OBLITERATION OF SUTURES IN SKULL 497 



Group III. In this group the eruption of the permanent 

 central incisor had taken place. There were 168 of such skulls 

 belonging to children aged about 7 or 8 years. The dental 

 formula is as follows: 



I. i. c. m. m. M. 



Group IV. This group contains 157 infant skulls in which 

 the lateral permanent incisor has made its appearance corre- 

 sponding with the age of 8 or 9 years. The dental formula of 

 this series is to be written: 



I. I. c. m. m. M. 



Group V. In this set were included the 109 skulls in which 

 the first milk-molar was lost, and the dental formula is the 

 following : 



1. 1, c. P. m. M. 



Such a set of teeth corresponds with an age of 9-11 years. 



Group VI. Includes 203 skulls between 11 and 13 years, in 

 which the second premolar and the canine are present. The 

 order of eruption of both of these teeth is not a constant one. 

 Although in a considerable majority of skulls the second pre- 

 molar precedes the canine, yet there were a certain number in 

 which the eruption of the second premolar evidently succeeds 

 the eruption of the canine. Therefore I have included all 

 these skulls in one set. Its dental formula is as follows: 



I. I. c. P. P. M. 



Group VII. This last group contains all the skulls (58 in num- 

 ber) with a complete set of teeth, save the third molar. These 

 skulls, of w^hich the dental formula is 



I. I. C. P. P. M. M. 



come from individuals who died between the age of 13 years 

 and the adult state. 



I have found in my whole collection but three skulls, not 

 yet completely developed, in which the eruption of the third 

 molar had already taken place. It must therefore be considered 

 as a rule that the wisdom tooth makes its eruption after the 



