The Head and Neck. 235 



X. THE HEAD AND NECK. 



This dissection includes the various structures of the region, with the excep- 

 tion 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 pl atyimia 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 platsyma, 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 de- 

 pressor conchae (parotideoauricularis) anterior. 



In removing the skin of the upper and. lower eyelids, two mus- 

 *les, the orbicularis oculi and. the depressor palpebrae infer- 

 ioris, may be observed. The former is a somewhat circular band 

 of fibres enclosing both eyelids, the fibres lying directly on the skin, 

 and being concentrated 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 )y The masseter muscle. Origin: The zygomatic arch* 

 ^ .tendinous from its anterior angle. Insertion: Lateral sur- 

 face of the angle of the mandible. 



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



\y 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, 



