38 



ANATOMY 



The rate at which the teeth increase in length during their 

 formative period and prior to attrition is given in the following 

 table : 



Average growth of upper incisor 0.52 mm. and of lower incisor O.i 

 day. 



mm. per 



TABLE 16 



Naso-occipital length 



Interzygomatic 1 



Upper diastema 



Upper incisor — total length 



Upper incisor — extra alveolar 



length 



Lower diastema 



Lower incisor — total length 



Lower incisor — extra alveolar 



length 



23 



DAYS 



29.7 



13.7 



7.4 



12.8 



5.1 



4.6 



18.1 



6.5 



41 



DAYS 



mm. 



32.5 

 14 

 9.5 

 15 



5.5 

 5 

 21.7 



10 



WEEKS 



39 

 14.5 

 10 

 18.3 



7 



5.6 

 25.5 



10.5 



15 



WEEKS 



40 

 14.6 

 11.4 

 20.3 



8.4 

 6 

 26.4 



11.4 



5 



MONTHS 



43 

 15.4 

 12.3 

 23.3 



8.7 



6.7 



29.4 



11.6 



44 

 15.1 

 12.5 

 23.7 



9 



7 



29.9 



12 



10 



MONTHS 



46.5 

 15.5 

 13 

 26.2 



9.3 



6.8 



31.3 



12.4 



1 Same as 'squamosal distance,' figure 1, p. 36. 



