SPINAL NERVES. 



753 



Superficial descending 



Deep 



Supra-clavicular. 



Supra-acromial. 



Communicating 



branches. 

 Muscular. 

 Phrenic. 



The superficialis colli (superficial cervical 

 nerve) takes its origin from the middle of the 

 plexus in company with, but anterior to the 

 great auricular, the anastomosing branches of 

 the second and third cervical nerves concurring 

 to form it. It emerges from behind the pos- 

 terior border of the sterno-mastoid about the 

 middle of the neck, and is directed horizontally 

 forwards and inwards, behind the external 

 jugular vein, and between the sterno-mastoid 

 and platysma, and at a variable point divides 

 into two branches, an ascending and descend- 

 ing, the former larger than the latter. 



The ascending branch almost immediately 

 divides into numerous filaments, some of which 

 supply the platysma myoides ; one or two 

 ascending along the external jugular vein. 

 The greater number are directed upwards and 

 forwards to the upper part of the platysma 

 and digastric muscle, communicate with the 

 deeper seated filaments given off' from the 

 portio dura, and becoming cutaneous, supply 

 the skin over the region of the sub-maxillary 

 gland, the chin (communicating with the sub- 

 mental nerve), and the lower part of the cheek ; 

 some filaments being directed to the median 

 line to communicate with the corresponding 

 nerve of the opposite side. 



The descending branch forms a loop, the 

 concavity of which looks upwards and inwards, 

 perforates the anterior part of the platysma, 

 a little above the middle of the neck, gives off 

 one or two twigs to accompany the anterior 

 jugular vein, and terminates in the skin about 

 the hyoid bone. 



The auricularis magnus(the auricular nerve) 

 arises in common with the trunk of the super- 

 ficial cervical from the anastomosing branches 

 between the second and third cervical. It 

 emerges from behind the posterior border of 

 the sterno-mastoid, above the superficial cer- 

 vical, and in front of the occipitalis minor. 

 It winds round the edge of the sterno-mastoid, 

 and is directed along it obliquely upwards 

 and inwards to the lower part of the parotid 

 gland on a level with the angle of the jaw, 

 reaches to the anterior border of this muscle, 

 and divides into a superficial and deep terminal 

 branch. It gives off before dividing several 

 filaments between the parotid gland and the 

 skin, and others which pass through the sub- 

 stance of the former to terminate in the skin 

 in the malar region, where it communicates 

 with the facial nerve. 



The superficial branch courses upwards in 

 the parotid fascia, and on a level with the 

 antitragus divides into several filaments, 

 which are distributed on the one hand to the 

 concave surface of the auricle, particularly the 

 concha ; and on the other, to the anterior 

 border of the helix, and the vertical groove in 

 front of it. 



The deep branch (anterior mastoid), having 



perforated the parotid gland, and crossed the 

 auricular branch of the facial, with which it 

 communicates, becomes placed behind the 

 auricle of the ear, ascends along the anterior 

 part of the mastoid process, communicates 

 with the occipitalis minor, and terminates by 

 supplying the skin at the back of the ear, some 

 filaments passing on to its upper border. 



The occipitalis minor (mastoid, external oc- 

 cipital) conies from the posterior part of the 

 cervical plexus, taking its origin from the 

 second cervical. It appears at the posterior 

 edge of the sterno-mastoid, behind and above 

 the great auricular. It passes upwards parallel 

 with the great occipital nerve directed by the 

 border of the splenius, which it occasionally 

 perforates, to the occipital region behind the 

 mastoid process ; communicates with the great 

 auricular externally, and with the great occipital 

 nerve internally, and ends by terminating in 

 the skin over the parietal bone. There occa- 

 sionally occurs a small accessory nerve, be- 

 tween the auricularis magnus and occipitalis 

 minor. This is directed along the posterior 

 border of the sterno-mastoid, and is distributed 

 to the skin over the mastoid process. 



The supra-clavicular and acromial nerves, 

 form the termination of the cervical plexus, 

 and exist as two primary trunks, which usu- 

 ally about the level of the posterior belly 

 of the omo-hyoid, divide and subdivide into 

 numerous branches, which traverse super- 

 ficially the posterior inferior triangle of the 

 neck, first passing behind the platysma, then 

 between it and the skin, The internal series 

 {sternal) are directed forwards and inwards, 

 over the lower part of the sterno-mastoid, 

 the inner third of the clavicle, and end 

 in the skin over the upper part of the 

 sternum, and upper and inner part of the pec- 

 toralis major. The middle filaments (mam' 

 mary) pass over the centre of the clavicle, 

 and are distributed to the skin of the pectoralis 

 major and the mammary gland, and commu- 

 nicate with branches of the intercostal nerves. 

 The posterior (clavicular} pass downwards 

 and outwards over the outer third of the cla- 

 vicle, and ramify in this skin over the anterior 

 and outer part of the deltoid. 



The acromial nerves are larger than the cla- 

 vicular, and are, ordinarily, two in number. 

 They pass obliquely outwards, downwards, 

 and backwards, over the lower part of the 

 superficial aspect of the trapezius, give some 

 filaments to this muscle, which communicate 

 with the spinal accessory nerve, and having 

 reached the acromion, divide into numerous 

 cutaneous branches, which ar.e lost in the 

 skin covering the spine of the scapula, and the 

 outer and back part of the deltoid. 



The communicating branches have been al- 

 ready partly described in the consideration of 

 the formation of the plexus ; and are formed 

 by different filaments, which are connected 

 with the trunk of the sympathetic, its upper 

 and middle cervical ganglion, as also with 

 the par vagum and lingual. The internal deep 

 branch is represented by the communicans 

 noni or internal descending cervical It takes 



3c 



