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HANDBOOK OF PHYSIOLOGY. 



The following formula shows, at a glance, the comparative arrange- 

 ment and number of the temporary and permanent teeth : 



Dec. Mo. Ca. In. Ca. Mo. 



(Upper 21412 =10 

 J 



Temporary Teeth. 



( Lower 



=20 



= 10 



Bicuspids 

 True or Prse- 



( Upper 3 

 ( Lower 3 



Permanent Teeth. 



21412 3 = 16 



From this formula it will be seen that the two bicuspid or praemolar 

 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. 



FIG. 165. -Part of the lower jaw of a child of three or four years old, showing the relations of 

 the temporary and permanent teeth. The specimen contains all the milk-teeth of the right side, 

 together with the incisors of the left; the inner plate of the jaw has been removed, so as to expose 

 the sacs of all the permanent teeth of the right side, except the eighth or wisdom tooth, which is 

 not yet formed. The large sac near the ascending ramus of the jaw is that of the first permanent 

 molar, and above and behind it is the commencing rudiment of the second molar. (Quam.) 



The temporary incisors and canines differ from their successors but 

 little except in their smaller size. 



The following tables show the average times of eruption of the Tem- 

 porary and Permanent teeth. In both cases, the eruption of any given 

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

 tooth of the upper. 



Temporary or Milk Teeth. 

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



