64 



CELL-DIVISION AND GROWTH 



II. 2 



rate, but Quetelet's measurements for males, being the completest 

 series, are given in the accompanying figure (Fig. 37). The 

 figure shows that at the end of the first year after birth the per- 



100% 



JcLd&med. iru 



2 34 5 6 78 9 K> II IZ 13 14 15 16 17 18 19 ZO Z\ 22 



FIG. 37. Curve showing the yearly percentage increments in weight 

 of Boys. (From Minot, 1907.) 



centage increment is as high as 200 % (or nearly), but that then 

 this increment drops to just over 20 % at the end of the second year. 

 From this point the decline is slow but sure, until at the thirtieth 

 year the annual percentage increase is only 0-1 %. The change of 

 rate of growth in females is practically the same as in males. 



The monthly percentage increment immediately before birth is 

 about 20% according to Miihlmann's curve (Fig. 36); this repre- 

 sents an annual percentage increment of, say, 250%, and the annual 

 increase at the end of the first year is about 200 %. The post- 

 natal decrease of growth is, therefore, as in other mammals, a con- 

 tinuation of the prenatal change. Further, there are two points 

 at which the rate diminishes with great rapidity between the 

 fourth and sixth months of pregnancy and between the first and 

 second years after birth. It would be of the greatest interest 

 to discover the causes of these sudden decreases. Elsewhere the 



