224 HEAD AND NECK 



with those of the opposite side beneath the chin. The posterior fibres ascend 

 into the face, where they have already been followed to their connection 

 with the risorius and the orbicularis oris (p. 126). Cut through the platysma 

 along the anterior border of the sterno-mastoid and turn it upwards, dividing 

 the twigs of the cervical branch of the facial nerve which supply it. Secure the 

 two terminal branches of the nervus cutaneus colli (O.T. transverse cervical 

 nerve), crossing the middle of the sterno-mastoid, and the cervical branch 

 of the facial nerve below the angle of the mandible. Trace the nerves 

 anteriorly, and note the union between the upper branch of the nervus 

 cutaneus colli and the cervical branch of the facial. In the superficial 

 fascia of the submental region and the anterior part of the submaxillary 

 region secure the tributaries of the anterior jugular vein ; trace them down- 

 wards to the trunk of the vein and follow the trunk to the point where it 

 pierces the deep fascia ; then remove the superficial fascia and expose the 

 deep fascia of the anterior region. Note that the deep fascia extends in a 

 continuous layer from the mandible to the sternum and from the sterno- 

 mastoid of one side to that of the other side. Note, further, that it is 

 attached to the body and the great cornua of the hyoid bone. The latter 

 attachment separates the infra-hyoid muscles, which lie in the lower part of 

 the neck, from the supra-hyoid muscles, which are situated in the region of 

 the floor of the mouth. 



The dissectors will remember that in the course of the dissection of the 

 posterior triangle they met with several layers of the deep fascia. A similar 

 division into layers exists in the anterior region, and the opportunity should 

 be taken, whilst the fascia is still uninjured, to demonstrate certain of the 

 layers and the presence of the spaces between them. 



The Suprasternal Space. Make a transverse incision 

 through the deep fascia, immediately above the sternum, and 

 two vertical incisions, one along the anterior border of each 

 sterno-mastoid muscle. Carry the latter incisions upwards 

 for about one and a half inches, and turn the flap of fascia 

 marked out upwards. The space opened into by the reflection 

 of the first layer of deep fascia of the lower part of the neck 

 is the suprasternal space (Burns). Remove the areolar tissue 

 which fills it, find the lower parts of the anterior jugular 

 veins and the transverse anastomosis between them, and 

 expose the second layer of deep fascia, which forms the 

 posterior boundary of the space and covers and binds together 

 the infra-hyoid muscles of opposite sides. Pass the handle of 

 the scalpel downwards along the posterior wall of the space, 

 and note that it terminates, a short distance below the 

 upper border of the sternum, where the second layer of fascia 

 is attached to the posterior surface of the manubrium, 

 immediately above the origins of the infra-hyoid muscles. If 

 the handle of the knife is passed laterally along the posterior 

 wall of the space, it will pass deep to the sterno-mastoid into 

 the posterior triangle (see p. 145), and if it is pushed upwards 

 it will be stopped by the union of the first and second layers 



