In the army, it is proverbial that the time of fatigue and danger is not the time of disease; it is during the inactive and listless months of a campaign that crowds of patients pass to the hospitals. In both these cases it is the active exercise of the mind giving strength to the brain, and through it, healthy vigour to the body, which produces the effect. Shakspeare has not been unobservant of the consequences of excitement of mind on the bodily functions. In King Henry IV., when Northumberland is told of the fatal tidings from Shrewsbury, and is informed of the death of his son Percy, he breaks out,— “For this I shall have time enough to mourn. In poison there is physic; and these news That would, had I been well, have made me sick, _Being sick, have in some measure made me well_: And as a wretch whose fever-weakened joints, Like strengthless hinges, buckle under life, Impatient of his fit, breaks like a fire Out of his keeper’s arms; _even so my limbs_, Weakened with grief, being now enraged with grief, Are thrice themselves.” In illustration of the same principle, we have only to refer our readers to the ever-memorable Walcheren expedition. It has been stated that while our troops and seamen were actively engaged in the siege and bombardment of Flushing, exposed to intense heat, heavy rains, and poisonous exhalations from the malarious soil, inundated by the turbid waters of the Scheldt, scarcely a man was on the sick list; the excitement of warfare, the prospects of victory, and the expectation of booty, completely fortifying the body against all the potent causes of disease that environed the camp and the fleet. In the celebrated retreat of the “Ten thousand Greeks” under Xenophon, the troops were subjected to great mental despondency. They had to cross rapid rivers, penetrate gloomy forests, drag their weary way over vast and burning deserts, scale the summits of rugged mountains, and wade through deep snows and pestilent morasses, in continual fear of death or capture. It was a sense of the despondency which misfortune was producing among the troops that induced Xenophon, in his address to his companions on the fearful night which preceded the murder of Clearchus, to say, “The soldiers have at present nothing before their eyes but misfortune. If any one can persuade them to turn _their thoughts into action_ it would greatly encourage them.” It was to effect this purpose that the consummate general ordered everything in the camp, except the sword, to be abandoned. He inspired the hopes of his soldiers, roused their minds into activity, and thus prevented the development of serious disease among the troops.