Not that there is anything mysterious with regard to the immediate causes of this obvious decline in the health and robustness of the race. Miss Nightingale tells us that more than half of all the sickness in the world comes of breathing bad air. She speaks feelingly of the time, not long passed, when the winds of heaven played freely through every house, from Windsor Castle to the laborer's cottage, and when every lady put forth muscular effort in the polishing of surfaces. That was the time when bread was an article of diet, and the Devil had not invented hot biscuit. The agreeable means of self-destruction, now so cheap and universal, were unknown, or very costly; and the great mass of the people subsisted, necessarily, upon the plain fare which affords abundant nourishment, without overtasking the digestive powers. Terrible epidemics, against which the medical science of the time vainly contended, swept off weakly persons, shortened the average duration of life, and raised the standard of health. But now we can all pervert and poison ourselves if we will, and yet not incur much danger of prompt extinction. Indeed, it is hard for the most careful and resolute person to avoid being a party to the universal violation of natural law. Children, of course, are quite helpless. How could I help, at eight years of age, being confined six hours a day in a school, where the word "ventilation" was only known as an object of spelling? How could I help, on Sunday, being entombed in a Sunday-school room, eight or nine feet high, crowded with children, all breathing their utmost? I hated it. I loathed it. I protested against it. I played truant from it. But I was thirteen years old before I could escape that detested basement, where I was poisoned with pernicious air, and where well-intentioned Ignorance made virtue disgusting, contemptible, and ridiculous, by turns. As all our virtues support one another, so all the vices of modern life are allies. Smoking and drinking are effects, as well as causes. We waste our vital force; we make larger demands upon ourselves than the nature of the human constitution warrants, and then we crave the momentary, delusive, pernicious aid which tobacco and alcohol afford. I suppose the use of these things will increase or decrease, as man degenerates or improves. This subject, I repeat, is the next great matter upon which we have to throw ourselves. The republication of these essays is only to be justified on the ground that every little helps.