The; Head and Neck. 169 



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inferior). , This vessel passes upward and forward on the 

 medial wall of the orbit, giving branches to the eye muscles. 

 It divides into two branches, the frontal artery, which leaves 

 the orbit through the anterior foramen of the supraorbital 

 process, and the lacrimal artery, which passes through the 

 corresponding posterior foramen. The ethmoidal artery, a 

 small branch of the frontal, passes through the minute 

 ethmoidal foramen of the orbital portion of the frontal into the 

 nasal cavity. 



The internal maxillary artery passes forward along the ventral 

 boundary of the orbit, and at the opening of the infraorbital 

 canal gives off a branch, the pterygopalatine artery, con- 

 tinuing as the infraorbital artery. A small branch, the 

 superior dental artery (a. dentalis superior) is given off 

 laterally to the alveoli of the upper teeth. 



The infraorbital artery (a. infraorbitalis) passes through the 

 infraorbital canal to the face. 



The pterygopalatine artery (a. pterygopalatina) divides almost 

 immediately into the anterior palatine artery, which traverses 

 the pterygopalatine canal to the mucous membrane of the 

 hard palate, and the sphenopalatine artery, which enters the 

 nasal cavity by the sphenopalatine foramen. 



(b) The divisions of the third cranial, or oculomotor nerve, supply 

 the eye muscles, with the exception of the obliquus superior 

 and the rectus lateralis. 



This nerve enters the orbit from the superior orbital fissure in 

 company with certain parts of the trigeminal (e, f). The small 

 nerves passing through the middle and posterior sphenoidal formina 

 of the pterygoid process are the pterygobuccinator and masseterico- 

 temporal nerves, branches of the mandibular, passing to the muscles • 

 of mastication. 



(c) The fourth cranial, or trochlear nerve (n. trochlearis), is dis- 

 tributed to the obliquus superior muscle. 



(d) The sixth cranial, or abducent nerve (n. abducens), is dis- 

 tributed to the rectus lateralis. 



(e) The ophthalmic nerve (n. ophthalmicus), the first division of 

 the fifth cranial, or trigeminal nerve (n. trigeminus), accom- 

 panies the inferior ophthalmic artery on the medial wall of 

 the orbit. It gives off a lacrimal nerve, which passes upward 

 through the posterior foramen of the supraorbital process, 

 and then passing forward a short distance divides in two parts. 

 One of these, the frontal nerve, leaves the orbit through the 

 anterior supraorbital foramen, while the other, the naso- 

 ciliary nerve, is partly distributed to the anterior portion of 

 the orbit, and is connected with the minute ciliary ganglion 

 lying on the optic nerve, forming its sensory root. Its chief 

 portion leaves the orbit through the ethmoidal foramen of 

 the orbital portion of the frontal bone as the ethmoidal nerve 



