144 THE SURGICAL ANATOMY OF THE HORSE 



the fossa? on the dorsum of the scapula. The bulk of their bellies being 

 reduced, the length of their longitudinal axes becomes apparently increased, 

 with the result that there is still greater relaxation of the tendons which 

 play the part of retaining structures on the outer side ot the joint and as 

 a consequence the " slipping out " of the head of the humerus becomes 

 still more pronounced. Another feature of the disease now is the 

 greater prominence into which the spine of the scapula is brought 

 owing to the atrophy of the muscles which lie on either side of it. 



Prognosis should be guarded, since unsuccessful results frequently 

 follow treatment. Very little can be done to restore the injured nerve to 

 its pristine condition. Upon the first appearance of lameness, however, 

 the muscles should be massaged, and a counter-irritant applied to the 

 parts with friction, to endeavour to maintain the bulk of the muscles and 

 arrest atrophy. 



Subcutaneous injections of veratrin and oil of turpentine are also 

 recommended. 



THE MUSCULO-SPIRAL (OR RADIAL) NERVE 



During the course of dissection of the brachial plexus this nerve is 

 recognised without much difficulty by the fact that it is much the 

 thickest of the nerves given off by the plexus. Its fibres are derived 

 for the greater part from the dorsal roots of the plexus, but it also 

 receives slender contributions from the seventh and eighth cervical 

 roots. 



Leaving the plexus, the nerve at first lies on the deep face of the sub- 

 scapularis muscle, along which it runs in a direction which is downwards 

 and backwards, being here placed behind the ulnar nerve, which 

 separates it from the median nerve and its accompanying vessels. It 

 next crosses the long branch of the subscapular artery and passes on to 

 the surface of the teres major muscle. Crossing tlie artery to the 

 latissimus dorsi muscle, it continues its downward course parallel to the 



