THE HEAD, ANTERIOR. 43 



The Cavernous Sinus. Diags. I and 2. Fig. 10. 



Two, one on either side of the body of the sphenoid 

 bone. 



It extends from the inner extremity of the sphenoidal 

 fissure, where it receives (is really the continuation of) the 

 ophthalmic vein from the orbit, to the apex of the petrous 

 portion of the temporal bone, where it terminates in the 

 superior and inferior petrosal sinuses. 



Diag. 3. A DIAGRAM OF THE CAVERNOUS SINUS. (/. S. ff.) The diagram 

 shows the right sinus divided transversely and its cavity filled with fine interlacing 

 trabeculae. i, Ophthalmic division of the fifth cranial nerve. 2, Fourth cranial nerve. 

 3, Third cranial nerve. 4, Sixth cranial nerve. 5, Internal carotid artery. 



The cavernous sinuses are connected across the sphenoid 

 bone by the circular sinus. 



Upon the inner wall of the cavernous sinus is the inter- 

 nal carotid artery and the sixth nerve ; on the outer wall 

 the third,, fourth, and ophthalmic division of the fifth nerves ; 

 all these structures are separated from the blood in the 

 sinus by a covering of endothelium. 



