88 ALLEN 
sends off, or receives, a cross vessel from the corresponding 
vein on the opposite side. This cross vessel receives a branch, 
coming caudad along the dorsal surface of the oblongata. 
Whether it returns any of the venous blood from the cerebellum 
I was unable to determine. In the neighborhood of the origin 
of the vagus portion of the ramus lateralis accessorius from the 
dorsal root of the vagus, the posterior encephalic vein re- 
ceives an anterior branch or odlongata vein (Pl. Ill, fig. 24; 
Obl1.V.), which has its source from the side of the oblongata 
directly behind the roots of trigemino-facial complex, and 
shortly receives a branch from the posterior ampulla, then run- 
ning along the side of the oblongata, passes beneath the IX and 
X nerves and finally terminates by emptying into the posterior 
encephalic vein. Following along the dorsal root of the vagus 
nerve the posterior encephalic vein leaves the brain case 
through the vagus foramen in the exoccipital, but before leav- 
ing the skull the large myelonal vein is received from the rear. 
This vessel (Pl. III, figs. 23 to 25; My.V.) arises on the dorsal 
surface of the myel as far back as the 9th pair of spinal nerves. 
After running along on the dorsal surface of the myel fora 
short distance it separates into a right and a left myelonal vein. 
Each of these vessels runs along the lateral surface of the myel, 
passing between the dorsal and ventral roots of the spinal 
nerves, finally terminating by emptying into the posterior en- 
cephalic vein. Along its cephalic course the myelonal vein 
receives numerous vessels from the myel, and sends across 
dorsal connecting branches, which unite with the correspond- 
ing vein on the opposite side. Although the myelonal vein 
empties into the posterior encephalic vein, still, not all of its 
blood reaches the jugular through that vessel, but some of it is 
carried off by the first 3 sfzzal vezns (Pls. II and III, figs. 
16 and 24; Sp.V.). These vessels pass out with each alter- 
nate pair of spinal nerves, and emptying into the neural veins, 
which in the case of these anterior veins penetrate the dorsal sur- 
face of the head kidney, and here break up into very small 
veins, which again become collected into vessels that empty 
into the jugular vein. The posterior encephalic vein is simply 
a modified spinal vein, which after leaving the skull through 
