BLOOD-VASCULAR SYSTEM OF THE LORICATI 8 1 



The facialis-maxillaris vein is much larger than the corre- 

 sponding artery. It returns most of the venous blood from the 

 region of the maxilla ; while it is the orbito-nasal artery, which 

 furnishes this region with most of its arterial supply. 



The external jugular vein (Pis. I and II, figs, i, 5 and 15 ; 

 Ex.J.V.) is in itself a rather short trunk. It follows along in 

 front of the truncus infra-orbitalis or truncus buccalis-maxillo 

 mandibularis and the external carotid artery in the posterior 

 part of the orbit ; passing over the hyomandibular bone it unites 

 with the orbito-nasal and internal jugular veins in front of the 

 prootic process. 



(3) Internal Jugular Veins (Pis. I and II, figs, i, 13 and 15 ; 

 In.J.V.). — What has been designated as the internal jugulars 

 return the venous blood from the eye, recti muscles, and the 

 brain. Each of these trunks might be said to have its source 

 from the rectus, ophthalmic, and iris veins (see fig. 15) and at 

 this point of union it also receives or sends off a large sinus-like 

 vessel,^ which extends caudo-mesad in the eye-muscle canal and 

 anastomoses in the median line with a corresponding sinus-like 

 vessel from the opposite internal jugular vein. This horse-shoe 

 shaped sinus incloses the encephalic artery and receives a pos- 

 terior branch from each of the external recti muscles. The 

 main internal jugular vein becomes greatly reduced in caliber 

 in passing through what might be called the internal jugular 

 foramen (a foramen between the alisphenoid, prootic, and para- 

 sphenoid process, through which pass the internal jugular, the 

 iris artery, and the ciliary nerve). Emerging from this foramen 

 the internal jugular receives the encephalic vein, coming through 

 the cranium through the small encephalic vein foramen (the 

 most cephalic of the 3 foramina in the prootic, through which 

 the encephalic vein and ciliary nerve pass). In front of the 

 prootic process the internal jugular unites with the external 

 jugular at an angle of about 75°. Coming in between these 2 

 trunks is the orbito-nasal vein, which might almost be said to 

 unite with the internal jugular before it joins the external 

 jugular. 



'This connecting sinus may be the same as the cross vessel connecting the 

 two Bulbi ophthalmic! described by Hyrtl (31, p. 236). 

 Proc. Wash. Acad. Sci., June, 1905. 



