THE SKELETAL SYSTEM 35 



interparietal, parietal, frontal, and temporal. The first four are 

 single, the others paired.^ They enclose the cranial cavity. 



The bones of the face are of most importance to the horseman, 

 for they carry the teeth. They are the maxiUa, premaxilla, pala- 

 tine, pterygoid, nasal, lacrimal, malar, superior and inferior tur- 

 binals, vomer, mandible, and hybid. The last three are single, the 

 others paired. They form the walls of the oral and nasal cavities. 

 The shape of the nose and the coarseness or fineness of the head 

 is determined by these bones. 



The maxillae are the principal bones of the upper jaw and 

 carry the upper molar teeth. They are situated on the lateral as- 

 pects of the face. Each presents two surfaces. The external 

 surface is convex, especially in the young animal. The prominent 

 ridge noted on this surface is the facial crest. A little above and in 

 front of this crest is the infra-orbital foramen. The internal sur- 

 face is concave, smooth, and forms part of the wall of the nasal 

 cavity. A ridge gives attachment to the inferior turbinated bone, 

 above which is the lacrimal canal. Springing medially from the 

 lower part is the palatine process, which forms a large portion of the 

 hard palate and meets its fellow at the median plane. The inferior 

 border has six alveoli for the upper molar teeth. 



The premaxillae are situated in front of the maxillse. They are 

 strongly developed anteriorly. Each has three alveoli for incisor 

 teeth. The palatine processes project backward to form the an- 

 terior part of the roof of the mouth. 



The palatine bones are small and may be considered as exten- 

 sions to the hard palate. 



The pterygoid bones are thin, strap-like attachments to the 

 palatine bones. 



The nasal bones form most of the roof of the nasal cavity. The 

 dorsal surface is convex, the ventral concave and provides attach- 

 ment for the superior turbinated bone. The anterior extremity is 

 pointed, thin, and free. 



The lacrimal bones are placed one in front of each eye. 



The malar bones are situated below the lacrimal bones and 

 correspond to the cheek bones of man. 



The turbinated bones, four in number, two on each side, divide 

 the nasal cavity into three passages. The bones are very delicate 



' The student should learn the relative positions of these bones, but need 

 not be required to describe each in detail. 



