126 ROBERT BENNETT BEAN 



and girls is still less, and they have a greater number of teeth 

 present than either the German or Americans at the age of 11 

 years, 24.3 and 27.0 for the boys and girls respectively. 



The Filipinos are much more precocious than either the Ger- 

 mans or Americans in the eruption of the permanent teeth, and 

 there is little difference between the boys and girls in the number 

 of teeth present at each age. The Americans are a little more 

 precocious than the Germans in the eruption of the permanent 

 teeth, and the difference between the boys and girls is greater 

 among the Americans than among the Germans and Filipinos. 



About the age of 15 years the children of both sexes in all 

 the groups have nearly the same number of teeth, and after this 

 age the German and American children maintain the same num- 

 ber of teeth up to the time at which the records cease (18 years), 

 but the Filipino children continue to gain in the number of their 

 teeth to the age of 20 and bieyond, although the majority of the 

 Filipinos have acquired the complete set of 32 teeth at the age 

 of 20 years. This is due to the early eruption of the third molars 

 among the Filipinos (begins at 13) and their later eruption among 

 the Germans and Americans (begins at or after 16). 



Sixty odd negro boys and girls, mostly mulattoes, were exam- 

 ined at Ann Arbor, and it is found that the negro boys and the 

 American boys are almost parallel in the time of the eruption of 

 their teeth, and the negro girls are only slightly more precocious 

 than the American girls, 



2. The alternation of growth in stature and the eruption of the 



permanent teeth 



The eruption of the permanent teeth does not occur with the 

 same rapidity at each age, but there are waves of eruption of the 

 teeth like the waves of growth, although the two are not syn- 

 chronous. The periods of acceleration in the eruption of the 

 permg^nent teeth occur about the ages of 7 and 11 years, and the 

 periods of retardation follow those of acceleration. It will be 

 seen that the periods of acceleration in the eruption of the per- 

 manent teeth initiate or precede the periods of rapid increase in 



