70 



HANDBOOK OF PHYSIOLOGY. 



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 formula shows, at a glance, the comparative arrange- 

 ment and number of the temporary and permanent teeth : 



MOLARS. 



2 



CANINE. 

 1 



Temporary Teeth. 



MIDDLE LINE OF JAW. 



INCISORS. 

 2 



INCISORS. 



2 



CANINE. 

 1 



MOLARS. 



2=10 



2=10 



= 20 



Permanent Teeth. 



MIDDLE LINE OP JAW. 



From this formula it will be seen that the two bicuspid or pre-molar 

 teeth in the adult are the successors of the two deciduous molars in the 

 child. They differ from them, however, in some respects, the temporary 

 molars having a stronger likeness to the permanent than to their imme- 

 diate descendants the so-called bicuspids, besides occupying more space 

 in the jaws. 



The temporary incisors and canines differ from their successors but 

 little except in their smaller size and the abrupt manner in which their 

 enamel terminates at the necks of the teeth, forming a ridge or thick 

 edge. Their color is more of a bluish-white than of a yellowish shade. 



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. 



