THE EXTERNAL JUGULAR. 317 



from it ; and it likewise sends branches to the larynx and 

 pharynx. 



Before the internal jugular enters the foramen lacerum, it 

 suffers a partial dilatation, which is generally larger on one 

 side than the other.* This dilatation occupies the fossa at the 

 foramen lacerum. After passing through the aforesaid fora- 

 men, the internal jugular terminates in the lateral sinuses of 

 the dura mater.f These and the other sinuses within the 

 cavity of the cranium are important portions of the venous 

 system, which are interposed between the smaller branches, 

 spread upon the pia mater and the great trunks of the neck. 

 They will be described in the account of the brain. Into these 

 sinuses the very numerous veins of the pia mater, open, pro- 

 ceeding to the sinuses in a direction the reverse of that in which 

 the blood flows in those channels. 



These veins are divided very minutely on the pia mater 

 before they enter the substance of the brain. 



Into one of these sinuses, denominated the Cavernous, the 

 ophthalmic vein discharges its contents. This vein proceeds 

 from the anterior part of the sinus into the orbit of the eye 

 through the sphenoid fissure.J Its ramifications correspond 

 generally with those of the ophthalmic artery,<§. and some of 

 them pass out of the orbit to anastomose with the branches of 

 the facial vein. 



The superficial veins of the neck are variously arranged in 

 different persons. There is often one considerable vein, 



* When the veins of the neck are injected, it very often appears that a con- 

 siderable portion of the internal jugular is much larger on one side than the 

 other, as if it were affected with varicose distention. 



It also often appears that the general arrangement of the exterior vein is 

 different on the two sides of the head and neck. 



f It is asserted that the internal coat, or lining membrane of the internal 

 jugulars, is continued into the lateral sinuses, and extends throughout all the 

 sinuses of the dura mater ; so that the blood, during its passage through the 

 sinuses, does not come in contact with any membrane different from that of 

 the veins. 



I See the account of this fissure in vol. i. p. 132. 



<5> The Vasa Vorticosa of the choroides are one of the exceptions to this. 

 27* 



