The advisability of studying dementia precox in relation to other nervous disorders is emphasized. When so considered dementia precox by virtue of its hereditary nature and progressive course is found to resemble most closely the hereditary degenerations or abiotrophies. If collected into a group and these conditions and others which closely resemble them although not definitely shown to be of the same nature, are found to comprise perhaps fifty distinct nervous disorders, which attack many different nervous functions producing a variety of motor sensory and mental disturbances. The pathology of dementia precox is best explained by considering it to be one of this group—one in which the affected structures happen to be particularly important in mental activity. The logical field for further investigation appears to be that of heredity.