IN THE LOWER ANIMALS, ETC. 



245 



If we watch a sheep grazing, we may see how 

 admirably the whole mechanism works together. 



I 



"SiqAI.— Molar Teeth of Sheep. 



A. Grinding surf ace of upper Teeth, left side, showing the convexity of enamel folds 

 directed inwards. 



B. Showing external and grinding surfaces of lower Teeth {left side), the enu/nel folds 

 being directed outwards. 



The prolonged upper lip aids the tongue in sweep- 

 ing a tuft of grass into the vice formed by the 

 cutting teeth of the lower, and the unarmed front 

 of the upper jaw, while the upward jerk helps to 

 sever the herbage from the roots. 



The process of ruminating also supplies an in 

 teresting subject for observation, when the sheep 

 are lying down in the fold, in the act of masti- 

 cating the food previously cropped, and stored in 

 their first stomach. 



The low murmur of so many sets of animated 

 millstones, when listened to in the stillness of a 



