628 



THE EXTERIOR OF THE HORSE. 



vj^^^w^K v 



cavities also disappear. It is then that a verita- 

 ble dental table manifests itself; but, far from 

 remaining plane, it soon presents in relief, upon 

 the middle part of the branches of the $5, two 

 transverse crests, sometimes feebly marked, which 

 determine there certain planes, alternately oblique 

 in opposite directions, and render it much more 

 adapted to crush the alimentary substances. 



The incased extremity, or root, is primitively 

 provided with several openings leading into cavi- 

 ties in the interior of the tooth, and containing 

 the pulp, rich in blood-vessels and nerves. Later, 

 a variable number of prolongations develop at 

 this extremity ; at this period said extremity is 

 composed of three roots in the first and last molars, 

 and four in all the others. According to Girard, 

 these divisions of this extremity begin to develop 

 at the age of five years, and become more strongly 

 characterized with the advance of age. 



Antero-posterior Diameter of the Ta- 

 bles. If the six molars occupy, for example, a 

 length of 0.166 m., in an antero-posterior sense, 

 it should not be believed that all the teeth share 

 equally in its production. This diameter dimin- 

 ishes, on the contrary, gradually from the first to 

 the sixth, inclusive. In fact, below are the figures 

 which we have obtained from the superior arcade 

 of a horse six or seven years old, whose teeth 

 have been measured in the middle part of their 

 surface of friction (Fig. 298) : 



1st 



2d 0.028 m. 



3d 0.027 m. 



4th 0.026m. 



5th 0.025m. 



6th . . . 0.024 m. 



0.166 m. 



Transverse Diameter of the Tables. 

 The teeth, in this respect, are thicker as they are 

 examined more towards the middle of the arcade 

 to which they belong. 



Separation of the Two Branches of 

 the Superior Molar Arcade. It suffices, in 

 order to give an idea of it, to measure this separa- 

 tion at three points : at the middle and at each 

 extremity. 



1st. In front: from the anterior border of 

 the first molar to the corresponding part of the 

 opposite tooth, 0.064 m. 



2d. At the middle: from the median emi- 



