706 REPRODUCTION. 



the lower jaw generally precedes by a short time that of the correspond- 

 ing teeth in the upper jaw. 



During the seventh year a change begins to take place by which the 

 first set of teeth arc replaced by the second or permanent set. The 

 anterior permanent molar tooth first shows itself just behind the pos- 

 terior temporary molar, on each side. This happens at about six and 

 a half years after birth. At the end of the seventh year the middle 

 incisors are thrown off and replaced by corresponding permanent teeth, 

 of larger size. At tho eighth year ci similar exchange takes place in 

 the lateral incisors. In tho ninth and tenth years, the anterior and 

 second molars are replaced by the anterior and second permanent bi- 

 cuspid teeth. In the twelfth year, the canine teeth are changed. In 

 the thirteenth year the second permanent molars show themselves ; and 

 from the seventeenth to the twenty-first year, the third molars, or 

 "wisdom teeth," emerge from the gums, at the extremities of the 

 dental arch. (Wilson). The jaw, therefore, in the adult condition, 

 contains three teeth on each side more than in childhood, making in 

 all thirty-two permanent teeth ; namely, on each side, above and 

 below, two incisors, one canine, two bicuspids, and three permanent 

 molars. 



The generative apparatus, which is inactive at birth, begins its func- 

 tional activity from the fifteenth to the twentieth year. The general 

 configuration of the body alters at this period, and the distinction be- 

 tween the sexes becomes more marked. The beard is developed in the 

 male ; and in the female the breasts assume the size and form charac- 

 teristic of puberty. The voice, which is shrill and sharp in infancy 

 and childhood, becomes deeper in tone, and the countenance assumes a 

 more sedate expression. After this period, the muscular system in- 

 creases still farther in size and strength, and the consolidation of the 

 skeleton also continues ; the bony union of its various parts not being 

 entirely accomplished until the twenty-fifth or thirtieth year. Finally, 

 all the organs of the body arrive at the adult condition, and the entire 

 process of development is then complete. 



