Although the term shell-shock has been applied to a group of affections, many of which cannot strictly be designated as “shock,” and into the causation of which the effect of the explosion of shells is merely one of many exciting factors, this term has now come to possess a more or less definite significance in official documents and in current conversation. It is for this reason that we have chosen to use it rather than the more satisfactory, but less widely employed term, “War-Strain.” The reader will, therefore, understand that whenever the term shell-shock appears in these pages, it is to be understood as a popular but inadequate title for all those mental effects of war experience which are sufficient to incapacitate a man from the performance of his military duties. The term is vague; perhaps its use implies too much; but this is not altogether a disadvantage, for never in the history of mankind have the stresses and strains laid upon body and mind been so great or so numerous as in the present war. We may therefore expect to find many cases which present not a single disease, not even a mixture, but a chemical compound of diseases, so to speak. In civil life, we often meet with cases of nervous breakdown uncomplicated by any gross physical injury. We are scarcely likely, for example, to meet it complicated by gas poisoning and a bullet wound. Yet such combinations as these—or worse—are to be met with in the hospitals every day. This is perhaps an opportune place to point out a significant popular misunderstanding concerning the nature of such maladies as we shall discuss in this chapter. A common way of describing the condition of a man sent back with “shock” is to say that he has “lost his reason” or “lost his senses.” As a rule, this is a singularly inapt description of such a condition. Whatever may be the state of mind of the patient immediately after the mine explosion, the burial in the dug-out, the sight and sound of his lacerated comrades, or other appalling experiences which finally incapacitate him for service in the firing line, it is true to say that by the time of his arrival in a hospital in England his reason and his senses are usually not lost but functioning with painful efficiency.