Half a century ago Maudsley wrote “A pregnant but very difficult question of which little or no thought has ever been taken by writers on insanity is—What is the cause of the particular form which the disorder takes in a given case? Why does it assume one complexion rather than another? At the outset it is certain that what appears to be the same cause shall occasion different forms of insanity in different persons and even in the same person at different periods of life, and that the same form of disorder shall be produced by different causes; this being so it is plain that the special determining conditions lie hidden in that unknown region which we call by such names as ‘temperament’ and ‘idiosyncrasy.’”

For several years past my attention has been directed to a series of cases in which the principal symptom has been the presence of hallucinations.

Until the outbreak of hostilities in August, 1914, the number of cases of mental disorder associated with head injury investigated by any one individual must of necessity have been very small. Hence the sparcity of literature on this subject. Never before the outbreak of the late war have so many men been engaged in armed conflict against one another, and never before have arms of such a destructive kind been employed.

Upon the outbreak of the recent war, most of us, after experiencing a transitory phase of almost breathless suspense, passed, I think, into a state of apprehensive ignorance.

In presenting this paper I must erare indulgence. I feel rather in the position of an inexperienced player who, from a spirit of good nature, has been induced to “make up a ‘four’ at bridge.” He will be lucky if he does not find at the end of the game that his good nature is taken less into account than his presumption.