856 THE NEBVE8. 



anastomoses by convergence. Those of the fifth and sixth pairs, uniting at the 

 anterior border of the scalenus with a branch of the brachial plexus, constitute the 

 diaphrngmatic {phrenic) nerve, which will be noticed hereafter. 



The superficial ramuscules gain the external surface of the mastoido- 

 humeralis by traversing its substance, or passing between its two portions. 

 Much more numerous and larger than the preceding, they are distributed — in 

 front — to the cervical panniculus ; behind, to the trapezius ; or below, to the 

 mastoido-humeralis and pectoralis anticus and transversus. Those passing to the 

 two last muscles are very long and voluminous ; they represent the acromial and 

 clavicular branches of the cervical plexus of Man. It may be remarked that the 

 posterior filaments generally communicate with the spinal accessory, while the 

 anterior ones, in meeting the cervical branch of the facial nerve on the jugular, 

 often give it some anastomosing fibres. 



Seventh. — An enormous branch comes from the interstice between the two 

 portions of the scalenus, to pass entirely into the brachial plexus. It usually 

 receives an anastomosing twig from the diaphragmatic filament furnished by the 

 sixth pair. 



Eighth. — This is thicker than the preceding, and comports itself like it. It 

 directly furnishes its anastomotic branch to the inferior cervical ganglion. 



Aeticle II. — DoESAL Nerve (17 Paies). 



These nerves, numbering seventeen pairs, comport themselves in an extremely 

 simple and almost identical manner ; so that their description is not nearly so 

 complicated as that of the nerves of the cervical region. 



Superior Branches. — They present two principal ramuscules for the spinal 

 muscles and the skin of the dorso-lumbar region. One ascends towards the summit 

 of the spinous processes of the dorsal vertebrae, by passing between the semi- 

 spinalis and longissimus dorsi ; the other is directed outwards, in traversing the 

 substance of the latter muscle. 



Inferior Branches. — These are more considerable in size than the pre- 

 ceding, and descend into the intercostal spaces, between the pleura and the 

 internal intercostal muscles, or even in the texture of these. With the exception 

 of the first, the arrangement of which is different, they all pass at first over the 

 head of the posterior rib to reach the convex border of the anterior one, and 

 follow it to the extremity of the intercostal space. 



There they terminate in the following manner : those of the sternal ribs 

 traverse the pectoral muscles, giving filaments to these, and are expended in the 

 skin of the subthoracic region. Those of the asternal ribs enter the abdominal 

 muscles, passing between the transversalis and rectus abdominis ; they also give 

 cutaneous filaments to the skin of the abdomen. 



Near their origin, the inferior branches communicate with the sympathetic, 

 for the most part, by several filaments. 



In their course they furnish numerous fine ramuscules to thf^ intercostal 

 muscles, and, in addition, give off — about the middle of their length — a very thick 

 division — the perforating intercostal hranch, which traverses the costal muscles 

 and descends beneath the panniculus carnosus, ramifying partly in that muscle 

 and partly in the skin. The most anterior perforating branches generally anas- 

 tomose with the subcutaneous thoracic branch of the brachial plexus. 



With regard to the first dorsal pair, its inferior branch enters the latter 

 plexus ; but it nevertheless furnishes an intercostal branch, always extremely 



