perature. Nothing else will permanently appease them. Millions of prisoners, school-children and factory-slaves, pine for lung-food as a starving man yearns for bread, and that hunger cannot be stilled with cough-pills, but only with fresh air.
Pure cold air is also a sovereign remedy for digestive disorders. The assimilative capacity of the human organism increases with the distance from the equator. An Esquimaux can digest a quantum of food that would crapulate three Hottentots and six Hindus. Camping in the open air whets the appetite even without the aid of active exercise. A bracing temperature exacts a sort of automatic exercise: It accelerates the circulation, it promotes the oxidation of the blood, and stimulates the whole respiratory process. The generation of animal caloric has to be increased to balance the depression of the external temperature. Hence the invigorating effect of mountain air and of sea-voyages. The first dose of the tonic can be applied in-doors by gymnastics in the ancient sense of the word that implies exercise in a state of nudity ("gymnos," in Greek, meaning simply "naked")—a few minutes' pause between undress and bedtime.
People who have got rid of the night-air su-
