CHAP. ITT.] THE PHASES OF LIFE. 409 



977. Shortly after the conclusion of the permanent den- 

 tition (the wisdom teeth excepted) the occurrence of puberty 

 marks the beginning of a new phase of life ; and the difference 

 between the sexes, hitherto merely potential, now becomes func- 

 tional. In both sexes the maturation of the generative organs is 

 accompanied by the well-known changes in the body at large ; but 

 the events are much more obvious in the typical female than in 

 the aberrant male. Though in the boy, the breaking of the voice 

 and the rapid growth of the beard which accompany the appear- 

 ance of active spermatozoa, are striking features, yet they are after 

 all superficial; and though, as we have seen ( 973), the curves of 

 his increasing weight and height undergo before and at this period, 

 characteristic variations, the general events of his economy pursue 

 for a while longer an unchanged course ; the boy does not become 

 a man till some years after puberty ; and the decline of his func- 

 tional manhood is so gradual that frequently it ceases only when 

 disease puts an end o a ripe old age. With the occurrence of men- 

 struation, on the other hand, at from thirteen to seventeen years 

 of age, subsequent to the acceleration of growth noted above 973, 

 which indeed appears preparatory to it, the girl almost at once 

 becomes a woman, and her functional womanhood ceases suddenly 

 at the climacteric in the fifth decennium. During the whole of 

 the child-bearing period her organism is in a comparatively 

 stationary condition. The variations in the yearly increment of 

 the girl before puberty though not so marked are more complex 

 than those of the boy, and she reaches the maximum of yearly 

 increment sooner than does he ; during this whole period indeed 

 she precedes him in growth and she has nearly reached her 

 maximum, while he is still continuing to grow. Her curve of 

 weight from the nineteenth year onward to the climacteric, 

 remains stationary, being followed subsequently by a late in- 

 crease, so that while the man reaches his maximum of weight 

 at about forty, the woman is at her greatest weight about fifty. 



Of the statical differences of sex, some, such as the formation 

 of the pelvis, and the costal mechanism of respiration, are directly 

 connected with the act of child-bearing, while others have only an 

 indirect relation to that duty ; and indications at least of nearly 

 all the characteristic differences are seen at birth. The baby boy 

 is heavier and taller than the baby girl, and the maiden of five 

 breathes with her ribs in the same way as does the matron of forty. 

 The woman is lighter arid shorter than the man, the limits in the 

 case of the former being from 1444 to 1-740 metres of height and 

 from 39-8 to 93\S kilos of weight, in the latter from 1467 to 

 1-890 of height, and from 491 to 98'5 kilos of weight. The muscu- 

 lar system and skeleton are both absolutely and relatively less in 

 woman, and her brain is lighter and smaller than that of man, 

 being about 1272 grammes to 1424. Her metabolism, as measured 



