78 THE POPULAR SCIENCE MONTHLY. 



eacTi of the three years the greatest increase in weight took place 

 in the fall until the beginning of winter, then till the end of April 

 the increase grew less, and after this time a loss in weight was no- 

 ticed. At times the increase in weight of the children would cease 

 suddenly for a few days, and occasionally during the time when 

 an increase was expected a general decrease occurred. Based upon 

 his measurements and annotations, Malling-Hansen framed the 

 following rule : The weight of a boy ranging from the age of nine 

 to fifteen undergoes three periods annually — a maximum, a me- 

 dium, and a minimum period. The maximum period lasts four 

 and a half months, commencing in August and ending the middle 

 of December ; the medium stage has the same duration, from the 

 middle of December to the end of April. The minimum period 

 appears during the remaining three months, from the end of April 

 to the end of July. The increase in weight during the maximum 

 period is three times that of the medium period, and almost all 

 the gain of the medium period is again lost during the minimum 

 period. From the working of this law it follows that in changing 

 the diet at academies, schools, and asylums, the season should be 

 considered. A good diet would give less satisfactory results if 

 observed from April to June, than a poorer diet if noted from 

 August until December. 



In the same manner as the increase in iveight, the increase of 

 groivth fluctuates, and can likewise be divided into three periods. 

 These periods commence and close about a fortnight before the 

 periods of weight, but in such a manner that the minimum period 

 of growth occurs at the time when the weight remains stationary, 

 and may at times even be coincident with important loss in 

 weight. Growth takes place, one might say, at the expense of 

 the increase of weight. Accurate observation showed that the 

 general growth of the trees in the garden of the institution corre- 

 sponded essentially with the growth of the children. The maxi- 

 mum period of growth upward is followed by that of increase in 

 circumference. The growth of the human body and the growth 

 of the trees are consequently influenced in the same manner by 

 some disposing cause. But what is this cause ? 



As the fluctuations referred to above coincided strikingly with 

 the fluctuations of atmospheric warmth, Malling-Hansen believed 

 that they could be attributed to local meteorological conditions ; 

 and it was really shown that with a rise of temperature the 

 weight increased, and vice versa. It was, however, ascertained 

 that during the minimum period a rapid rise of temperature but 

 slightly affected the increase in weight, and in the same way the 

 decrease in temperature during the ma.ximum period influenced 

 the weight but little. 



Furthermore, it seemed remarkable that the children should 



