Chap, xiii.] REGION OF ELBOW. 249 



line is almost wholly within the capsule, it follows 

 that but little displacement, other than a slight 

 movement backwards, is consequent upon the separa- 

 tion of the mass. 



Fractures of the olecranoii are commonly clue 

 to direct violence, and in a few cases to severe indirect 

 violence applied to the lower end of the humerus or 

 upper end of the ulna. Instances of fracture by 

 muscular action are few, and open to some question. 

 The fracture is most commonly met with about the 

 middle of the process, just where it begins to be 

 constricted, and is usually transverse in direction. The 

 amount of displacement effected by the triceps varies, 

 and depends upon the extent to which the dense 

 periosteum about the process and the ligaments that 

 are attached to it are torn. The olecranon is developed 

 mainly from the shaft of the ulna. There is a small 

 epiphysis, however, at the summit of the process which 

 joins the rest of the olecranon at the age of seventeen. 

 It is a mere shell of bone. In young subjects this 

 scale-like epiphysis may be separated by violence, or 

 the cartilaginous olecranon may be dissevered from the 

 rest of the bone. The common fracture of the adult 

 olecranon does not follow the epiphyseal line. 



Fraetiire of the coronoid process is an 

 extremely rare accident. It is impossible to under- 

 stand how the process can be torn off by the action 

 of the brachialis anticus, as some maintain, since that 

 muscle is inserted rather into the ulna at the base of 

 the projection, than into the process itself. Nor can 

 it be separated as an epiphysis, as supposed by others, 

 since it does not exist as such. 



Fractures of the head or neck of the radius 

 are rare, and occur usually with dislocation or other 

 severe injury. The head is commonly found split or 

 starred, and the lesion, if limited to the head, could 

 hardly be diagnosed. The upper epiphysis of the 



