Chap, xii.] THE ARM. 203 



flattened on either side and unduly prominent in front 

 (biceps muscle). The outline of the biceps muscle is 

 distinct, and on either side of it is a groove. The 

 inner of the two grooves is by far the more con- 

 spicuous. It runs from the bend of the elbow to the 

 axilla, and indicates generally the position of the 

 basilic vein and brachial artery. The outer groove 

 is shallow, and ends above at the insertion of the 

 deltoid muscle. So far as it goes it marks the position 

 of the cephalic vein. 



The insertion of the deltoid can be well made out, 

 and is an important landmark. It indicates very 

 precisely the middle of the shaft of the humerus, is 

 on the same level with the insertion of the coraco- 

 brachialis muscle, and marks the upper limit of the 

 brachialis anticus. It corresponds also to the spot 

 where the cylindrical part of the humeral shaft joins 

 the prismatic portion. 



When the arm is extended and supinated, the 

 brachial artery corresponds to a line drawn along the 

 inner border of the biceps, from the outlet of the 

 axilla (at the junction of its middle and anterior 

 thirds) to the middle of the bend of the elbow. The 

 artery is superficial, and can be felt in its entire 

 extent. In its upper two-thirds it lies on the inner 

 aspect of the shaft of the humerus, and can be com- 

 pressed against the bone by pressure in a direction 

 outwards and slightly backwards. In its lower third 

 the humerus lies behind it, and compression, to be 

 effectual, should be directed backwards. 



The superior profunda artery and musculo-spiral 

 nerve cross the posterior surface of the humerus 

 obliquely at a spot on a level with the insertion of 

 the deltoid. 



The inferior profunda would be represented by a 

 line drawn from the inner side of the humeral shaft 

 at its middle to the back part of the internal condyle. 



