THE EUMINANTS. 151 



some safe retreat, where they assist the digestive 

 process by giving the grasses and leaves consumed 

 a subsequent crunching and chewing. The Rumin- 

 ants do not bite off the plants, but tear them off, 

 in doing which the tongue plays an important part 

 as an organ for grasping, especially when long 

 grasses and branches have to be dealt with. In 

 this mere tearing off of grasses, &c., the incisors of 

 the upper jaw can be dispensed with ; it may be 

 said that with the development of meadow plants 

 and pastures, these teeth have in course of time 

 become superfluous. Only animals of the Camel 

 species show rudiments of the upper incisors, and 

 in addition to this case, canines have been pre- 

 served by the musk-deer. The crowns of the molars, 

 as a rule, show two transverse ridges, and, moreover, 

 the upper and lower molars fit in such a manner 

 that they can glide over one another from right to 

 left and also in a horizontal manner, as may be 

 seen in any ox or sheep * chewing the cud.' This 

 movement of chewing is rendered possible by the 

 condyle of the lower jaw not being sunk into a 

 transverse socket of the temporal bone, as in the 

 case of the Carnivora, or into a furrow running 

 parallel with the axis of the skull so as to move 

 backwards and forwards, as in the Rodents, but by 



