THE MIDDLE EAR 321 



the bone below the nerve of the pterygoid canal, from which it 

 may be distinguished by its lighter coloration. 



The sphenopalatine nerve is continued forward as the anterior 

 (major) palatine nerve, which passes through the pterygopalatine 

 canal to the posterior portion of the hard palate, but the spheno- 

 palatine nerve is also connected with the sphenopalatine ganglion. 

 Nasal rami pass to the mucous membrane of the nose, and the 

 nasopalatine nerve enters the nasal region, traversing the surface 

 of the septum and reaching the anterior portion of the palate 

 through the incisive foramina. 



The nerve of the pterygoid canal (n. canalis pterygoidei), or 

 Vidian nerve, is a slender cord which passes backward along the 

 orbital wall from the posterodorsal angle of the sphenopalatine 

 ganglion. It lies on the medial side of the sphenopalatine and 

 infraorbital nerves and on the lateral surface of the palatine bone. 

 Posteriorly, it enters the groove representing the pterygoid canal. 



This nerve is composed of two parts, separated posteriorly. 

 One of them, the deep petrosal nerve (n. petrosus profundus), is 

 connected with the sympathetic plexus of the internal carotid 

 artery, its fibres coming from the superior cervical ganglion. The 

 other, the great superficial petrosal nerve (n. petrosus super- 

 ficialis major), enters the skull at the foramen lacerum, passing 

 into the petrosal bone, in the interior of which it is connected with 

 the trunk of the facial. The nerve constitutes the motor root of 

 the sphenopalatine ganglion, the sensory root being that provided 

 by the sphenopalatine nerve. 



The sphenopalatine ganglion is one of several representing the 

 parasympathetic division of the autonomic system in the head, and 

 having motor and sensory roots from the cerebral nerves in addition 

 to autonomic connections. The series includes the ciliary gang- 

 lion, which lies on the optic nerve, the sphenopalatine ganglion, 

 the otic ganglia, associated with the mandibular nerve, and the 

 submaxillary ganglion, associated with the lingual nerve (Fig. 40) . 



13. Examination of the middle ear. 



By breaking away the ventrolateral portion of the tympanic 

 bulla and clearing the surface, the structures 6i the tympanic cavity 



