222 THE ANATOMY OF THE HORSE. 



times described as distinct posterior and external ligaments. The first of 

 these stretches from the post-glenoid process to the inferior maxilla 

 below and behind the condyle. The second is attached above to the 

 lower edge of the zygomatic arch, from which it extends downwards and 

 backwards to be fixed to the inferior maxilla below and external to the 

 condyle. 



The Interarticular Fibro-cartilage should be exposed by removing 

 the capsular ligament on the outer side. The cartilage extends com- 

 pletely across the joint, which it divides into an upper and a lower 

 cavity. Its upper surface is a cast of the temporal articular surface, 

 while its lower is moulded on the condyle of the jaw. 



Synovial Sacs. The upper of these belongs to the articulation 

 between the fibro-cartilage and the temporal articular surface ; the 

 lower to the articulation between the fibro-cartilage and the condyle. 



Movements. These are — depression, elevation, protraction, retraction, 

 and lateral movement of the inferior maxilla. 



When the jaw is depressed, as in opening the mouth, the condyles of 

 both jaws are carried forwards, taking with them the fibro-cartilages, 

 until they lie under the condyle of the temporal articular surface ; and 

 at the same time the maxillary condyles move in the depression on the 

 under surface of the interarticular fibro-cartilage, rotating around a 

 transverse axis. When the lower jaw is protracted the movement 

 consists principally in anteroposterior gliding between the temporal 

 articular surface and the interarticular cartilage ; and when the same 

 movement is executed alternately on opposite sides a lateral, grinding 

 action is produced. 



THE CAVITY OF THE NOSE (FIGS. 27 AND 28). 



Directions. — Make, with the saw, an antero-posterior vertical section 

 of the head, a little to one or other side of the mesial plane, taking the 

 mesial sutures on the front of the head as a guide. 



The cavity of the nose is the first segment of the air-passages, and is 

 thus a part of the respiratory apparatus. It is also in part devoted to 

 the sense of smell, the olfactory nerve being distributed over a part of 

 its boundary walls. It is a large tubular passage tunnelled through the 

 skull in front of the mouth (the head being vertical). A mesial partition 

 — the septum nasi — divides the passage longitudinally into the right 

 and left nasal fossce. Each nasal fossa may be described as having 

 anterior, posterior, and lateral walls, and a superior and an inferior 

 extremity. 



The Anterior Wall, sometimes termed the Roof, is narrow and formed 

 by the frontal and nasal bones. 



The Posterior Wall, sometimes termed the Floor, is considerably more 



