THE HEAD AND NECK 1087 



pneumogastric nerve, the latter being contained within the back 

 part of the septum, which separates the artery from the vein. 



The pretracheal or visceral lamina, which is at first intimately 

 connected with the anterior wall of the carotid sheath, passes for- 

 wards behind the depressor muscles of the hyoid bone, in which situa- 

 tion it splits to ensheathe 1 he thyroid body, trachea, and oesophagus, 

 and then it passes to the median line, where it is continuous with the 

 pretracheal lamina of the opposite side. The pretracheal lamina 

 is attached superiorly to the body of the hyoid bone, and inferiorly 

 it descends over the trachea and bloodvessels into the superior 

 mediastinum of the thorax, where it blends with the fibrous layer 

 of the pericardium. 



The prevertebral lamina, which is at first intimately connected 

 with the posterior wall of the carotid sheath, passes forwards behind 

 the pharynx and oesophagus, and in front of the prevertebral 

 muscles. It is known as the prevertebral fascia. At the middle line 

 it is continuous with the corresponding lamina of the opposite side ; 

 superiorly it is attached to the base of the skull ; and inferiorly it 

 descends over the longus colli muscle into the posterior medi- 

 astinum of the thorax. Along a line corresponding to the inner 

 wall of the carotid sheath the pretracheal lamina furnishes a 

 secondary lamina, called the bucco-pharyngeal fascia, which covers 

 the constrictor muscles of the pharynx and the buccinator muscle. 

 Between the bucco-pharyngeal and prevertebral fasciae there is an 

 interval, called the retro-pharyngeal space, which contains the 

 loosely arranged connective tissue uniting the two fasciae. This 

 space extends as high as the base of the skull, and inferiorly is con- 

 tinuous with the posterior mediastinum of the thorax. Another 

 process of the prevertebral fascia passes downwards and outwards 

 in front of the scalenus anticus muscle. Thereafter it invests the 

 third part of the subclavian artery and subclavian vein, together 

 with the nerve-trunks of the brachial plexus, and, passing behind 

 the clavicle, it becomes continuous with the axillary sheath, which 

 latter blends with the posterior aspect of the costo-coracoid mem- 

 brane. In the region of the subclavian triangle there is an inter- 

 fascial space between this process of the pretracheal fascia and the 

 superficial layer of the deep cervical fascia. This space extends 

 downwards behind the clavicle to the point where the axillary 

 sheath and costo-coracoid membrane join. It contains the pos- 

 terior belly of the omo-hyoid muscle, the suprascapular and trans- 

 verse cervical vessels, the lower part of the external jugular vein, 

 and the terminal portion of the anterior jugular vein. 



Interfascial Compartments. — It has been stated that the deep 

 cervical fascia reaches the median line of the neck anteriorly in 

 three layers, namely, anterior or superficial in (two divisions), pre- 

 tracheal, and prevertebral. It is therefore evident that there are 

 four interfascial compartments, as follows : (i) the suprasternal 

 space, or space of Burns, which is situated between the two divisions 

 of the anterior or superficial layer, and contains the structures 



