926 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



vidual to the type throughout the period of growth. The course of growth 

 of British boys and girls from birth up to the age of twenty-four is graphically 

 shown in the accompanying diagram (Fig. 316). Growth is here seen to be 

 rapid during the first five years of life, then slower up to the tenth or 

 the twelfth year. From thence up to the fifteenth or the seventeenth year 



that is, preceding and including puberty marked acceleration occurs, 



which in turn is followed by slow increase up to the twentieth or the 

 twenty-fifth year. For from five to ten years thereafter slight increase in 

 height occurs, while from the accumulation of fat the weight usually rises 

 markedly up to the fiftieth or the sixtieth year. One of the most interesting 

 results revealed by statistics is the relative growth of the two sexes. From 

 birth up to about the age of ten or twelve, boys show a slight and increasing 

 preponderance over girls, but the two curves are nearly parallel. The prepu- 

 bertal acceleration of growth in girls, however, precedes that of boys, and is 

 even accompanied by some check in the male growth, with the result that 

 between the ages of twelve and fifteen girls are actually heavier and taller 

 than boys. This fact, first pointed out in 1872 by Bowditch l from observa- 

 tions on several thousand Boston school children, has been abundantly con- 

 firmed by Pagliani in Italy, Key in Sweden, Schmidt in Germany, Porter in 

 St. Louis, and others. At about fifteen years boys again take the lead and 

 maintain it throughout life. Boys grow most rapidly at sixteen, girls at thir- 

 teen or fourteen, years of age ; the former attain their adult stature approxi- 

 mately at twenty-three to twenty-five, the latter at twenty to twenty-one years. 

 The details of growth and the actual measurements vary considerably with 

 race ; thus the supremacy of the American girl over her brother appears to be 

 less marked and to cover a shorter period than that of the English, German, 

 Swedish, or Italian girl. Children of well-to-do families are superior to 

 others in both weight and stature. Disease may alter the form of the curve 

 of growth. But the final result seems to depend less upon external condi- 

 tions than upon race and sex. As an interesting accessory fact it was found 

 by Porter 2 that well-developed children take a higher rank in school than less- 

 developed children of the same age. If the percentage annual increase of 

 the total weight be computed, it is found to diminish throughout life, very 

 rapidly during the first two or three years, later more slowly and with minor 

 variations of increase and decrease ; that is, as growth proceeds and the powers 

 of the individual mature, the power to grow becomes rapidly less. This is a 

 peculiar and most interesting fact and has not been explained. It would seem 

 to signify that the sum of the vital powers declines from birth onward. Many 

 facts indicate that the common conception, dating from the time of Aristotle, 

 of human life as consisting of the three periods of rise, maturity, and decline, 

 must give way to a more rational idea of a steady decline from birth. 



1 H. P. Bowditch : Eighth Annual Report of the State Board of Health of Massachusetts, 1877. 



2 W. T. Porter : " The Physical Basis of Precocity and Dullness," Transactions of the Acad- 

 emy of Science of St. Louis, vi., No. 7, 1893. See also " The Growth of St. Louis Children," 

 Transactions of the Academy of Science of St. Louis, vi., No. 12, 1894. 



