I40 THE SURGICAL ANATOMY OF THE HORSE 



where it lies on the serratus magnus muscle to which it is distributed, 

 its branches being given off to the muscle in a regular manner upwards 

 and downwards. The main nerve crosses the direction of the fibres of 

 the serratus magnus. 



Subcutaneous Thoracic Nerve 



This is a very long nerve, which arises from the eighth cervical and 

 the dorsal roots of the plexus in close relationship to the ulnar nerve. It 

 passes on to the deep surface of the large head of the triceps extensor 

 cubiti muscle, and subsequently follows the course of the spur vein which 

 is placed below the nerve, and with which it runs to the flank. It 

 terminates in the panniculus muscle. 



The branches given off by this nerve during its course are also 

 distributed to the panniculus, on the deep face of which they assist in 

 forming the network of nerve fibres to which the terminal filaments of 

 the intercostal nerves also contribute. 



One of its branches unites with a large perforating branch from the 

 second and third intercostal nerves, and the trunk thus formed winds 

 round the inferior border of the latissimus dorsi muscle across the back 

 of the limb, to be distributed to the panniculus muscle in the region of 

 the shoulder and arm. 



The Inferior Thoracic Nerves or Nerves to the Pectoral 



Muscles 



The anterior deep pectoral muscle is supplied by a nerve which 

 derives its fibres from the seventh and eighth cervical roots. 



The two divisions of the superficial pectoral derive their supply from 

 a nerve which comes from the two roots of the median nerve. This 

 nerve passes between the anterior and posterior deep pectoral muscles to 

 gain the superficial pectorals. 



