The Meninges of the Btain. 415 



The Cerebral Sinuses are formed by a separation 

 of the two layers of dura mater. These sinuses 

 convey the blood from the surface and the in- 

 terior of the brain itself to the outside of the skull. The 

 longitudinal, superior and inferior, the straight, the occi- 

 pital and the superior petrosal, converge to the internal 

 occipital protuberance and then pass, by means of the 

 lateral (especially the right one), to the jugular foramen, 

 where they meet with the inferior petrosal conveying the 

 blood from the cavernous, the circular, the transverse and 

 the spheno-parietal. The cerebral veins empty into these 

 sinuses, and, in the case of the superior longitudinal and 

 the posterior part of the lateral, these veins run for a 

 little distance in the walls of the sinuses and then open out 

 in a direction opposite to the current of blood in the sin- 

 uses. By this arrangement, and because of the presence 

 of trabeculse in the interior of the sinuses, the velocity of 

 the blood current is diminished and thus the circulation 

 of the blood within the cranium is equalised. 



Diseases of the Cerebral Sinuses. Communicating, 

 as the sinuses do, with the exterior, by means of emissary 

 veins, it follows that infective sinus thrombosis is by no 

 means uncommon (non-infective thrombosis may 

 occur in wasting diseases whereby the current of blood is 

 rendered very slow, so that coagulation results, as seen in 

 cholera infantum, marasmus, etc). The influence of the 

 emissary veins in the production of this serious condition 

 of infective sinus thrombosis is seen in such infections as 

 erysipelas, septic wounds, etc., involving the region of the 

 face, and, under these circumstances, the connection is by 

 means of the ophthalmic vein a tributary of the cavern- 

 ous sinus with the supra-orbital and facial veins. An- 

 other instance is where the nasal passages are involved. 

 In this case the disease spreads through the communica- 



