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 (Pis. I, II, and III, figs, i, 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. 



Antcrio?' Cerebral Vein (PI. Ill, 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 larofer 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, i'nfundibulum, 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 Vein (PI. Ill, figs. 23 to 25 ; P.Cer.V.). 



— 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 (PI. Ill, figs. 23, 23^ and 25 ; Aud.V.) arises 

 from branches coming from the utriculus, anterior and external 

 ampullae. 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 



