1150 DENTITION. [Boon iv. 



lowed in the next year by the lateral incisors. In the ninth 

 year the temporary first molars are replaced by the first bi- 

 cuspids, and in the tenth year the second temporary molars are 

 similarly replaced by the second bicuspids. The canines are 

 exchanged about the eleventh or twelfth year, and the second 

 permanent molars are cut about the twelfth or thirteenth 

 year. There is then a long pause, the third or wisdom tooth 

 not making its appearance till the seventeenth, or even twenty- 

 fifth year, or in some cases not appearing at all. 



717. 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 

 appearance of active spermatozoa, are striking features, yet they 

 are after all superficial ; and though, as we have seen ( 713), 

 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 functional manhood is so gradual that 

 frequently it ceases only when disease puts an end to a ripe old 

 age. With the occurrence of menstruation, on the other hand, 

 at from thirteen to seventeen years of age, subsequent to the 

 acceleration of growth rioted above 713, 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 increase, 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 di- 

 rectly 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. 



