Chap, xi.] THE SCAPULA. 179 



injuries the angle may slip from beneath the muscle 

 and appear as a marked projection. This lesion is pro- 

 ductive of some loss of power in the limb. In many 

 cases where this accident is supposed to have occurred, 

 it is probable that the symptoms present are due 

 rather to paralysis of the nerve of Bell. 



Fractures of the scapula, and especially of 

 the body of the bone, are not common, owing to the 

 mobility of the part and the thick muscles that cover 

 in and protect its thinner portions. It rests also 

 upon a soft muscular pad, and derives, no doubt, 

 additional security from the elasticity of the ribs. 



The most common lesion is a fracture of the 

 acromion process. This is often but a separation of the 

 epiphysis. There are two, sometimes three, epiphy- 

 seal centres for the acromion. Ossification appears in 

 them about puberty, and the entire epiphysis joins 

 with the rest of the bone from the twenty-second to the 

 twenty-fifth year. Several cases of supposed fracture 

 of the acromion united by fibrous tissue are probably but 

 instances of an imperfectly-united epiphysis, and may 

 have been independent of injury. In fractures of the 

 process much displacement is quite uncommon, owing 

 to the dense fibrous covering the bone derives from the 

 two muscles attached to it. This dense periosteum also 

 explains the circumstance that many fractures are 

 incomplete and crepitus often absent. When the 

 fracture is in front of the clavicular joint, displace- 

 ment of the arm is impossible. When it involves the 

 joint, a dislocation of the collar-bone is common. 

 When behind the joint, the arm, having lost its 

 support from the thorax, is displaced in somewhat the 

 same way as obtains in the common fracture of the 

 clavicle. The coracoid process may present a genuine 

 fracture, or may be separated as an epiphysis. As an 

 epiphysis, it joins the main bone about the age of 

 seventeen. In spite of the powerful muscles attached 



