chap, i.] THE SCALP. n 



pterygoid venous plexus, the pharyngeal plexus, and 

 the internal jugular vein. 



Then, again, many minute veins connect the veins 

 of the scalp with those of the diploe. Of the four 

 diploic veins, two (the frontal and anterior temporal) 

 enter into surface veins (the supraorbital and deep 

 temporal), and two (the posterior temporal and 

 occipital) enter into the lateral sinus. 



Lastly, there is the well-known communication 

 between the extra- and intra-cranial venous circulation 

 effected by the commencement of the facial vein at 

 the inner angle of the orbit. In this communication 

 the angular and supraorbital veins unite with the 

 superior ophthalmic vein, a tributary of the cavernous 

 sinus. 



Through these various channels, and through many 

 probably still less conspicuous, inflammatory processes 

 can spread from the surface to the interior of the skull. 

 Thus we find such affections as erysipelas of the scalp, 

 diffuse suppuration of the scalp, necrosis of the 

 cranial bones, and the like, leading by extension to 

 mischief within the diploe, to thrombosis of the 

 sinuses, and to inflammation of the meninges of the 

 brain. If there were no emissary veins, injuries and 

 diseases of the scalp and skull would lose half their 

 seriousness. Mischief may even spread from within 

 outwards along an emissary vein. Erichsen reports a 

 case where the lateral sinus was exposed in a com- 

 pound fracture. The aperture was plugged. Throm- 

 bosis and suppuration within the sinus followed, and 

 some of the pus, escaping through the mastoid vein, 

 led to an abscess in the neck. 



The scalp nerves, especially such as are branches 

 of the fifth pair, are often the seat of neu- 

 ralgia. To relieve one form of this affection the 

 supraorbital nerve has been divided (neurotomy) at its 

 point of exit from the orbit, and a portion of the 



