SURGICAL ANATOMY OF THE NECK. 69 



great surgical importance, inasmuch as these aponeurotic 

 sheaths in a great measure control the course taken by 

 diffuse inflammation, collections of pus, blood, and 

 growths ; the latter frequently not appearing externally 

 in the neck until some while after they have extended 

 or sent processes along or amongst them. 



For convenience of examination and simplicity of 

 description it may be divided into two layers, a super- 

 ficial, and a deep. The superficial layer is usually traced 

 from behind, where it commences as a very thin lamina 

 attached to the spinous processes of the cervical verte- 

 brae, superior curved line of the occipital bone, and lig- 

 amentum nuchae ; and passing forwards, getting denser 

 as it proceeds, it incloses the trapezius, and, forming 

 sheaths for the posterior muscles of the neck, extends 

 over the posterior triangular space, and arriving at the 

 posterior border of the sterno-cleido-mastoid, forms a 

 sheath for it ; and part of it, which constitutes the an- 

 terior portion of this sheath, is attached to the lower 

 border of the body and angle of the lower jaw and 

 zygoma, after having covered in anteriorly the parotid 

 gland and masseter muscle ; below it is attached to the 

 anterior part of the clavicle "and manubrium sterni, and 

 is perforated by the external jugular vein and cutaneous 

 nerves. The deeper layer has an attachment to the 

 tubercles of the transverse processes of the cervical ver- 

 tebrae, and incloses the scaleni muscles, forming the 

 prevertebral aponeurosis, which sends processes over the 

 cords of the cervical and brachial plexuses and sub- 

 clavian vessels. The lax cellular tissue lying between 

 the prevertebral aponeurosis and the pharyngeal muscles 

 is the seat of retro-pharyngeal abscesses, which point 

 either into the pharynx or, guided by fascia, behind the 



