146 HEAD AND NECK 



terminations, but the nervus cutaneus colli must be traced only to the 

 point where it crosses either superficial or deep to the external jugular vein. 

 It eventually divides into upper and lower terminal branches, which will be 

 seen when the anterior triangle is dissected. 



Nervus Occipitalis Minor. The small occipital is a sensory 

 branch of the second cervical nerve. It emerges from under 

 cover of the sterno-mastoid, and ascends for a short distance 

 along its posterior border, then it passes to the superficial 

 surface of the muscle, pierces the deep fascia, and divides 

 into occipital, mastoid, and auricular branches. The occi- 

 pital and mastoid branches supply the skin in the regions 

 indicated by their names. The auricular is distributed to the 

 skin of the upper third of the cranial surface of the auricle. 



Nervus Auricularis Magnus. This consists of cutaneous 

 filaments derived from the second and third cervical nerves. 

 After turning round the posterior border of the sterno-mastoid 

 it runs upwards and anteriorly, towards the angle of the 

 mandible, in the deep fascia on the superficial surface of 

 the sterno-mastoid, and breaks up into three sets of terminal 

 branches, mastoid, auricular, and facial. The mastoid branches 

 go to the skin of the mastoid region. The auricular branches 

 supply the skin of the lower two-thirds of the cranial surface 

 and the lower third of the lateral surface of the auricle. The 

 facial branches, which have already been seen, ramify in the 

 posterior part of the face, in the parotid and masseteric regions. 

 Some of the filaments enter the substance of the parotid. 



Dissection. The accessory nerve, previously found at the junction of 

 the upper third with the lower two- thirds of the posterior border of the 

 sterno-mastoid, must now be traced downwards and posteriorly, through 

 the triangle, to the point where it disappears under cover of the trapezius, 

 at the junction of the upper two-thirds with the lower third of the anterior 

 border of that muscle. As the nerve is cleaned, attempt to secure twigs 

 from the third and fourth cervical nerves which communicate with it in 

 the posterior triangle. 



Turn next to the posterior belly of the omo-hyoid muscle, which 

 crosses the lower part of the triangle. Note that it divides the triangle 

 into a large upper or occipital portion, and a small lower or subclavian 

 portion. Cut through the fascia on the surface of the muscle, parallel with 

 the muscle fibres, and turn it upwards and downwards ; then turn the 

 upper border of the muscle laterally and find the nerve from the ansa 

 hypoglossi, which emerges from under cover of the sterno-mastoid and 

 enters the deep surface of the omo-hyoid to supply it. 



Take away the remains of the superficial layer of deep fascia, and the 

 areolar tissue beneath it from the upper part of the triangle. Whilst 

 removing the latter note a number of lymph glands which lie embedded 

 in it along the posterior border of the sterno-mastoid, superficial to the 

 stems and branches of the cervical nerves. At the apex of the triangle 

 look for the occipital artery, which either emerges between the adjacent 



