ERUPTION OF THE PERMANENT INCISORS. 



65 



rior borders at six months and are leveled at ten months ; tlie 

 arch is broken in the centre and loses its continuity at the 

 first intermediate at one year, second intermediate at fil'teeii 

 months, and at the corner teeth at eighteen to twenty months. 



Fig. I(i2. 

 Two years, tt, external lace, b, internal face. 



THIRD PERIOD — ERUPTION OF THE PERMANENT INCISORS. 



Twenti/ Months. — At this time the milk-pinchers are re- 

 placed by the permanent ones, which protrude somewhat 

 obliquely, but soon assume their natural position and arc in 

 place at two years. (Fig. 162.) 



