CH. V.] 



THE TEETH 



51 



the course of a few years shed and replaced by the second or per- 

 manent set. 



The temporary or milk teeth are ten in number in each jaw, 

 namely, on either side from the middle line two incisors, one canine, 

 and two deciduous molars, and are replaced by ten permanent teeth. 

 The number of permanent teeth in each jaw is, however, increased to 

 sixteen by the development of three molars on each side of the jaw, 

 which are called the permanent or true molars. 



The following tables show the average times of eruption of the 

 Temporary and Permanent teeth. In both cases the eruption of any 

 given tooth of the lower precedes, as a rule, that of the corresponding 

 tooth of the upper jaw. 



Temporary or Milk Teeth. 

 The figures indicate in months the age at which each tooth appears. 



Permanent Teeth. 



The age at which each tooth is cut is indicated in this table in years. 



The times of eruption given in the above tables are only approxi- 

 mate: the limits of normal variation are tolerably wide. Certain 

 diseases affecting the bony skeleton, e.g. Kickets, retard the eruptive 

 period considerably. 



It is important to notice that it is a molar which is the first tooth 

 to be cut in the permanent dentition, not an incisor as in the case of 

 the temporary set, and also that it appears behind the last deciduous 

 molar on each side. 



The third molars, often called Wisdoms, are sometimes unerupted 

 through life from want of sufficient jaw space and the presence of 

 the other teeth ; cases of whole families in which their absence is a 

 characteristic feature are occasionally met with. 



