Personal and social hygiene in matters of sex are, in very important ways, dependent upon moral and religious training. On the other hand, morals and religion are in important ways dependent upon forces set free by the growth and activity of sex instincts and powers. One of the most significant facts in modern social progress is its recognition of this interdependence of mind and body. We have learned that physical health depends upon peace of mind, hopefulness, courage, and many other things that have seemed in the past to be purely mental or spiritual; and we have learned also that the character of people and the spirit in which they do their work depend upon their health, upon conditions of food and warmth and shelter, things which in the past have been regarded as affecting only the physical man. It is now somewhat out of date to set physical conditions over against moral and religious; every great human problem is more and more clearly seen in this day to involve all these conditions in its rise, and to require thoughtful consideration of them all for its solution. As we face the problems of sex, we must recognize the importance of fresh air, exercise, wholesome food, clean cups and clean towels, and we must also recognize the importance of clean thoughts and high purposes. We must know clearly the facts of biological and medical science, and with them in mind we must touch the springs of conduct in affection and imagination. Our aim must be to achieve that mastery over the forces of life finely expressed by Browning's Rabbi ben Ezra: "Nor soul helps flesh more, now, than flesh helps soul." We may consider, first, how, in matters of sex, flesh helps soul; second, how soul helps flesh; and third, how in normal childhood and youth soul and flesh grow together in mutual help. The first great outstanding fact is that the physical powers of sex reach maturity in the same years in which the moral and religious instincts are greatly quickened. If we recall our youth, we must realize that, in the years between twelve and twenty, our lives were greatly disturbed and perplexed, and also greatly exalted and inspired by desires and impulses partly toward the opposite sex and partly toward the service of God and our fellows. In the normal adolescent boy or girl there is a powerful expanding and enriching of sex thoughts and desires and purposes. There is also a rapid development of social sympathy and passion; the revolutionary movements of all lands are recruited from those who like Shelley have in their youth vowed,-- "I will be wise, And just, and free, and mild, if in me lies Such power, for I grow weary to behold The selfish and the strong still tyrannize Without reproach or check." And there is a wonderful flowering of the young life in religious feeling and aspiration; a large majority of religious conversions take place in adolescence.