60 LANDMARKS MEDICAL AND SURGICAL. 



deltoid, the upper part of the humerus. It distinctly moves 

 under the hand when the arm is rotated. It is not the head 

 of the bone which is felt, but the tuberosities, the greater 

 externally, the lesser in front. These tuberosities form the 

 convexity of the shoulder. When the arm is raised, this 

 convexity disappears ; there is a slight depression in its place. 

 The head of the bone can be felt by pressing the ringers high 

 up in the axilla. 



The absence of this prominence formed by the upper part 

 of the humerus under the deltoid, and the presence of a 

 prominence low in the hollow of the axilla, or in front, below 

 the coracoid process, or behind, on the back of the scapula, 

 bespeak dislocation of the head of the bone. 



In examining obscure injuries about the shoulder, it is 

 worth remembering that, in the normal relation of the bones, 

 and in every position, the great tuberosity faces in the direc- 

 tion of the external condyle. The head of the bone faces 

 very much in the direction of the internal condyle. 



It is worth remembering also that the upper epiphysis of 

 the humerus includes the tuberosities ; and that it does not 

 unite by bone to the shaft, till about the 2Oth year. 



By making deep pressure in front of the shoulder, when 

 the arm is pendent and supine, we can feel the bicipital 

 groove. It looks directly forwards, and runs in a line drawn 

 vertically downwards through the middle of the biceps to its 

 tendon at the elbow. We should be aware of this, lest it be 

 mistaken for a fracture. 



132. Coraco-acromial lig-ament. Under the anterior 

 fibres of the deltoid, we can distinctly feel the position and 

 extent of the coraco-acromial ligament. A knife, passed 

 vertically through the middle of it, goes at once into the 

 shoulder joint and strikes the bicipital groove with the tendon, 

 a point to be remembered in excision. 



In persons of an athletic build the triangular form and 

 beautiful structure of the deltoid become conspicuous when 

 the muscle is in action. The depression on the outer side 

 of the arm, indicating its insertion, is the place selected for 

 issues or setons. 



