82 THE GROWTH OF THE BRAIN. 



All the curves which have been here presented are 

 sinuous, thus indicating that periods of more rapid 

 growth alternate with those in which it is slower. As 

 has been pointed out, such a rhythm can be followed in 

 the segmenting ovum. When the cells become more 

 numerous the period of these alternations becomes 

 longer. There is apparently an acceleration of growth 

 processes at the sixth month of foetal life, at birth, at 

 the seventh year, and at adolescence, this being the last. 

 During the growth period of the healthy child it becomes 



PERCENT 



VRSi Z 3 4 S G 78 9 iO II IZ 13 l+ IS 16 17 18 19 20 V ZZ tt Z4ZS 



FIG. 15. Curve to show the rate of increase in stature 

 during the first twenty-five years of life. M. Males. 

 F. Females. The percentages of increase are 

 measured along the vertical axis, the ages along 

 the horizontal one. (Based on Roberts, Table 8.) 



of interest to inquire how the circling seasons and re- 

 volving day may influence the process. The observa- 

 tions of Malling-Hansen 1 on Danish children from nine 

 to fifteen years of age show that by far the most rapid 

 increase in stature was in the third of the year between 

 the middle of April and the middle of August, while 

 the third of the year between the middle of August and 

 the middle of December was the one in which they 

 gained nine-elevenths of their annual increase in weight. 

 These observations have been made, however, upon 



1 R. Malling-Hansen, Pcriodcn im Gewicht der Kinder und in 

 der Sonnenwarme, Copenhagen, 1886. 



