162 PHYSIOLOGY AT THE FARM. 



joined in the median line, so as to form the posterior part of 

 the roof of the mouth and of the floor of the nostrils, the rest 

 of the roof of the mouth being formed by the intermaxillary or 

 os incisivum, and the palatine plate of the superior maxillary 

 bone. The lower jaw in the pig has its ascending portion low 

 and broad ; the coronoid process very short, and far distant 

 from the condyloid process. The condyloid process is narrower 

 from without inwards, and broader from before backwards, than 

 in ruminant animals. The angle of the jaw also is higher and 

 thicker than in the ox and sheep. 



Mouth. The mucous membrane of the mouth in the pig is 

 smooth, but the surface of the palate is marked by several trans- 

 verse prominences of considerable size. The lips of the pig re- 

 semble those of the ruminants, with this difference, that the upper 

 lip advances somewhat farther forward. Owing to the kind of 

 food, roots in particular, on which the pig naturally feeds, the 

 extremity of the muzzle is transformed into a peculiar digging 

 organ the jaws are contracted, and the nasal bones, as already 

 said, reach the level of the incisor teeth. The cartilaginous 

 partition of the nostril contains, between the nasal spine and 

 the intermaxillaries, a small bone which is named the spade - 

 bone. The upper lip is confounded with the fleshy prolonga- 

 tion in which the nostrils are pierced, which prolongation is 

 moved by powerful muscular fibres, and terminated by a kind 

 of disc with a well-marked border. The snout seems to be 

 insensible at its extremity, and therefore well adapted for bur- 

 rowing in the earth. Eunning down the nose and spread out 

 over the nostril is a large plexus of nerves, which, doubtless, 

 enables the pig to direct its digging operations with the greater 

 certainty. The olfactory nerve, too, is large, holding a middle 

 place between that nerve of sense in the herbivora and in the 

 carnivora. It is larger comparatively than in the ox, and few 

 animals except the dog are gifted with a more acute sense of 



