He shows that the death-rate of the soldier in England is less than one per cent., and also considers the stated mortality of three per cent. for the continent of Europe as much too high. The mortality on the continent is greater than in England, and greater in England than in Scotland. In times of peace, the mortality of soldiers is not much greater than that of the civil laborers; but during campaigns no limit can properly be given, for the vicissitudes are so rapid, and the exposures so varied, that the chances of life and death cannot be estimated with fairness, or with any degree of certainty. But when encampments are arranged, and occupied for any considerable length of time, the possibilities and probabilities of health may then be considered with propriety. III. These chances and these causes of general mortality depend upon the atmospheric influences, the mephitism of the soil, the density of the population, and the excellence of the food and shelter, as well as upon the natural vigor and strength of the individual. Some classes of human beings have greater tenacity of life than others, but all are affected by vicious influences, and yield sooner or later to the elements of destruction. "Everything in the animal economy is regulated by fixed and positive laws." "We live on our forces," says Galen: "as long as our forces are sound, we can resist everything; when they become weak, a trifle injures us." The truth of this remark is well illustrated in the life of the soldier, whose health is in exact ratio to the condition in which he is placed. And his mode of existence, the combined influence of food, exposure, and the training of mind and body, give a peculiar character, which requires, when disabled, special modification of treatment, and a particular kind of experience. The ancient physiologists distinguished two kinds, or rather two provisions of strength--the forces in reserve and the forces in use; or, as they said, "Vires in posse et vires in actu;" or, as Barthez describes it, the radical forces and the acting forces. The young soldier, supported by this buoyancy of the unknown force of life, recovers from terrible shocks and disasters to his system, while the old man, fatigued and exhausted by the great and protracted labors of active campaigns, feels that he has the hidden resources--the reserved and superabundant powers of youth--no longer. IV. "The atmospheric influences, the mephitism of the soil, and the inhabited locality, are the three principal conditions of the causes of general mortality," says Pringle. He should have added food; for diet, of all external causes, affects the condition of the human race more than any other. Those who have observed the mortality curve follow the harvests in Ireland and Germany, and noticed how strangely the number of the dead corresponded to the scantiness of food, and those who have experimented with the feeding of domesticated animals, will agree with me on this point.