90 THE SURGICAL ANATOMY OF THE HORSE 



Each ramus is a laterally compressed plate, which presents a well- 

 marked bend, dividing the plate into two portions, one of which is 

 disposed vertically and the other horizontally. The width of the plate 

 is greatest across the bend. For descriptive purposes the ramus may 

 be said to possess two surfaces, two borders, and two extremities. 



The outer surface of the horizontal portion is smooth and convex, 

 but that of the vertical portion is depressed, and presents a number of 

 rough markings for the attachment of the masseter muscle which clothes 

 this part of the ramus. Near its junction with the body the ramus 

 presents on this aspect the large mental foramen which communicates 

 with the inferior dental canal, and through which the mental nerve 

 and vessels pass. 



The inner surface of the ramus is slightly depressed in its horizontal 

 portion. The genio-hyoideus and genio-glossus muscles are attached to 

 this surface of the bone close to its junction with the body, and the 

 mylo-hyoid muscle is attached to a faint marking near the alveolar 

 edge. On the vertical portion the surface is depressed and roughened for 

 the attachment of the internal pterygoid muscle, and slightly behind its 

 anterior border is a large foramen, which is the entrance to the inferior 

 dental canal through which the inferior dental branch of the inferior 

 maxillary division of the fifth nerve, with its accompanying artery, passes. 



The superior or anterior border of the horizontal portion presents 

 the alveoli for the six molar teeth, and where this border is continued 

 in front of the vertical portion it is thin and sharp. To it, immediately 

 below the coronoid process, the temporal muscle is attached. 



The horizontal and vertical portions of the posterior or inferior 

 border are sharp and well defined, but where these portions become 

 continuous with one another the border becomes very much thickened 

 and roughened, and this portion constitutes what is known as the angle 

 of the jaw. 



The upper extremity of the bone carries the coronoid process and 

 the condyle, with the intervening sigmoid notch. 



