THE MOLARS. 



631 



Their bottoms, as well as the dental canal, are at first in 

 close proximity with the inferior border of the maxillary 

 bones; but as the teeth are shortened and pushed from 

 their sockets by the progress of age, the alveoli diminish 

 in depth and the aforesaid canal is elevated in almost the 

 same proportion. This fact is particularly observable in 

 the first three or four molars. It can be understood, from 

 this, that the border of the inferior maxillary bone will be 

 thicker as the animal is younger, or as the teeth are more 

 deeply implanted in their cavities of reception, and, con- 

 versely, thinner as the animal grows older. 



Separation of the Two Inferior Molar Arcades. 

 The inferior molar arcades, considered as a whole, are 

 rectilinear and divergent behind. The following measure- 

 ments can be easily compared with those which have already 

 been given for the superior arcades of the same horse : 



1st. The separation of the anterior border of the first 

 molar from the corresponding border of the opposite tooth 

 was 0.043 m. 



2d. The separation on a level with the middle part of 

 the third molar (measured from the outside) was found to be 

 0.072 m. 



3d. Finally, at the level of the posterior border of the 

 last molar it measured 0.077 m. 



Extent of the Table of the Six Inferior Molars 

 in the Antero-Posterior Sense. The total length of 

 the arcade, in the horse in question, was 0.164 m., which 

 was shared by each tooth in particular, as follows : 



1st 0.029 m. 



2d 0.027m. 



3d 0.027m. 



4th 0.025m. 



5th 0.025 in. 



6th . 0.031 m. 



0.164 m. 



C. Development and Structure of the 

 Molars. 



These teeth have the same general organization as the 

 incisors, but the substances constituting them have a very 

 complex arrangement, which must be examined in the 

 molars of both jaws. 



i. Development. 



Superior Molars. If a superior molar be viewed 

 in the interior of the sac in which it appears, it is ob- 

 served that prominent papillae, two in number, penetrate 

 the thickness of its free extremity, while at the incased 

 extremity only one is found, but which is much more com- 



