And what should one say to this honest physician? Should one tell him to go and be a physician to the poor? Would he be any happier there? He could tell the poor the causes of their diseases, and they would listen patiently--they are trained to listen, and to accept what they are told. Here is a girl living in an inside bedroom in a tenement, and working ten or eleven hours a day in an unventilated factory, and she is ill with tuberculosis. The physician tells her that she needs plenty of fresh air and rest, and a lot of eggs and milk in her diet. He tells her that, and he knows that she has as much chance of carrying out his orders as of flying to the moon. Or maybe he comes upon a typhoid epidemic, and discovers, as happened to a friend of mine in Chicago, that there is defective plumbing in some houses owned by the political leader of the district. Or maybe it is a case of venereal disease, in a young man who was drafted into the army and turned loose amid the joys of Paris. Maybe it is just a commonplace, every-day story of a room full of school children, 22 per cent of them undernourished, as is the case in New York City, and the parents out of work a part of the time, and with no possibility in their lives of ever earning enough to feed the children properly. When you confront these universal facts of our present social order, you realize that the problem of disease is not merely a problem of the body, but is a problem of the mind as well; a problem of politics and religion and philosophy, of the whole way of thinking of the so-called civilized world. A book of health which did not point out these facts would be, not a book of health, but a book of sham. But meantime, while we are trying to change the world's ideas, we have to live, and we can do our work better if we keep as well as possible. I have tried to point out the way; it is, as you can see, a matter in part of the body and in part of the mind. All the bodily regime here laid out has its basis in mental habits; all wise and wholesome ways of life can, at the age when our minds are plastic, be made into "second nature"--things which we do automatically, without effort or temptation to do otherwise. This is the real secret of true happiness in the conduct of our personal lives; to acquire self-control, to rule our desires and our passions, not harshly and spasmodically, but serenely, as one drives a car which he thoroughly understands. It is in vain that we preach freedom to men who have not this self-mastery; as the poet tell us: "The sensual and the dark rebel in vain, slaves of their own compulsion." And of all the personal possessions which man can attain on this earth, the most precious is the one of a sound mind controlling a sound body. I close this book by quoting some verses written by Sir Henry Wotton three hundred years ago, which I have all my life considered one of the noblest pieces of poetry in our heritage: THE CHARACTER OF A HAPPY LIFE