DISSECTION OF THE HEAD AND NECK 207 



injury to the platysma, which lies in the superficial fascia. 

 Observe the superior rami of the cutaneous nerve of the front 

 of the neck (rami superiores N. cutanei colli), superficial to the 

 platysma. The superficial lymphatic channels can be well seen 

 only in especially injected specimens. (Vide Fig. 86.) 



Study the form, position, origin, insertion, innervation, and 

 action of the platysma. Is the muscle in general placed super- 

 ficial or deep as regards the panniculus adiposus ? Is the fat of 

 double chin premuscular, retromuscular, or both ? Note that the 

 platysma always moves with the skin of the neck. The loose 

 areolar tissue between the platysma and the superficial layer of 

 the fascia colli permits of free movement. What is the relation 

 of the anterior jugular and of the external vein to the platysma? 

 Why is the platysma called the muscle of fright? (Cf. Duchenne, 

 Mecanisme de la physionomie humaine, Figs. 61, 62, and 63.) 

 Why is it easier to pinch up a fold of skin vertically than trans- 

 versely in the neck! What effect would the platysma have on 

 the edges of a wound passing through the skin and muscles at 

 right angles to the course of its fibres? 



Structures between the Platysma and the Surface of the Fascia Colli. 

 Reflect the platysma from below upward, taking care not to 

 injure the subjacent nerves and veins. 



Veins. 

 External jugular (V. jugularis externa). 



(a) Posterior auricular (V. auricularis posterior). 



(b) Anterior jugular (V. jugularis anterior}. 



How would you draw a line on the surface of the neck correspond- 

 ing to the position of the external jugular vein? Observe the super- 

 ficial lymphatic glands (lympJioglandulae cervicales superficiales) 

 along the external jugular vein. How many are there? Whence do 

 they draw lymph? (Vide Figs. 86 and 93.) 



Nerves. 



Branches of the cervical plexus. 



(a) Lesser occipital nerve (N. occipitalis minor). 



(b) Great auricular nerve (N. auricularis magnus). 



(c) Cutaneous nerve of the front of the neck (N. cutaneus colli) (0. 



T. superficial cervical). 



(ca) Upper rami (rami superiores). 



(cb) Lower rami (rami inferiores). 



Is a cutaneous nerve of the back of the neck 

 cutaneus cervicis) present? 



(d) Supraclavicular nerves (Nn. supraclaviculares) . 



(da) Anterior (Nn. supraclaviculares anteriores) (0. T. supn 

 sternal). 



