This group includes recurrent cases of insanity or cases subject to relapses from an apparently normal mental condition to one of mental alienation. The patients differ from those of the previous group in that during their lucid intervals they pass as normal sane individuals. They are, however, liable to become so far out of accord with an environment which would have little or no influence on normal individuals, that attacks of temporary mental alienation develop at regular or irregular intervals. In other words, the mental equilibrium of these patients is so unstable that it becomes upset by the various influences which constitute the normal “stress” to which the several members of a civilised community are necessarily subject. Though the cases in this group grade insensibly into and, during their attacks, exhibit a mental symptomatology similar to that of those included in Group II, classes (a) and (b), the fact that they are sane during a greater or a lesser portion of their lives affords a sufficient reason for placing them in a separate group as one of the types of high-grade amentia.