838 THE VASCULAR SYSTEM. | 
where they receive tributaries from the inner surface of the hemispheres, and they 
terminate in the superior longitudinal sinus. The anterior veins of this set are 
small and run transversely inwards, but the posterior are large and run obliquely 
forwards and inwards; the xy are embedded for some distance in the wall of the sinus, 
and their orifices are directed forwards, against the blood-stream. 
The inferior cerebral veins (vv. cerebri inferiores) lie on the lower and outer 
aspects of the cerebral hemispheres ; they run downwards and inwards, and terminate 
in the sinuses which he at the base of the skull—viz. the cavernous, the superior 
petrosal, and the lateral sinuses. One of these veins, the superficial Sylvian vein, 
runs along the posterior horizontal limb and stem of the fissure of Sylvius to the 
cavernous sinus; occasionally it is united by an anastomotic loop, known as the 
great anastomotic vein of Trolard, with the superior longitudinal sinus, and some- 
times by the posterior anastomotic vein with the lateral sinus. 
The anterior cerebral vein of each side lies in the great longitudinal fissure and 
accompanies the corresponding anterior cerebral artery ; it receives tributaries from 
the corpus callosum and the callosal convolution. Turning downwards round the 
genu of the corpus callosum, it reaches the base of the brain, and terminates in the 
basilar vein. 
The deep Sylvian vein lies deeply in the fissure of Sylvius; it anastomoses freely 
with the superficial Sylvian vein, receives tributaries from the Island of Reil and 
the adjacent opercula, and terminates in the basilar vein. 
The basilar vein commences at the anterior perforated space ; it is formed by the 
union of the anterior cerebral vein with the deep Sylvian vein and with the inferior 
striate vein. Passing backwards round the crus cerebri, it terminates in a vein — 
of Galen. Its tributaries are derived from the tuber cinereum, the corpus albicans, 
the posterior perforated space, the uncinate gyrus, the inferior cornu of the lateral 
ventricle, and the crus cerebri. 
Veins of the Mid-brain.—The veins of the mid-brain terminate for the most 
part in the veins of Galen. 
Cerebellar Veins.—These veins also are divisible into two groups, the super- 
ficial and the deep. The former are quite independent of and much more 
numerous than the arteries. They form two sets, the superior and the inferior. 
The superior superficial cerebellar veins (vy. cerebelli superiores) terminate in a 
single median or vermian efferent vessel and in several lateral efferents. The 
Superior vermian vein runs forwards and ends in the vena magna Galeni, and the 
lateral superior cerebellar veins terminate in the lateral sinuses or in the superior 
petrosal sinuses. 
The inferior superficial cerebellar veins (vy. cerebelli inferiores) also form a 
small vermian and numerous lateral efferents; the former runs backwards and 
joins either the straight sinus or one of the lateral sinuses, and the latter end in 
the inferior petrosal and occipital sinuses. 
The deep cerebellar veins issue from the substance of the cerebellum and 
terminate in the superficial veins. 
Veins of the Pons Varolii—tThe deep veins from the substance of the pons pass 
forwards to its anterior surface, where they become superficial, and, anastomosing 
together, form a plexus which is drained by superior and inferior efferent veins. 
The superior efferent veins join the basilar vein; the inferior efferent veins either 
unite with the cerebellar veins, or they open into the superior petrosal sinus. 
Veins of the Medulla Oblongata.— Deep veins of the bulb issue from its sub- 
stance and end in a superficial plexus. This plexus is drained by an anterior and _ 
a posterior median vein and by radicular veins. 1 
The anterior median vein is continuous below with the corresponding vein of the 
spinal cord ; it communicates above with the plexus on the surface of the pons. 
The saRtereS median vein is continuous below with the posterior median vein 
of the cord, from which it ascends to the lower end of the fourth ventricle, where 
it divides into two branches which join the inferior petrosal or basilar sinuses. 
The radicular veins issue from the lateral parts of the plexus and run with the 
roots of the last four cranial nerves; they end in the inferior petrosal and occipital 
sinuses. 
