144 SURGICAL APPLIED ANATOMY. [Chap. ix. 



hand, instances are by no means uncommon where the 

 abscess or growth appears to ignore these membranes 

 and adopt a course of its own. 



The deep cervical fascia may be divided into (a) 

 the superficial layer, and (b) the deeper processes. 

 (a) The superficial layer forms a complete investment 

 for the neck, and covers in all the cervical structures, 

 excepting the platysma and some superficial veins and 

 nerves, with the completeness of a perfectly-fitting 

 cravat It commences behind at the spinous processes 

 of the vertebra, and, having invested the trapezius 

 muscle, starts, at the anterior border of that muscle, 

 as a single layer, to cross the posterior triangle. Ar- 

 riving at the posterior border of the sterno-mastoid 

 muscle, it splits, to enclose that structure, appearing 

 again as a single layer at the anterior border of the 

 muscle, from whence it passes to the middle line of 

 the neck to join the fascia of the opposite side, 

 entirely covering in on its way the anterior triangle. 

 The part that occupies the posterior triangle is 

 attached above to the mastoid process and superior 

 curved line of the occipital bone, and below to the 

 clavicle, so that the space is completely closed in by 

 the fascia in all parts, although, just above the 

 clavicle, it is pierced by the external jugular vein on 

 its way to the deeper trunks. Over the anterior 

 triangle, the fascia is attached above to the border of 

 the lower jaw. Behind that bone it passes over 

 the parotid gland to the zygoma, forming the parotid 

 fascia, while a deeper layer passes beneath the gland 

 (between it and its submaxillary colleague), to be 

 attached to points at the base of the skull. It is from 

 this deeper part that the stylo-maxillary ligament is 

 developed. In front the fascia is attached to the 

 hyoid bone, and just below the thyroid body it 

 divides into two layers again, one to be attached to 

 the front of the sternum, and the other to tlie back. 



