The field of play is as wide as life and its varieties far outnumber those of industries and occupations in the census. Plays and games differ in seasons, sex, and age. McGhee[19] has shown on the basis of some 8,000 children, that running plays are pretty constant for boys from six to seventeen, but that girls are always far behind boys and run steadily less from eight to eighteen. In games of choice, boys showed a slight rise at sixteen and seventeen, and girls a rapid increase at eleven and a still more rapid one after sixteen. In games of imitation girls excel and show a marked, as boys do a slight, pubescent fall. In those games involving rivalry boys at first greatly excel girls, but are overtaken by the latter in the eighteenth year, both showing marked pubescent increment. Girls have the largest number of plays and specialise on a few less than boys, and most of these plays are of the unorganized kinds. Johnson[20] selected from a far larger number 440 plays and games and arranged the best of them in a course by school grades, from the first to the eighth, inclusive, and also according to their educational value as teaching observation, reading and spelling, language, arithmetic, geography, history, and biography, physical training, and specifically as training legs, hand, arm, back, waist, abdominal muscles, chest, etc. Most of our best games are very old and, Johnson thinks, have deteriorated. But children are imitative and not inventive in their games, and easily learn new ones. Since the Berlin Play Congress in 1894 the sentiment has grown that these are of national importance and are preferable to gymnastics both for soul and body. Hence we have play-schools, teachers, yards, and courses, both for their own value and also to turn on the play impulse to aid in the drudgery of school work. Several have thought that a well-rounded, liberal education could be given by plays and games alone on the principle that there is no profit where there is no pleasure or true euphoria.