BLOOD-VASCULAR SYSTEM OF THE LORICATI SI 
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 (Pls. I and II, figs. 1, 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. 
(6) Internal Jugular Veins (Pls. I and II, figs. 1, 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. 
1'This connecting sinus may be the same as the cross vessel connecting the 
two Bulbi ophthalmici described by Hyrtl (31, p. 236). 
Proc. Wash. Acad. Sci., June, 1905. 
