28 THE SUPERIOR EXTREMITY 



of the pectoralis minor, find the lateral thoracic artery ; clean the 

 artery and the medial group of axillary lymph glands, which lie 

 along its course. 



At the junction of the posterior third and anterior two-thirds 

 of the medial wall of the axilla find the long thoracic nerve, which 

 supplies the serratus anterior and descends along its lateral 

 surface, from the apex to the base of the axilla. After the nerve 

 has been secured the serratus anterior must be cleaned. When 

 that has been done the dissector should clean the distal parts of 

 the large vessels and nerves and their branches and tributaries. 



With chain and hooks pull the axillary artery and the medial 

 cutaneous nerve of the forearm towards the arm and displace 

 the axillary vein in the opposite direction ; then find the ulnar 

 nerve which lies in the posterior part of the interval between the 

 artery and vein ; pull the ulnar nerve laterally, and behind the 

 artery find the large radial nerve (O.T. musculo -spiral). Pull it 

 medially and follow its lateral border upwards. At the lower 

 border of the subscapularis muscle on the lateral side of the 

 radial nerve secure the axillary nerve as it turns backwards into 

 the posterior wall of the axilla. Near the axillary nerve is the 

 large subscapular branch of the axillary artery accompanied by 

 the corresponding vein. The subscapular artery springs from 

 the medial side of the axillary artery. A short distance below its 

 origin it divides into two branches, the circumflex scapular and 

 the thoraco-dorsal. The circumflex scapular passes backwards 

 into the posterior wall of the axilla. The thoraco-dorsal artery 

 descends along the lower border of the subscapularis muscle to 

 the angle where the posterior wall joins the medial wall of the 

 axilla. Follow the artery downwards, taking care not to injure 

 the intercosto-brachial nerve and the posterior branches of the 

 lateral rami of the 3rd, 4th, and 5th intercostal nerves which cross 

 in front of it. Note the posterior group of axillary lymph glands 

 which lie along its course, and near its lower end secure the 

 thoraco-dorsal nerve, which crosses in front of the artery, on its 

 way to the latissimus dorsi, which it supplies. Return to the 

 division of the subscapular artery. Dissect in the angle between 

 its circumflex scapular and its thoraco-dorsal branches and 

 secure the second subscapular nerve, which supplies the teres 

 major muscle ; follow it to the muscle. 



Return to the radial nerve and find springing from its medial 

 border near the lower margin of the subscapularis the posterior 

 brachial cutaneous nerve, and branches to the long and medial 

 heads of the triceps muscle. Not uncommonly all those branches 

 are conjoined at their origin, and separate as they pass to their 

 destinations. The posterior brachial cutaneous nerve, on its 

 way to the middle of the posterior aspect of the arm, passes 

 behind the intercosto-brachial nerve. The nerve to the long 

 head of the triceps enters the proximal part of that muscle. 

 There are usually two branches to the medial head of the triceps ; 

 one enters the proximal part of the muscle, and the other, known 

 as the ulnar collateral, because it runs by the side of the ulnar 

 nerve, passes to the distal part. It will be traced to its termina- 

 tion at a later period. 



The anterior and posterior humeral circumflex branches of 

 the axillary artery will be found springing from the artery a 

 short distance distal to the subscapular branch, the former 



