30 Anatomy Applied to Medicine and Surgery. 



other varieties. In the subspinous form, in addition to 

 the condition of the deltoid, supra-spinatus and biceps, 

 above described, the subseapularis is stretched Across the 

 empty glenoid fossa, the infra-spinatus is tense, so, too, 

 are the pectoralis major and the latissimus dorsi, ,but the 

 teres major and teres minor, however, are relaxed/ In 

 each form, then, the elbow is abducted, , but in the subcora- 

 coid variety, the head being in front of the joint, the elbow 

 is posterior to the midaxillary line, partly because of the 

 shape of the bony surface on which the head rests and 

 partly from the traction of the latissimus dorsi and the 

 posterior fibres of the deltoid. In the subspinous form, 

 the head being behind the joint, the elbow is anterior )to 

 the midaxillary line, due partly to the contour o*f the bony 

 surfaces in contact with one another, and partly to the 

 traction of the pectoralis major and the anterior fibres of 

 the deltoid ; whereas, in the sub glenoid, the elbow occupies 

 a midposition, i.e., about the midaxillary line. 3. Dugas' 

 sign. In a normal arm, if the elbow be placed on the side 

 of the chest, the hand can rest on the opposite shoulder. 

 When, however, dislocation occurs, this is impossible, and 

 may be explained as follows : The humerus represents a 

 straight line, and the thorax, a circle, and, therefore, since 

 the humerus touches the thorax at one point it cannot at 

 another, hence it is impossible for the elbow to touch the 

 chest wall, in dislocation, except from the application pf 

 considerable force. 4. If a straight edge be applied along 

 the outer aspect of the normal ,arm, it .lies about half an 

 inch outside of the acromion process, since the head of the 

 bone projects that much beyond the ( acromion. When, 

 however, a displacement occurs, the straight edge, not 

 resting on the 'head of the bone, will touch ,the acromion. 



To distinguish between a dislocation at the shoulder 

 joint and a fracture of the surgical neck of the scapula, 

 tihe following points will assist : 



