I had now been in the trenches for five months and was getting past my prime. For the first three weeks an officer was not much good in the trenches; he did not know his way about, had not learned the rules of health and safety, and was not yet accustomed to recognizing degrees of danger. Between three weeks and four months he was at his best, unless he happened to have any particular bad shock or sequence of shocks. Then he began gradually to decline in usefulness as neurasthenia developed in him. At six months he was still more or less all right; but by nine or ten months, unless he had a few weeks’ rest on a technical course or in hospital, he began to be a drag on the other members of the company. After a year or fifteen months he was often worse than useless. Officers had a less laborious but a more nervous time than the men. There were proportionately twice as many neurasthenic cases among officers as among men, though the average life of a man before getting killed or wounded was twice as long as an officer’s. Officers between the ages of twenty-three and thirty-three had a longer useful life than those older or younger. I was too young. Men over forty, though they did not suffer from the want of sleep so much as those under twenty, had less resistance to the sudden alarms and shocks. Dr. W. H. R. Rivers told me later that the action of one of the ductless glands—I think the thyroid—accounted for this decline in military usefulness. It pumped its chemical into the blood as a sedative for tortured nerves; this process went on until the condition of the blood was permanently affected and a man went about his tasks in a stupid and doped way, cheated into further endurance. It has taken some ten years for my blood to run at all clean. The unfortunates were the officers who had two years or more continuous trench service. In many cases they became dipsomaniacs. I knew three or four officers who had worked up to the point of two bottles of whisky a day before they were lucky enough to get wounded or sent home in some other way. A two-bottle company commander of one of our line battalions still happens to be alive who, in three shows running, got his company needlessly destroyed because he was no longer capable of taking clear decisions.