Page:Popular Science Monthly Volume 38.djvu/118

108 The growth continues after the last period, but more slowly. The development of girls also presents distinct periods, but the changes occur a few years earlier than in boys. It may be mentioned for comparison that American boys are taller and heavier than Swedish boys during the period of puberty, but that otherwise the Swedes excel all other boys and pass the Americans in their nineteenth year. Danish boys compare well with Swedish, and Hamburg boys, according to Kotelmann's researches, come very near to them. The smallest boys examined were those in Belgium and northern Italy. Swedish girls are decidedly taller and have greater weight than the girls examined in other countries. Comparing the subjects by stations in life, the more rapid growth begins a year earlier in the children of the well-to-do classes than in those of the poorer classes. Scanty and hard conditions of life are restrictive and hindering to the growth of children. The slow growth of the poorer children previous to the period of puberty is prolonged at the cost of the latter; it is as if something hindered these children from entering their period of more rapid development in the same year of their life as children living in better circumstances. The development of puberty is delayed in them, but as soon as it is begun it goes on with increased rapidity, and, in spite of the delay, is completed in the same year as it is in the better situated children. We see here a striking example of the elasticity that resides in children and asserts itself in the processes of growth. A feather can be bent very forcibly or nearly doubled up, without losing the power of springing back to its former condition. But if the pressure is too strong or lasts too long, the power is lost—the quill gives way or acquires a permanent set. So a child which has been held back in its growth by unfavorable circumstances has a marvelous power of winning back what it has lost, and of returning in growth to its development-curve. But if the disturbing influences take too sharp a hold or persist too long, the child continues so far backward in its development that it is never able to make it normal again.

It is an interesting question, and especially important in relation to education, whether the growth of children goes on evenly during the different seasons, in summer and winter. Some penetrating researches in this matter have been made by Pastor Malling-Hansen, superintendent of an institute for the deaf and dumb in Copenhagen. According to them, children exhibit a relatively light growth from the end of November to the end of March. This period, which includes all the winter months, is followed by a second, from the end of March till July or August, during which the children grow rapidly in height, but their increase in weight is reduced to a minimum. After this follows a