350 HEAD AND NECK 



The action of the former muscle is checked through an 

 intimate connection with the levator palpebrae superioris in 

 the anterior part of the orbit ; the action of the inferior rectus 

 is checked through a connection with the suspensory ligament. 



Dissection. In order that the zygomatic branch of the maxillary 

 division of the trigeminal nerve may be displayed in its course through the 

 orbit, the orbital contents must be removed. The nerve will then be 

 found in the midst of a little soft fat in the angle between the floor and 

 lateral wall of the orbit. 



Nervus Zygomaticus (O.T. Temporo-Malar). This small 

 nerve arises, in the infra-temporal fossa, 'from the maxillary 

 division of the trigeminal nerve. It enters the orbit by 

 passing through the inferior orbital fissure and almost 

 immediately divides into two terminal branches the 

 zygomatico-temporal and the zygomatico-facial. 



Ramus Zygomaticotemporalis. This branch runs antero- 

 superiorly upon the lateral wall of the orbit, under cover of the 

 periosteum, and, after receiving a communicating twig from 

 the lacrimal nerve, it enters the zygomatico - orbital canal 

 of the zygomatic bone. This conducts it to the anterior part 

 of the temporal region, where it has been examined already 

 (pp. 15 5 and 156). 



Ramus Zygomaticofacialis. The zygomatico-facial branch 

 also enters a zygomatico-orbital canal, and is finally con- 

 ducted to the face by the zygomatico - facial canal which 

 traverses the zygomatic bone (p. 127). 



PREVERTEBRAL REGION. 



The following are the structures to be displayed in this 

 dissection : 



Prevertebral muscles. 

 Intertransverse muscles. 

 Cervical nerves. 

 Vertebral artery. 



Vertebral vein. 



Vertebral and cranio-vertebral 

 articulations. 



Dissection. To separate the anterior part of the head with the pharynx 

 from the posterior part and the vertebral column a somewhat complicated 

 dissection is necessary. Place the head upside down, so that the cut margin 

 of the skull rests upon the table ; divide the common carotid artery, the 

 internal jugular vein, the vagus nerve, and the sympathetic trunk, on 

 each side, at the level of the neck of the first rib ; pull the trachea 

 and oesophagus, together with the great blood vessels and nerves, away 

 from the anterior surface of the vertebral column. The separation must 



