34 



ANLMi\L J)Jv\TISTRV 



posteriorly, 'llic width between the arcades is 83 milli- 

 meters at the sixth molars, 75 millimeters at the fourth, and 

 57 millimeters at the first. They are from 18 to 20 centi- 

 meters lont^: and average 25 to 28 millimeters wide. 



The inferior arcades are more on a straight line than the 

 superior ones. They are but slightly curved outward at the 

 fourth and fifth molars, while at the second and third they 

 may even present a slight inward curvature. Like the su- 

 perior, they have a uniform width with the exception of the 

 pointed extremities. The width between the arcades is 75 

 millimeters at the sixth molars, 60 millimeters at the fourth 

 and about 50 millimeters at the first. They are from 18 to 

 20 centimeters long and average 17 to 20 millimeters wide. 



;7 N M. 



Fig. 20.\. 

 Table Surface of an Inferior Molar, with Measurement. 



In situ the molars present four arcades — right and left 

 superior and right and left inferior — each containing six 

 teeth, juxtaposited so closely as to give the impression of 

 being a single body. The juxtaposition of the molars is one 

 of the important features of tlie dental mechanism of her- 

 bivorous animals. This feature adds materiall}'- to the for- 

 mation of a perfect, as well as a stable, grinding apparatus. 



Each arcade is from t8 to 20 centimeters in length. 



THE PERMANENT INCISORS OF RUMINANTS. 



Ruminants have but one incisor arcade — the inferior — 

 the superior l>eing replaced by a dense pad of connective 

 tissue. The incisors are eight in number, identified, count- 



