84 ALLEN 
through what was designated as the internal jugular foramen, 
the internal jugular receives the encephalic vein shortly before 
uniting with the external jugular and orbito-nasal veins to form 
the jugular trunk. 
Encephalic Veins (P\s. I, II, and III, figs. 1, 15, 23, 24, and 
25; Enc.V.).—Each of these veins has its origin from 2 
branches, an anterior and a posterior cerebral vein. The for- 
mer returns the venous blood from the cerebrum, anterior sur- 
face of the optic lobes, optic and olfactory nerves; while the 
latter comes from the cerebellum, optic lobe, hypoaria, infundi- 
bulum, and the auditory region. 
Anterior Cerebral. Vem (P1. III, figs. 23 to 25 ;, A.Cer.V.). 
— Cephalad, this vein arises from a small vessel running caudad 
along the ventro-lateral surface of the olfactory nerve, and re- 
ceives a branch from the olfactory lobe and one from the optic 
nerve. About midway between the olfactory and the optic 
lobes it unites with a much larger vein from the cerebrum. This 
vessel arises from the inner parts of the cerebrum, and, passing 
laterad between the cerebrum and the optic nerve, considerably 
caudad of the corresponding artery, it unites with the small 
cephalic vein just described. The combined vessel continues 
caudad a short distance and when opposite the optic lobes re- 
ceives 2 or more branches coming from the anterior part of the 
hypoaria, infundibulum, hypophysis, and the anterior surface 
of the optic lobes. Then curving obliquely cephalad, the ante- 
rior cerebral vein proper crosses the III and IV nerves and the 
posterior cerebral artery to unite with the posterior cerebral 
vein in forming the encephalic trunk. 
Posterior Cerebral ‘Ven (PISIll, figs. 23\to125 ;) P.Cer Ve): 
— This vein has its source from 3 principal branches, namely: 
the mesencephalic, cerebellum and auditory veins, the 2 latter 
vessels uniting between the hypoaria and the optic lobes, im- 
mediately before the mesencephalic vessel is received. The 
auditory vein (P\. III, figs. 23, 23@ and 25; Aud.V.) arises 
from branches coming from the utriculus, anterior and external 
ampulla. The vein from the posterior ampulla empties into a 
branch of the posterior encephalic vein, and will be described 
under that vessel. Continuing cephalad for a short distance 
