ERUPTION OF THE PERMANENT TEETH 



397 



by the wear of the anterior 

 edge, which is well marked 

 in the drawing below (fig. 

 609). 



Meanwhile the first and 

 second pre-molars (temporary) 

 have been passing through the 

 same changes as those which 

 have been described in the 

 four central temporary inci- 

 sors, and at the age of three 

 years there are eight new 

 molar teeth, two on each side 

 in both jaws, top and bottom. 

 These recently-cut permanent 

 pre-molars are distinguished 

 by their surfaces being com- 

 paratively free from wear, while the molars behind them are worn quite flat. 



Fig. 609. Incisors of Horse at three years 



Fig. 610. Molars of Horse at two years and seven months 



The illustration (fig. 610) shows the state of the molars at two years 

 and seven months. 



The next changes affect the lateral temporary incisors, top and bottom, 



Fig. 611. Molars of Horse at three years and eight months 



and the third pre-molar (temporary), and include the eruption of a sixth 

 molar at the back of the mouth, which is cut at the same time as the third 



VOL. III. 



91 



