A due supply of appropriate food and of pure air, sufficient protection and cleansing of the surface, moderate labor and refreshing rest, are the necessary conditions of health, and cannot be disregarded, in the least degree, without a loss of force. The privation of even a single meal, or the use of food that is hard of digestion or innutritious, and the loss of any of the needful sleep, are followed by a corresponding loss of effective power, as surely as the slackened fire in the furnace is followed by lessened steam and power in the engine. Whosoever, then, wishes to sustain his own forces or those of his laborers with the least cost, and use them with the greatest effect, must take Nature on her own terms. It is vain to try to evade or alter her conditions. The Kingdom of Heaven is not divided against itself. It makes no compromises, not even for the necessities of nations. It will not consent that any one, even the least, of its laws shall be set aside, to advance any other, however important. Each single law stands by itself, and exacts complete obedience to its own requirements: it gives its own rewards and inflicts its own punishments. The stomach will not digest tough and hard or old salted meats, or heavy bread, without demanding and receiving a great and perhaps an almost exhausting proportion of the nervous energies. The nutritive organs will not create vigorous muscles and effective limbs, unless the blood is constantly and appropriately recruited. The lungs will not decarbonize and purify the blood with foul air, that has been breathed over and over and lost its oxygen. However noble or holy the purpose for which human power is to be used, it will not be created, except according to the established conditions. The strength of the warrior in battle cannot be sustained, except in the appointed way, even though the fate of all humanity depend on his exertions.