332 HEAD AND NECK 



of dura mater, and enters the middle cranial fossa at the root 

 of the posterior clinoid process ; there it bends at right angles, 

 and passes anteriorly to the lower root of the small wing of 

 the sphenoid, where it turns abruptly upwards and pierces 

 the inner layer of the dura mater, immediately posterior to 

 the entrance of the optic nerve into the optic foramen, and 

 on the medial side of the anterior clinoid process. It was 

 severed at this point during the removal of the brain ; but it 

 will be afterwards seen to end on the basal aspect of the 

 brain, at the commencement of the fissura lateralis (O.T. Sylvian 

 fissure), by dividing into the anterior and middle cerebral 

 arteries. Throughout its whole course it is surrounded by 

 sympathetic filaments, and soon after its entrance into the 

 cranium the abducent nerve crosses its lateral side. 



The intracranial portion of the internal carotid artery gives 

 off the following branches : 



1. Branches to the hypophysis, "I These are minute twigs 



2. Branches to the semilunar ganglion, which arise in the 



3. Branches to the dura mater, J cavernous sinus. 



4. Ophthalmic, ^ 



5. Posterior communicating, I These will be studied at a later 



6. Anterior cerebral, \ terminal j stage. 



7. Middle cerebral, / branches. J 



8. Choroidal. 



Plexus Caroticus Interims. The sympathetic filaments 

 which form this plexus can be satisfactorily dissected only in 

 a subject which has not been injected ; and even then, the 

 dissection is an exceedingly difficult one. The internal carotid 

 plexus is placed in the cavernous sinus and is chiefly massed 

 upon the lower and medial aspect of the internal carotid 

 artery, at the point where it makes its bend upwards. It 

 supplies filaments to the hypophysis, to the third and fourth 

 nerves, and to the ophthalmic division of the trigeminal nerve, 

 and gives the sympathetic root to the ciliary ganglion (O.T. 

 lenticular ganglion). 



Nervus Petrosus Superficialis Major. This small nerve, 

 along with a small arterial twig from the middle meningeal 

 artery, can readily be exposed in the groove on the anterior 

 face of the petrous bone which leads from the hiatus canalis 

 facialis to the foramen lacerum. It is placed under the semilunar 

 ganglion, which must therefore be turned antero-laterally. 

 In the canalis facialis it joins the ganglion geniculi of the 

 facial nerve. When traced in the opposite direction, it will 



