THE SUPERFICIAL CERVICAL REGION. 315 



Surgical Anatomy. It is essential to remember the direction of the fibres of the Platysma 

 in connection with the operation of bleeding from the external jugular vein ; for if the point 

 of the lancet is introduced in the direction of the muscular fibres, the orifice made will be 

 tilled up by the contraction of the muscle, and blood will not flow ; but if the incision is made 

 across the course of the fibres, they will retract and expose the orifice in the vein, and so allow 

 the flow of blood. 



Relations. By its external surface, with the integument, to which it is united 

 more closely below than above ; by its internal surface, with the Pectoralis 

 major and Deltoid, and with the clavicle. In the neck, with the external and 

 anterior jugular veins, the deep cervical fascia, the superficial branches of the 

 cervical plexus, the Sterno-mastoid, Sterno-hyoid, Omo-hyoid, and Digastric 

 muscles ; behind the Sterno-mastoid muscle it covers in the posterior triangle of 

 the neck. On tlieface it is in relation with the parotid gland, the facial artery 

 and vein, and the Masseter and Buccinator muscles. 



Action. The Platysma myoides produces a slight wrinkling of the surface of 

 the skin of the neck, in an oblique direction, when the entire muscle is brought 

 into action. Its anterior portion, the thickest part of the muscle, depresses the 

 lower jaw; it also serves to draw down the lower lip and angle of the mouth on 

 each side, being one of the chief agents in the expression of melancholy. 



The Deep cervical fascia lies under cover of the Platysma myoides muscle and 

 constitutes a complete investment for the neck. It also forms a sheath for the 

 carotid vessels, and, in addition, is prolonged deeply in the shape of certain proc- 

 esses or lamellae, which come into close relation with the structures situated in 

 front of the vertebral column. 



The investing portion of the fascia is attached behind to the ligamentum 

 nuchge and to the spine of the seventh cervical vertebra. Along this line it splits 

 to enclose the Trapezius muscle, at the anterior border of which the two enclosing 

 lamellae unite and form a strong membrane, which extends forward so as to roof 

 in the posterior triangle of the neck. Along the hinder edge of the Sterno-mastoid 

 this membrane again divides to enclose this muscle, at the anterior edge of which 

 it once more forms a single lamella, which roofs in the anterior triangle of the neck, 

 and, reaching forward to the middle line, is continuous with the corresponding 

 part from the opposite side of the neck. In the middle line of the neck it is 

 attached to the symphysis menti and body of the hyoid bone. 



Above, the fascia is attached to the superior curved line of the occiput, to the 

 mastoid process of the temporal, and to the whole length of the body of the jaw. 

 Opposite the angle of the jaw the fascia is very strong, and binds the anterior 

 edge of the Sterno-mastoid firmly to that bone. Between the jaw and the mastoid 

 process it ensheaths the parotid gland the layer which covers the gland extending 

 upward under the name of the parotid fascia to be fixed to the zygomatic arch. 

 From the layer which passes under the parotid a strong band, the stylo-mandibnhtr 

 ligament, reaches from the styloid process to the angle of the jaw. 



Below, the fascia is attached to the acromion process, the clavicle, and manu- 

 brium sterni. Some little distance above the last, however, it splits into two 

 layers, superficial and deep. The former is attached to the anterior border of the 

 manubrium, the latter to its posterior border and to the interclavicular ligament. 

 Between these two layers is a slit-like interval, the suprasternal space, or space of 

 Burns. It contains a small quantity of areolar tissue, and sometimes a lymphatic 

 gland; the lower portions of the anterior jugular veins and their transverse 

 connecting branch ; and also the sternal heads of the Sterno-mastoid muscles. 



The fascia which lines the deep aspect of the Sterno-mastoid gives off' certain 

 important processes, viz. : (1) A process to envelop the tendon of the Omo-hyoid, 

 and bind it down to the sternum and first costal cartilage. (2) A strong sheath, 

 the carotid sheath, for the large vessels of the neck, enclosed within which are the 

 carotid artery, internal jugular vein, the vagus, and descendens hypoglossi nerves. 

 (3) The prevertebral fascia, which extends inward behind the carotid vessels, 

 where it assists in forming their sheath, and passes in front of the prevertebral 

 muscles. It thus forms the posterior limit of a fibrous compartment which contains 



