io88 A MANUAL OF ANATOMY 



already enumerated ; (2) the muscular compartment, which is situ- 

 ated between the anterior or superficial layer and the pretracheal 

 layer, and contains the depressor muscles of the hyoid bone ; (3) the 

 visceral compartment, which lies between the pretracheal and pre- 

 vertebral layers, and contains the larynx, trachea, thyroid body, 

 pharynx, oesophagus, and carotid sheath, the retro -pharyngeal 

 space being in the subdivision of this compartment behind the 

 bucco-pharyngeal fascia ; and (4) the vertebral compartment, which 

 lies between the prevertebral layer and the attachment of the fascia 

 to the ligamentum nuchae posteriorly, and contains the vertebral 

 column, spinal cord, and prevertebral and postvertebral muscles. 



The suprasternal and muscular compartments are shut off from 

 the thoracic cavity. The visceral compartment, in front of the 

 trachea, is continuous with the superior mediastinum of the thorax, 

 and behind the oesophagus it, along with the retro-pharyngeal 

 space, is continuous with the posterior mediastinum. 



Parotid Process of the Deep Cervical Fascia. — ^This process is 

 given off a little below the angle of the inferior maxilla, and it 

 passes upwards on the deep surface of the parotid gland to the 

 skull. Along with the parotid fascia superficial to the gland it 

 forms a dense sheath which closely invests the glandular substance. 

 The parotid process furnishes sheaths to the posterior belly qf the 

 digastric, styloid, and pterygoid muscles, and it also gives an 

 investment to the superficial part of the submaxillary gland. Con- 

 nected with the parotid process there are several bands, usually 

 called ligaments, which are as follows : (i) spheno- mandibular ; 

 (2) stylo -mandibular ; (3) pterygo-mandibular ; and (4) pterygo- 

 spinous. 



The spheno-mandibular ligament will be described in connection 

 with the temporo-mandibular joint, of which it ranks as the internal 

 lateral ligament. 



The stylo-mandibular ligament extends from the styloid process 

 of the temporal bone, near its tip, to the angle and adjacent part of 

 the posterior border of the ramus of the inferior maxilla, where it is 

 placed between the masseter and internal pterygoid muscles. 



The pterygo-mandibular ligament is a narrow band which extends 

 from the hamular process of the internal pterygoid plate of the 

 sphenoid bone to the posterior extremity of the mylo-hyoid ridge 

 of the inferior maxilla, close to the last molar alveolus. Anteriorly 

 it gives origin to fibres of the buccinator muscle, and posteriorly 

 to fibres of the superior constrictor muscle of the pharynx. 



The pterygo-spinous ligament is a narrow band which extends 

 from a sharp spine on the posterior border of the external pterygoid 

 plate of the sphenoid bone, towards its upper part, to the spinous 

 process of the sphenoid. This ligament is liable to become 

 ossified. 



Sterno-cleido-mastoid — Origin. — ^The sternal head, which is 

 narrow and round, arises from the upper and outer part of the 

 anterior surface of the manubrium sterni. It is tendinous in front, 



