BRACHIAL PLEXUS 



outer 



and inner. 



Three sub- 

 scapular : 



to subsca- 

 pularis, 



latissimus 

 dorsi, 



and teres 

 major. 



outer nerve crosses over the axillary artery, to the under- 

 surface of the great pectoral muscle in which it ends. On the 

 inner side of the vessel it communicates with the following branch. 



The in if r IK rre comes forwards between the artery and vein, and 

 after receiving the offset from the outer, ends in many branches to 

 the lander-surface of the pectoralis minor. Some twigs enter the 

 great pectoral muscle after passing either through the pectoralis 

 minor or above its border. 



The subscapular nerves are three in number, and supply the 

 muscles bounding the axilla behind : 



The upper nerve is the smallest, and enters the upper part of the 

 subscapularis muscle. 



The middle or long subscapular /u-rve accompanies the subscapular 

 artery along the posterior wall of the axilla, and supplies the 

 latissimus dorsi muscle (fig. 7). 



The lower subscapular nerve gives a branch to the lower part of 

 the subscapularis muscle, 

 and ends in the teres 

 major. 



Another branch of the 

 plexus, the posterior or 

 long thoracic nerve or 

 to the serratus, lies 

 on the inner side of the 

 axilla (fig. 6, 4 ). It arises 

 above the clavicle from 

 the fifth, sixth, and 

 seventh cervical nerves 

 fig. 8, pt), and descends 

 behind the axillary ves- 

 sels to reach the outer 

 surface of the serratus 

 magiius muscle. 



The LATISSIMUS DORSI 

 MUSCLE (fig. 7) may lie 

 examined as far as it 

 enters into the posterior 

 wall of the axilla. Arising from the back of the trunk (p. 7), 

 and crossing the lower angle of the scapula, the muscle ascends 

 to be inserted into the bottom of the bicipital groove, by a tendon insertion, 

 one inch and a half in width, in front of the teres major ; at 

 the lower border aponeurotic fibres connect the two, but a hursa 

 intervenes between them near the insertion (fig. 17, p. 44). 



Dissection. To lay bare the serratus magnus, the arm is to be 

 drawn from the trunk, so as to separate the scapula from the thorax. 

 The nerves of the brachial plexus should be included in a ligature 

 so as to hold them together, and cut through opposite the third rib ; 

 and the fat and connective tissue should be cleaned from the 

 muscular fibres. 



The SERRATUS MAGNUS MUSCLE (fig. 9) extends from the side Senatus 



magnus : 



FIG. 9. THE SERRATUS MAGNUS. 



Dissect inn 

 of the ser- 

 ratus. 



