Thb Hbad and Neck. 157 



X. THE HEAD AND NECK. 



This dissection includes the various structures of the region, with the exception 

 of the cervical and occipital musculature and the central nervous system, which 

 are treated in the succeeding parts, and the special musculature of the ear, which 

 has been omitted. 



To begin the dissection, the skin, which has already been divided to 

 the mandibular symphysis and partly reflected, should be separated 

 from the underlying platysma along the side of the head, and reflected 

 until the surface is clear to a point near the dorsal median line of the 

 skull. The insertion of the platysma on the cheek, and that of its special 

 portion, the depressor conchae posterior, on the base of the ear, should 

 be noted. A second band of muscle, similar in its relation to the 

 platysma, arises from the lateral border of the mandible, immediately in 

 front of the masseter muscle, and is inserted into the base of the ear. 

 This is the depressor conchae (parotideoauricularis) anterior. 



In removing the skin of the upper and lower eyelids, two muscles, 

 the orbicularis oculi and the depressor palpebrae inferioris, may be 

 observed. The former is a somewhat circular band of fibres enclosing 

 both eyelids, the fibres lying directly on the skin, and being concen- 

 trated at the anterior and posterior angles. The latter is a very slender 

 muscle arising from the zygomatic arch and inserted into the skin of 

 the lower eyelid. The corresponding levator palpebrae superioris 

 arises from the orbital wall, and is here concealed by the projecting 

 supraorbital process. 



1. On the lateral surface of the head the following structures may 

 be made out without further dissection : 



(a) The masseter muscle. Origin: The zygomatic arch; 

 tendinous from its anterior angle. Insertion: Lateral sur- 

 face of the angle of the mandible, 



(b) The parotid gland (gl. parotis), a diffuse, white or brownish 

 gland lying immediately behind the angle of the mandible. 

 Its duct (d. parotideus) crosses the masseter and perforating 

 the mucous membrane of the cheek opens into the oral 

 cavity. 



(c) The chief part of the seventh cranial or facial nerve (n. 

 facialis) appears in the anterior portion of the parotid gland, 

 its branches crossing the masseter. They are distributed as 

 motor nerves to the cutaneous muscles of the face, including 

 the platysma. 



<d) The external maxillary artery (a. maxillaris externa) appears 

 at the ventral border of the mandible immediately in front 

 of the masseter. It passes upward to the anterior margin 

 of the eye, ending in the angular artery (a. angularis). Its 

 chief branches to the anterior portion of the face are: (1) 

 the submental artery (a. submentalis) to the chin; (2) the 



