THE CYCLE OF LIFE 403 



rate of growth, in fact, varies inversely with the degree of 

 differentiation '. 



In Man there are three maxima of rate of growth. The 

 first is before birth, but its precise occurrence is uncertain. 

 As we have abeady mentioned, the increment from the 

 third to the fourth month is 600 per cent. It then falls 

 with great rapidity between the fourth and sixth months, 

 and thereafter more slowly tiU birth. The second maxi- 

 mum is in the first year of infancy, when the increase of 

 weight is (according to Minot) about 200 per cent., and 

 the length (according to Schwerz) increases from 50 centi- 

 metres to about 75 centimetres. In the following five 

 or six years the rate of growth becomes slower and slower. 

 The third maximum is towards the time of puberty, at 

 about the age of twelve to thirteen for girls, of fourteen to 

 sixteen for boys. In the early years the length of the 

 body increases more rapidly than the weight ; later on, 

 after puberty, increase in weight takes the lead. 



An interesting point in regard to growth is, that it 

 may differ markedly in the two sexes. The male is 

 often a pigmy compared with the female, though the egg- 

 ceUs from which they developed may have been identical 

 in size. The growth of women is quite difierent from 

 the growth of men, and as this has been observed in aU 

 sorts and conditions, in many countries and races, it cannot 

 be referred to differences in habits. It is a constitutional 

 difference. It is not merely that the growth of women is 

 7 per cent, less than that of men ; the growth is on a different 

 scheme, with the parts in different proportions. 



When we say that growth is a regulated increase in the 

 amount of hving matter, we mean that it is not a steady 

 continuous increase in proportion to the available nutritive 



