142 THE SURGICAL ANATOMY OF THE HORSE 



Here the nerve crosses the subscapular artery, and subsequently accom- 

 panies the posterior circumflex artery round the back of the shoulder 

 joint. As it passes round the joint it gives off a slender filament to 

 the small scapulo-humeralis gracilis muscle. 



It then passes through the triangular space bounded by the teres 

 minor and the large and middle heads of the triceps extensor cubiti 

 muscle, and is now placed on the deep face of the deltoid, where it 

 splits up into a number of branches which supply the teres' minor, the 

 deltoid, and the mastoido-humeralis muscles, and the skin on the outer 

 aspect of the shoulder and for some distance down the front of 

 the arm. 



THE SUPRASCAPULAR NERVE 



The fibres of this nerve come from the sixth, seventh, and eighth 

 cervical divisions of the plexus. It is a very short nerve, but its 

 thickness is considerable. At first it runs for a short distance backwards 

 between the levator anguli scapula and the anterior deep pectoral 

 muscle, to place itself in company with the suprascapular artery. 



It passes into the interstice between the subscapularis and the supra- 

 spinatus muscles, and turns round the coracoid border of the scapula 

 between its middle and lower thirds to gain its dorsal surface. It gives 

 off a number of small filaments tor the supply of the supraspinatus 

 muscle, and passes into the infraspinous fossa by crossing the spine of 

 the scapula to supply the muscle which the fossa accommodates, namely, 

 the infraspinatus. 



PARALYSIS OF THE SUPRASCAPULAR NERVE 



Paralysis of the suprascapular nerve leads to a most peculiar lameness 

 to which the name " shoulder slip " is frequently given. 



During its course the nerve presents the greatest liability to injury 



