The Wit and Humor of America, Volume I. (of X.) by Marshall Pinckney Wilder

Happiness and laughter are two of the most beautiful things in the world, for they are of the few that are purely unselfish. Laughter is not for yourself, but for others. When people are happy they present a cheerful spirit, which finds its reflection in every one they meet, for happiness is as contagious as a yawn. Of all the emotions, laughter is the most versatile, for it plays equally well the role of either parent or child to happiness.