752 THE AMERICAN JOURNAL OF SOCIOLOGY
his mate in the school keeps forging ahead, this little unfortunate soon comes to a dead stop, because untoward conditions force him to solve the practical problems of existence too early, and he lives out his days in the circle of ideas and feelings and voli- tions which are appropriate to his more or less primitive environ- ment. If every child born in America during the next quarter of a century should receive such a training as do the street arabs on Clark street, in Chicago, our civilization would revert to the stage of semi-barbarism through which it passed ages ago.
The principle I wish to impress is that the stability and constant advancement of the race require a continual length- ening of the plastic age, so that each new generation may master all that has been accomplished by those who have gone before. We have pushed beyond the Indian in the development of cul- ture because, for one reason, our youth remain in the acquisitive condition for a longer period, and our social regulations happily are such that we gladly protect them in their immaturity. In this way all that comes into the possession of the race at any age is acquired by the age following. And as our people have become more intelligent, as knowledge and skill have accumu- lated, that is to say, as our race has evolved, the period of plas- ticity in our youth has been lengthening at a corresponding rate. Just as soon as the extending of this period of acquisition ceases, just then will the development of our people be arrested ; the one thing conditions the other. You cannot have a race pushing ahead uninterruptedly, while the new generations assume the functions of maturity as early as the preceding ones.
A study of the evolution of races will show, I think, that those only are leading in the march of civilization which do not require their youths to enter into the bread-and-butter relation with their environments until they have mastered all that has been achieved in the different fields in which they are to labor. This must be the guiding principle in every progressive com- munity one generation must care for the next until the new one has made itself master of all the intellectual and moral and motor attainments that the older one possesses. Each genera-
