It is desirable in the first place to clear away some general misconceptions on the subject. The task of assimilating our new experiences in connection with the war with any previously held theory of neurotic affections has undoubtedly been rendered more difficult by the attitude of those workers whose interest in such problems is of contemporary origin. They lay much too much emphasis on the newer and perhaps more sensational aspects of the phenomena observed, instead of trying to correlate the more familiar and better understood ones. This attitude has been so pronounced with some writers that one might almost imagine that before the war there had never been such calamities as wrecks, earthquakes, and railway accidents, and that men had never been tried to the limit of their endurance with privation, fatigue, and danger, while familiar symptoms like hysterical blindness and paralysis are thought worthy of detailed description and are treated almost as novelties in psychological medicine. So far as I know, however, although some symptoms—e.g., dread of shells—assume a form that is coloured by war experiences, no symptom, and hardly any grouping of symptoms, occurs in war neuroses that is not to be met with in the neuroses of peace, a fact which in itself would suggest that fundamentally very similar agents must be at work to produce the neurosis in both cases. Another very prevalent misconception, one strengthened by the official use of that unfortunate catch-word “shell-shock”, is that war neuroses constitute a more or less unitary syndrome. It is so often forgotten that the term “shell-shock” can only mean, and no doubt was originally intended to mean, a certain ætiological factor, and not the disease itself. I have preferred to use the less ambiguous and more obviously ætiological term “war-shock,” one coined, I think, by Eder[9]. Even when the term “shell-shock” is avoided, its place is usually taken by the all-embracing expression “neurasthenia”—in most cases, in fact, where there are no physical symptoms of hysteria present. True neurasthenia in its strict sense, on the contrary, is a relatively rare complaint, certainly in anything like a pure form; I have not come across a single case myself in connection with the war. The results of war strain are anything but unitary; most of the diverse forms of neurosis and psychoneurosis are found to be represented, and until these are adequately distinguished one from another it is impossible to make any satisfactory study of their individual pathology. A further point still more often overlooked, and perhaps even more important, is that not only are the results diverse, but the ætiological factors concerned in war strain are much more complex than is sometimes realised. Careful study of the cases shews that what was the most important pathogenetic agent with one patient had nothing to do with the neurosis of a second patient, although he may have been equally exposed to its influence.