ERUPTION OF THE PERMANENT TEETH 127 



stature. The eruption of the teeth through the gums is but 

 evidence of their previous rapid development, and there is 

 doubtless a period of rest throughout the body between the 

 periods of rapid development of the teeth and the periods of 

 rapid growth in stature. 



Others have repeatedly demonstrated that the six months 

 following birth is a period of rapid increase in length of the 

 infant, which is followed by the eruption of the temporary teeth, 

 all of which are through the gums by the age of three years. 

 After this there is a period of rest which is followed by a second 

 period of growth in stature about the age of five years, suc- 

 ceeding which the permanent teeth begin to develop, and this 

 development is most rapid about the age of 7 years. This is 

 followed by the third period of rapid growth in stature about the 

 age of 8 years after which comes a period of rest and then the 

 second acceleration in the eruption of the permanent teeth occurs 

 between 10 and 11 years. The final rapid growth in stature 

 comes after this at about 12 years of age, and immediately pre- 

 cedes puberty. Following puberty the increase in stature and 

 the eruption of the teeth are delayed, especially in the girls. 

 However, the third period of the acceleration in the eruption of 

 the teeth (second period of acceleration in the eruption of the 

 permanent teeth), the girls are about one year earlier than the 

 boys, and the period of growth following this is about two years 

 earlier in the girls than in the boys; (see The law of alternation 

 in development, p. 137). 



Resume. After this brief consideration of the average or 

 'mean,' time of eruption of the permanent teeth, the 'median,' 

 the 'mode' and the 'extremes,' as well as the periods of accelera- 

 tion and retardation in the eruption, it is to be noted that the 

 second teeth begin to erupt about 5 years of age, slightly earlier 

 among the girls than among the boys and earlier among the 

 Filipinos than among the Germans and the Americans, and 

 latest of all among the Germans. 



The girls are more precocious in the periods of acceleration of 

 the eruption of the teeth than the boys, as well as in the average 

 number of teeth, the 'median' and 'extremes' at any age. The 



