THE HEAD AND NECK. 131 



From what other sources does tJie dura receive its blood-supply ? 



The anterior meningeal arteries are in the anterior fossa of the skull. They 

 are derived from the ethmoidal branches of the ophthalmic artery, and from the 

 cavernous stage of the internal carotid. The small meningeal is a branch of the 

 first stage of the internal maxillary. It enters the cranium by the foramen ovale 

 with the third division of the fifth nerve. The posterior meningeal arteries 

 come from the vertebral, occipital, and ascending pharyngeal. 



Describe the cavernous stage of the internal carotid artery. 



It is in the cavernous sinus, but covered by the endothelial lining of the sinus. 

 (Fig. 86.) From the inner end of its petrosal stage the artery ascends to the pos- 

 terior clinoid process ; it then lies by the side of the body of the sphenoid, and 

 then gently curves upward between the middle and anterior clinoid processes, and, 

 lastly, curves backward and perforates the roof of the sinus. (Fig. 86.) On the 

 outer side of the artery is the sixth nerve. It is surrounded by sympathetic 

 nerves. 



In this stage the vessel gives off the following branches : 



1. Branches to the walls of the cavernous sinus. 



2. Branches to the Gasserian ganglion. 



3. Anterior meningeal branches to the dura. 



4. Branches to the pituitary body in the sella turcica. 

 Describe the petrosal stage of the internal carotid artery. 



It has in this stage two parts : An ascending part, in front of the tympanum 

 and internal ear ; a horizontal part, which you will see on turning the Gasserian 

 ganglion backward. On the artery you will see numerous sympathetic nerves, 

 the carotid sympathetic plexus, which are ascending branches of the superior 

 cervical ganglion. The carotid, Vidian, and tympanic are its branches. 



WJiat are Mcckel' s fascia, Meckel 's space, Meeker s cave, and the trigcminal 

 notc/i in the literature of the trigeminal nerve ? 



Meckel's fascia is the subdural connective tissue on and under the Gasserian 

 ganglion. Meckel's space is between the two layers of dura, external to the 

 cavernous sinus. Meckel's cave is a depression on the anterior surface of the 

 petrosa for the Gasserian ganglion. The trigeminal notch is an osteological term ; 

 it is a depression in the upper border of the petrosa, near the apex, in which the 

 fifth nerve rests before expansion into the Gasserian ganglion. This notch is 

 converted into the trigeminal foramen by the tentorium cerebelli. 



Describe the Gasserian ganglion. 



This ganglion lies in Meckel's cave, on the anterior surface of the petrosa. 

 It is simply an enlargement on the anterior or sensory root, as it is called, of the 

 fifth cranial nerve. Its posterior relations are the foramen lacerum medium, 

 the great petrosal nerve, and the horizontal part of the petrosal portion of the 

 internal carotid artery. Anterior to it is the dura mater. The ganglion gives 

 off or receives the following branches : 



1 . Filaments from the carotid plexus of the sympathetic. 



2. Nerves to the dura of the middle fossa and tentorium. 



3. The ophthalmic nerve to the orbit and nose. 



4. The superior maxillary nerve to the upper jaw. 



5. The inferior maxillary nerve to the mandibular region. 



Wliat is the function of the ganglion and the branches given off therefrom / 

 It confers the quality of common sensation on all parts to which it is dis- 

 tributed. Behind the ganglion lies a nerve that supplies the muscles of mastica- 

 tion. This is the so-called motor root of the fifth nerve. This nerve has nothing 

 to do with the ganglion. It leaves the base of the skull through the foramen 

 ovale with the inferior maxillary sensory part of the ganglion. (Fig. 53.) 



The tympanum or middle ear may be very satisfactorily dissected by the 



