ONTOGENKI K « i i;\ l. 01 m II.!>. 



13 



the lad is quickly transformed into a broad-shouldered, broad-chested, 



stocky man (plate 3, fig. 3, plate :>, I'm. 8) and accordingly the 

 of build rises much more in the young man than in the young woman 

 (plate 7, figs. 4 and 5). Consequently the adult female build, as 

 measured by relative chest circumference, is relatively Bmall. At 

 about 19 or 20 years' growth in stature has usually practically ceased. 

 Meanwhile chest-girth increases slowly by the enlargement of trunk 

 muscles and deposition of fat. Weight i-, indeed, stated to increase, 

 on the average, until the age of 55 years (tables G and 7). 



Relative 

 chest 



girth. 



670 



660 



650 



640 



630 



620 



V v7\ 



v \ f\ 1 



\/ r 



I 







610 



I- M 



itha 



Fro. 2. — Polygon of relative chest-girth in infants, from liinli t.> fourteen months, with 

 smoothed curve of build (dotted line). Data from New York Milk Stations and I >r 

 B. Ratner. 



It may be well to consider briefly, necessarily somewhat specula- 

 tively, the significance of this ontogenetic change in build. First of 

 all, the high relative chest circumference of infancy is due chiefly to 

 the extremely short legs of the infant. Leg-length constitutes only 

 about 40 per cent of stature at birth, whereas it comes t<> constitute 

 53 to 55 per cent at maturity. Consequently, the relative leg-length 

 at infancy is only a trifle more than 70 per cent of tic adult relative 



