240 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



enamel. The temporal fossae are small, their zygomatic arches are slight, 

 and the maxillary condyle, instead of being transverse, as in the carnivora, 

 is anteroposterior, and articulates with the glenoid cavity in the same 

 direction, the articulating surface in these animals being a sort of 

 canal or gutter running from before backward (Figs. 88 and 89). The 

 arrangement of the articulation 

 of the upper and lower jaw, as 

 well as the mode of insertion 

 of the muscles, favor a backward 



Fig. 



86.— Head of Carnivora— Dog. 

 (Btclard.) 



Fig. 87.— Inferior Maxillary Bone of 



Carnivora— Polar Bear. (B6clard.) 



c, profile view of articular condyle of lower jaw (condyle of 



right side) ; ct, front view of same condyle. 



and forward motion of the lower jaw, which is, therefore, the character- 

 istic motion of rodents. 



Second. — In the ruminants the jaws are long and feeble, the canine 

 and upper incisor teeth are absent, while the molars are compound teeth 

 with a flat crown, with the enamel arranged in anteroposterior layers. 

 The condyle of the lower jaw articulates with a plane or almost convex 

 glenoid surface of the temporal bone, and this mode of articulation, 



Fig. 88.— Head of Rodent— Marmot. 

 {Beclard.) 



Fig. 89.— Inferior Maxillary Bone of 

 Rodent— Capybara: (Btclard.) 

 b, right articular condyle of lower jaw. 



together again with the arrangement of muscles, permits of a rotatory 

 motion of the lower jaw, which is therefore a characteristic trait in the 

 mastication of the ruminants (Figs. 90 and 91). 



Third. — In the solipedes and pachydermata three kinds of teeth are 

 present, and both of the above kinds of movement ; that is, rotation and 



