626 



THE EXTERIOR OF THE HORSE. 



ceed the milk molars ; the last three are also called hind-molars, or persisting 

 molars. 



Fig. 296. 



A. Transverse section of the superior jaw, showing the third molar of the first dentition and 

 its replacing one, with the relations which they affect in tlie alveolus at the moment of eruption. 



B. Third superior molar of the second dentition covered by its milk-tooth. 



This set forms the branches of the dental arcade, which describe a line 

 slightly convex externally in the superior jaw, but straight in the inferior. The 

 superior molar arcade, a little wider than the inferior, surpasses the sides of the 

 latter. 



General Characters. — A molar of the second dentition resembles, in 

 general, a quadrangular prism flattened from within to without, save the first and 

 the sixtli, which have only three sides. We can recognize four faces and two 

 extremities. 



It presents, in situ, a free part or crown and an incased part or root : the 

 former projects above the level of the gums ; the second is deeply imjjlanted in 

 the alveolus. As there is no line of demarcation between these two parts, it is 

 useless to describe them separately. 



