ERUPTION OF THE PERMANENT TEETH 115 



can and German parentage. The titles American and German 

 will be used for the twQ groups. When taken together the 

 German and American children will be called European. Chil- 

 dren were grouped as German if two grandparents or if either 

 parent came from Germany, and whenever the name was Ger- 

 man and the parentage was not given the child was included in 

 the German group, although there were only a few records of 

 this kind. There is a large colony of Germans both in the town 

 of Ann Arbor and in the adjacent country and the majority of 

 the Germans included in the records are of pure German ex- 

 traction. A large number of children of the teaching staff at 

 the University of Michigan are included in the American group 

 and a large number of rural children are included in the German 

 group. The whole lot of children may be called sub-urban. 



The Manila school children were examined by myself in 1907- 

 08 at the Normal and Trade schools, where pupils from all parts 

 of the Philippine Archipelago come to be educated as teachers 

 and mechanics, carpenters, etc. The young children attend 

 classes taught by the older ones at the Normal School and are 

 necessarily from Manila and vicinity. The majority of the chil- 

 dren are mestizos, mixed Spanish, Chinese and Filipino, and 

 represent the littoral population of the archipelago fairly well. 

 A few individuals are probably of pure Spanish extraction. No 

 attempt was made to segregate the mestizos or those of Chinese 

 or Spanish extraction from the presumably pure Filipinos be- 

 cause any such attempt is necessarily imperfect and will be so 

 until we understand better than we do at present the workings 

 of Mendelian heredity in man. 



METHODS 



The age of the children was obtained from each individual and 

 verified as far as possible through the teachers. In Manila the 

 school registers were also examined and the age verified in this 

 way. Discrepancies occur in spite of all efforts to avoid them, 

 but I believe nearly all the ages are exact, and the few that may 

 not be are approximately correct. The year and the month of 



