386 HEAD AND NECK 



breaks up into branches which accompany the anterior and middle cerebral 

 arteries. 



The internal carotid plexus communicates with the tympanic plexus by 

 means of superior and inferior carotico-tympanic branches given off in the 

 carotid canal, and with the spheno-palatine ganglion by the great deep 

 petrosal branch, which unites with the great superficial petrosal of the facial 

 nerve to form the nerve of the pterygoid canal (O.T. Vidian). It gives 

 branches also to the semilunar ganglion, the third, fourth, sixth and the 

 ophthalmic branch of the fifth nerve, and a branch which accompanies the 

 naso-ciliary nerve into the orbit and joins the ciliary ganglion. 



NERVUS MAXILLARIS. 



As the maxillary nerve passes anteriorly, from the semilunar 

 ganglion to the face, it traverses the foramen rotundum, the 

 upper part of the pterygo-palatine fossa, the pterygo-maxillary 

 fissure, the inferior orbital fissure and the infra-orbital canal. 

 The dissector should therefore proceed to expose the nerve 

 in these localities. 



Dissection. Remove the temporal muscle and the upper head of the 

 external pterygoid muscle, and, placing the saw upon the cut margin of the 

 skull at a point immediately above the external meatus, carry it obliquely 

 downwards and anteriorly through the squamous part of the temporal 

 bone and the great wing of the sphenoid, towards the medial end of the 

 superior orbital fissure. This saw-cut should enter the superior orbital 

 fissure immediately to the lateral side of the foramen rotundum. A 

 second saw -cut should then be made from the cut margin of the cranial 

 wall, immediately above the anterior margin of the great wing of the 

 sphenoid bone, downwards into the superior orbital fissure to meet the first 

 saw-cut. The wedge-shaped piece of bone included between these cuts 

 can now be removed. Additional space may be obtained, and the pterygo- 

 palatine fossa may be more fully opened up, by removing what remains of 

 the great wing of the sphenoid upon the lateral side of the foramen rotundum, 

 but the circumference of this aperture must be carefully preserved. Proceed, 

 in the next place, to open up the infra-orbital canal. In its posterior part 

 its upper wall is usually so thin that it can easily be removed by a pair 

 of dissecting forceps, but anteriorly it sinks deeply under the lower part of 

 the rim of the orbital opening, and here the chisel must be employed. 

 The maxillary nerve can now be defined and its branches displayed. 

 The infra -orbital artery and vein, which accompany the nerve in the 

 infra- orbital canal, will be exposed at the same time. 



Nervus Maxillaris. The maxillary nerve springs from the 

 semilunar ganglion within the cranial cavity (p. 330). It is 

 composed entirely of sensory fibres, and passes anteriorly, 

 outside the dura mater and in relation to the lower part of the 

 cavernous sinus, to the foramen rotundum through which it 

 enters the pterygo-palatine fossa. It crosses the upper part 

 of this fossa, curves laterally through the pterygo-maxillary 



