SHOULDER, ARM, FOREARM, HAND. POSTERIOR PART. 361 



lip of the scapular spine and acromion, and into the posterior outer one-third 

 of the clavicle. (Fig. 252.) 



3. Describe the circumflex nerrc. 



It is a branch of the posterior cord of the brachial plexus. (Fig. 42.) It 

 passes through the circumflex quadrangular space, to the back of the shoulder. 

 It gives muscular branches to the deltoid and teres minor muscles, and cutaneous 

 branches to the skin covering the insertion of these muscles and articular 

 branches to the shoulder-joint. (Hilton's la\v.) 



Supra-spinatua Suprasca/mlar artery 



Posterior scapular artery | | Infra-spinatus 



Hhomboideus minor / 



Levator anguli scapulae 



Triceps, cut 



Deltoid, insertion 

 Deltoid 



Trapezius 

 Rhomboideus major 



Terea major muscles 



Deltoid muscle 

 / 

 Triceps 



Teres major, insertion 

 Dorsalis scapulae artery Posterior circumflex artery 



FIG. 254. THE DORSAL SCAPULAR ARTERY. 

 (From a dissection in the Museum of the Royal College of Surgeons.) 



4. Describe the suprascapular nerve. 



A branch of the upper trunk of the brachial plexus. (Fig. 42.) It passes 

 through the constant suprascapular foramen. It gives muscular branches to 

 (i) the supraspinatus, (2) the infraspinatus, and articular branches from each 

 muscular branch, to the shoulder-joint. (Hilton's law.) 



5. Describe the muscnlo-spiral nerve. 



It is a branch of the posterior cord of the brachial plexus. (Fig. 42.) It 

 may be found on the floor of the second triangular space. (Fig. 249.) It passes 

 between the two humeral heads of the triceps in the musculo-spiral groove of the 

 humerus. It lies between the brachialis anticus and brachio-radialis muscles in the 

 lower third of the arm. It gives muscular branches to the triceps and anconeus 

 24 



