THE HEAD AND NECK. 49 



4. Wliat is the massctcric fascia ? 



The deep fascia covering the masseter muscle. It is of cervical derivation, 

 being, with the parotid fascia, the upward continuation of the first layer of the 

 deep cervical fascia. 



5. Name the structures on tlie masseter muscle . 



The parotid gland in part; the pes anserinus of the seventh nerve ; Stenson's 

 duct. In front of and under the anterior part of the muscle is some fat, called in 

 the child the sucking pad. 



6. Explain the relations and composition of the zygomatic arch. 



The arch is composed of a malar and a temporal portion. It has a superior 

 border into which is inserted the temporal fascia ; an outer surface that is 

 subcutaneous ; an inner surface and a lower border from which arises the 

 masseter muscle. Under the arch' are found the coracoid process of the 

 temporal bone, into which is inserted the temporal muscle ; the sigmoid notch, 

 through which pass the arteries and nerves to the masseter muscle. 



7. What structures lie on, and posterior to, the sterno-cleido-mastoid muscle ? 

 The muscle is ensheathed by the first layer of the deep cervical fascia. 



(Fig. 24.) On the muscle lie the auricularis magnus and the superficial cervical 

 nerves. The muscle is crossed by the external jugular vein. The spinal 

 accessory nerve and all the superficial branches of the cervical plexus pierce the 

 deep fascia at the posterior border of the muscle. These nerves are all in the 

 occipital triangle. 



8. Describe the superficial branches of the cervical plexus. (Fig. 22.) 



They are seven in number. The four ascending branches supply the neck 

 and side of the head with sensation. The three descending branches supply the 

 shoulder and upper third of the thorax. Their names are : 



1. Lesser occipital parallels the sterno-cleido-mastoid muscle. It supplies 

 the skin over the temporal muscle and the upper posterior part of the ear. 



2. The mastoid branch, or second small occipital, supplies the skin over the 

 insertion of the sterno-mastoid muscle into the mastoid process of the temporal 

 bone. 



3. The great auricular crosses the sterno-mastoid muscle to the ear, to which 

 and to the skin over the the parotid it is distributed. 



4. The superficial cervical nerve crosses horizontally the sterno-mastoid 

 muscle. It supplies with sensation the whole front of the neck. It passes be- 

 hind the external jugular vein. 



5. Suprasternal. This nerve supplies the skin over the origin of the sterno- 

 mastoid and over the manubrium sterni. 



6. The supraclavicular supplies the skin over the pectoralis major to the 

 nipple. It probably is this nerve that may account for the very diffuse pain over 

 the head, neck, and shoulders in sore nipples of nursing mothers. 



7. The supraacromial supplies the skin over the deltoid and clavicular por- 

 tion of the trapezius muscles. 



The Masseter Muscle (Fig. 25). Cut this muscle at its origin from the 

 malar process of the maxilla and the inner surface and lower border of the 

 zygoma. As you turn the same down, notice the nerve- and blood-supply 

 coming through the sigmoid notch. A little work with the forceps will remove 

 the fat and develop the insertion of the temporal muscle into the coracoid 

 process. Find the masseter inserted into the outer surface of the ramus of the 

 mandible. 



