688 PUBERTY. [BooK iv. 



and the temporary dentition is completed by the appearance of the 

 second molars usually before the end of the second year. 



About the sixth year the permanent dentition commences by 

 the appearance of the first permanent molar beyond the second 

 temporary molar; in the seventh year the central permanent 

 incisors replace their temporary representatives, followed in the 

 next year by the lateral incisors. In the ninth year the temporary 

 first molars are replaced by the first bicuspids, 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. 



Shortly after the conclusion of the permanent dentition (the 

 wisdom teeth excepted) the occurrence of puberty marks the begin- 

 ning of a new phase of life ; and the difference between the sexes, 

 hitherto merely potential, now becomes functional. 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 characteristic 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 spermato- 

 zoa, are striking features, yet they are after all superficial. The 

 curves of his increasing weight and height, and of the other 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, 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. 

 While before the age of puberty up to about the eleventh or 

 twelfth year, the girl is lighter and shorter than the boy of the 

 same age, in the next few years her rate of growth exceeds his ; but 

 she has then nearly reached her maximum, while he continues 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 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 



