108 THE POPULAR SCIENCE MONTHLY. 



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 men- 

 tioned for comparison that American boys are taller and heavier 

 than Swedish boys during the period of puberty, but that other- 

 wise 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 coun- 

 tries. 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 con- 

 ditions of life are restrictive and hindering to the growth of chil- 

 dren. 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 in- 

 creased 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 influ- 

 ences 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 rela- 

 tion to education, whether the growth of children goes on evenly 

 during the different seasons, in summer and winter. Some pene- 

 trating 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 in- 

 crease in weight is reduced to a minimum. After this follows a 



