PREHENSION OF FOOD. 235 



long enough to reach the ground : the lips then carry the grass between 

 the teeth. A horse cannot live on very bare pasture, since the grass must 

 be long enough to be grasped by his prehensile upper lip ; and he there- 

 fore cannot enter into competition with close-biting animals, such as 

 sheep, since they will deprive a field of the best and youngest plants as 

 fast as they come through the ground. 



In the ox the tongue is the main organ of prehension of food, since 

 the upper lip is short, has but slight power of motion, and is blended 

 with the cartilaginous, solid muzzle, which is covered by a thick, secret- 

 ing membrane. The tongue of the ox is, however, provided with great 

 mobile power; it may project far from the mouth, and, curving like a 

 sickle, the animal may seize and draw food into the mouth. It is rough; 

 pointed, covered with recurved, sharply -pointed papillae so as to strengthen 

 its grasp on bodies with which it comes in contact. In grazing, the 

 tongue is protruded, curved around the grass, which is thus drawn into 

 the mouth and then cut by the pressure of the lower chisel-like incisors 

 against the elastic pad which occupies the position of the upper incisors. 

 The ox also is unable to feed on very short grass. 



In the sheep and goat the upper lip has a certain degree of mobile 

 power, more than that possessed by the ox, but not as great as that of 

 the horse. It, however, is unable to grasp food., and merely aids the 

 incisors and tongue in grazing. The tongue is also more freely mova- 

 ble than in the horse, and the combination of the mobile lip and prehen- 

 sile tongue enables it to feed close to the ground. Here also the upper 

 incisors are absent, and grass is cut by the pressure of the lower incisors 

 against the cartilaginous elastic pad of the upper jaw. 



The pig in its native state feeds by rooting out plants, roots, and 

 nuts from the ground, and is provided with a strong and mobile snout, 

 having a bony and cartilaginous basis, and moved by powerful muscles. 

 It acts like a spade in digging up the ground, while the lower lip is short 

 and pointed, and is enabled to gather food loosened by the digging action 

 of the snout. The passing of a ring through the snout of a hog entirely 

 destroys its natural methods of collecting food, and animals so treated 

 are dependent upon artificial feeding, and if left to their own efforts 

 would starve. Pigs are omnivorous, but yet their incisor teeth are so 

 shaped as to prevent them from grazing. 



Carnivorous animals, such as the dog and cat, feeding principally on 

 meat and animal matters, fix their food with the forelegs, grasp it between 

 their powerful jaws, using here mainly the canine teeth, and lacerate it 

 by a backward jerk of the head. They are biting animals, and as a con- 

 sequence their cheeks are loose and ample, their mouths open widely, 

 and their teeth are pointed and curved back. The lower jaw only is used; 

 and it is said that when the lower jaw is fixed carnivorous animals, 



