LATERAL PART OF MIDDLE CRANIAL FOSSA 241 



brain, at the commencement of the lateral fissure (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, \ 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, These win be studied at a Uter 



6. Anterior cerebral, \ terminal V st 



7. Middle cerebral, / branches, j 



8. Chorioidal. J 



Plexus Caroticus Interims. The sympathetic filaments 

 which form the internal carotid 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 

 massed chiefly 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, to the ophthalmic division of the trigeminal nerve and 

 to the semilunar ganglion, and gives the sympathetic root to 

 the ciliary ganglion (O.T. lenticular ganglion). 



Nervus Petrosus Superficialis Major. The greater super- 

 ficial petrosal 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 for- 

 wards and laterally. In the canalis facialis it joins the ganglion 

 geniculi of the facial nerve. When traced in the opposite 

 direction, it will be found to enter the foramen lacerum, where 

 it joins the deep petrosal nerve from the carotid plexus. The 

 trunk formed by the union of these two filaments is the nerve 

 of the pterygoid canal (O.T. Vidian nerve). 



. Nervus Petrosus Superficialis Minor. The lesser superficial petrosal 

 nerve appears upon the anterior face of the petrous bone, through an 

 aperture which is placed immediately lateral to the hiatus canalis facialis. 

 It leaves the cranial cavity by passing downwards between the great wing 

 of the sphenoid and the petrous part of the temporal bone, or through the 

 canaliculus innominatus or through the foramen ovale, to reach the otic 

 VOL. Ill 16 



