158 THE HORSE 



maxillary {i), which, uniting with the nasal bone and the 

 pre-maxillary, completes the framework of the nose. The 

 lower jaw consists of only two bones, the inferior maxillaries, 

 which are rounded at the hinder extremity of the jaw, and 

 terminate in two processes directed upwards. One, the 

 condyloid process, articulating with the temporal bone, 

 forms the hinge on which the whole lower jaw moves. The 

 other, the coronoid, passes under the zygomatic arch, and 

 receives the lower end of the large temporal muscle, which 

 arises from the parietal bone and is principally concerned 

 in moving the jaw when masticating food. 



There are two small bones not visible externally, the 

 sphenoid and ethmoid, under the parietal in the lower part 

 of the cranium, which serve to connect the principal 

 bones of the skull. 



The Vertebra. 



The vertebrae of the neck are seven in number, and 

 comprise (Plate IV.) — 



1. Atlas 



2. Dentata 



3. Third 



4. Fourth ^ Cervical vertebrae. 



5. Fifth 



6. Sixth 



7. Seventh 



/ 



The atlas is a ring-shaped bone, articulating with the 

 skull. It moves freely on the dentata, and on the peculiar 

 articulation of these two vertebrae largely depends the 

 power of turning the head. The remaining five bones, 

 resembling one another, call for no comment. They have 

 various processes to which the muscles and ligaments of 

 the neck are attached. 



The dorsal vertebrae, those of the back, are eighteen in 

 number, and support the ribs ; whilst those of the loins, the 

 lumbar, which are situated between the ribs and the haunch- 

 bones, are six, the whole amounting to twenty-four, which 

 are invariable. The normal number of ribs is eighteen, 

 though sometimes nineteen occur, and occasionally even 



