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THE VASCULAR SYSTEMS 



puration in certain of the accessory sinuses of the nose, are frequently responsible for septic- 

 thrombosis of the cavernous sinuses, in exactly the same way as lateral sinus thrombosis is due 

 to septic disease in the mastoid process. Many deaths from meningitis, hitherto unaccounted 

 for, are in reality due to the spread of an infection from an ethmoidal or sphenoidal air cell to 

 the cavernous sinus, and thence to the meninges. It is obvious, therefore, that no case of chronic 

 nasal suppuration should be left untreated. 



The sphenoparietal sinuses may be regarded, together with the ophthalmic- 

 veins, as the commencement of the corresponding cavernous sinuses. Each of these 

 sinuses (sinus sphenoparietalis) is lodged in the dura on the under surface of the 

 lesser wing of the sphenoid bone. It takes origin from one of the middle meningeal 

 veins, usually receives blood from the diploe of the skull, passes inward, and ends 

 in the anterior part of the cavernous sinus. 



The ophthalmic veins are two in number, superior and inferior. 

 The superior ophthalmic vein (v. ophthalmica superior) (Fig. 506) begins as the 

 nasofrontal vein (v. nasofrontalis), which communicates with the angular vein at 

 .the inner angle of the orbit. It joins the angular vein with the cavernous sinus; 



it pursues the same course 

 as the ophthalmic artery, 

 and receives tributaries 

 corresponding to the 

 branches derived from 

 that vessel. Forming a 

 short single trunk, it 

 passes through the inner 

 extremity of the sphen- 

 oidal fissure, and termi- 

 nates in the cavernous 

 sinus. It anastomoses 

 with the inferior oph- 

 thalmic vein and receives 

 lacrimal, anterior and 

 -Opening of masioid posterior ethmoidal, and 

 muscular branches, and 

 veins of the eyelids and of 

 theeyeball(Vy. vorticosae). 

 The inferior ophthalmic 

 vein (v. ophthalmica in- 

 ferior) (Fig. 506) arise* 

 in the veins of the eyelids 

 and lacrimal sac, receives 

 the veins from the floor of 

 the orbit, and either passes out of the orbit through the sphenoidal fissure to join 

 the pterygoid plexus of veins, or else, passing backward through the sphenoidal 

 fissure, it enters the cavernous sinus, either by a separate opening, or, more fre- 

 quently, in common with the superior ophthalmic vein. It receives muscular 

 tributaries and veins of the eyeball, and anastomoses with the superior ophthal- 

 mic and the deep facial vein. 



The circular sinus (sinus circularis) (Figs. 505 and 507) is formed by two 

 transverse vessels, the anterior and posterior intracavernous sinuses (sinus inter- 

 cavernosus anterior and sinus intercavernosus posterior), which connect the two 

 cavernous sinuses; one passes in front and the other behind the pituitary body, 

 and thus they form with the cavernous sinuses a venous circle around that body. 

 The anterior one is usually the larger of the two, and one or other is occasionally 

 absent. 



' Torcular Herophili. 

 FIG. 507. The sinuses at the base of the skull. 



