122 SURGICAL ANATOMY OP 



axillary artery can be felt, and which hollow may be 

 obliterated by the presence of axillary tumors or disloca- 

 tion of the humerus forwards. 



Externally, the roundness of the shoulder is formed 

 by the deltoid muscle, beneath which, and below the 

 overhanging process of the acromion, can be felt the 

 globular head of the humerus. This portion of the 

 bone is sometimes very large in proportion to the artic- 

 ulation, and might be mistaken for a displacement. In 

 any dislocation, however, the rotundity of the shoulder 

 gives place to a characteristic flattening; besides impair- 

 ment of the movements of the joint. Along the anterior 

 border of the deltoid is a groove between it and the 

 upper fibres of the pectoralis major, in which lie the 

 cephalic vein and a branch of the acromio-thoracic 

 artery. The skin of this region is very thick, and 

 glides easily over the underlying tissues, owing to the 

 presence of bursse, which are in some individuals more 

 or less developed, according to the use made of the 

 shoulder by their occupation or work thus, by carrying 

 a ladder or a hod of mortar, &c. 



To the upper border of the clavicle are seen attached, 

 along its sternal portion, the outer fibres of the sterno- 

 cleido-mastoid, and along its acromial portion the tra- 

 pezius. 



Below are the attachments of the pectoralis major 

 internally, and externally the deltoid. The clavicle can 

 be felt in its whole extent, owing to its subcutaneous 

 position, and from being so exposed is liable to fracture. 

 Again, its structure, its curves, which intensify the 

 shocks of indirect violence, and the want of support 

 posteriorly, all contribute towards the frequency of the 

 accident. 



