, some work on fifth-decade insanities[6] was completed. This work seemed to show that the most characteristic (non-coarsely-organic) cases of involutional origin were much given to delusions (each of 24 cases studied), somewhat more so than to the hypochondria and melancholia which we commonly ascribe to the involution period. But this result is equivocal as to the environmental (i. e. allopsychogenic) power to produce delusions, since one could not rid oneself of the suspicion that the delusions were due to the degenerating brain. To return to our former results with the normal-looking brain: Case after case of the quasi-environmental group proved to be more essentially personal than environmental, until at last it almost seemed that the environment could seldom be blamed for any important share in the process of false belief. In short, we seemed to show that environment is seldom responsible for the delusions of the insane.