Chap, xi.] THE SHOULDER JOINT. 2 1 9 



also more or less unduly tense, the elbow is found 

 flexed and the fore-arm supinated. In every form 

 there is some increase in the vertical circumference of 

 the axilla, since the head, having left theglenoid fossa, 

 must occupy some part comprised within that cir- 

 cumference. Again, Dr. Dugas has pointed out that 

 " if the fingers of the injured limb can be placed by 

 the patient, or by the surgeon, upon the sound 

 shoulder while the elbow touches the thorax (a con- 

 dition that obtains in the normal condition of the 

 joint), there can be no dislocation ; and if this can- 

 not be done there must be one, for no other injury than 

 a dislocation can induce this physical impossibility." 

 This depends upon the fact that in consequence of the 

 rotundity of the thorax it is impossible for both ends 

 of the humerus to touch it at the same time, and in 

 luxation at the shoulder the upper end of the bone is 

 practically touching the trunk. Lastly, from the 

 position of the great vessels and nerves it will be seen 

 that in the subcoracoid and subglenoid luxations the 

 head of the bone may press injuriously upon those 

 structures. Thus may result oedema of the limb and 

 severe pain or loss of muscular power. The artery 

 is usually saved by its greater elasticity ; but Berard 

 reports a case of displacement forwards where the 

 axillary artery was so compressed by the humeral 

 head as to induce gangrene of the limb. 



The close connection of the circumflex nerve with the 

 humerus renders it very liable to injury, especially in 

 the subglenoid and subspinous forms of dislocation. 



Special anatomy of cadi form. 1. Sub- 

 coracoid. The articular head of the humerus lies on 

 the anterior surface of the neck of the scapula, and the 

 anatomical neck rests on the anterior lip of the glenoid 

 fossa. The head is thus placed immediately below the 

 coracoid process, and is in front of, internal to, and 

 a little below, its normal site The great tubcrosity 



