GROWTH OF THE HUMAN BODY 



709 



years) than the greatest growth in weight (sixteenth and seventeenth years). 

 Since increase in weight is of greater significance than increase in height, 

 the sixteenth and seventeenth years may be regarded as the years of most 

 rapid physical development (cf. page 144). 



After the seventeenth year the yearly rate of growth in height and weight 

 is less, but the increase continues until about the twenty-first year, when the 



FIG. 304. Curves representing the height and weight of boys and girls of different age, after Key. 



youth reaches his full physical stature. The height at this time is on the aver- 

 age 172 cm. and the body weight 65.2 kg. The man continues to grow, 

 though very slowly, for several years more. 



The physical development of girls runs quite a different course. The 

 period of feeble growth, which is so sharply marked for boys just previous 

 to puberty, comes earlier for girls, namely, so far as concerns height, in the 

 ninth year. The yearly increase in height of girls from the ninth to the seven- 

 teenth year is 7, 4, 5, 5, 6, 5, 4, 2, 1 cm. The increase in weight for the 

 same years is 3.4, 1.9, 2.5, 2.5, 4.0, 3.7, 5.2, 4.1, 2.7, 3.0 kg. respectively. 

 We see that there is a period in the development of girls also, from the ninth 

 to the eleventh years inclusive, when the rate of growth in weight is relatively 

 slow. The true puberty period, which is characterized by a rapid growth in 

 weight, begins in the twelfth year and lasts until the fifteenth year (inclusive;. 



With girls the growth in height continues until only about the seventeenth 

 year, while the increase in weight can be demonstrated up to the twentieth 

 year. 



