376 THE BRAIN 



BLOOD VESSELS OF THE BRAIN. 



The dissector should commence his study of the blood 

 vessels of the brain by an inspection of the veins of the brain. 

 He will readily find and easily follow some of the venous 

 blood channels, but he will have considerable difficulty in 

 tracing others from their commencements to their termina- 

 tions. Indeed, it may be that he will have to refer to specially 

 prepared specimens for confirmation of some of the points 

 about to be noted. 



The Veins of the Brain. The venous channels of the 

 brain include the venous blood sinuses of the dura mater, 

 and the veins which open into them. The venous sinuses 

 were noted when the dura mater was studied after the 

 removal of the brain (pp. 113, 114, 115). 



Veins of the Cerebral Hemispheres. The veins which 

 join the venous sinuses of the dura mater, and their tributaries 

 are still in situ. The majority of them lie in the subarachnoid 

 space on the surfaces of the hemisphere, but a few issue from 

 the interior of the brain. One of the latter, the great cerebral 

 vein, was seen when the upper parts of the brain were re- 

 moved from the cranium (p. 108). It emerges from beneath 

 the splenium of the corpus callosum, and runs upwards and 

 backwards, in the cistern of the great cerebral vein, to terminate 

 by joining the anterior end of the straight sinus in the tentorium 

 cerebelli (p. 107, Fig. 35). The cut end of it can still be 

 seen lying in the cistern, immediately posterior to the splenium 

 of the corpus callosum. 



Entering the great cerebral vein on each side is a tributary 

 called the basal vein ; it runs round the side of the 

 pedunculus cerebri, from the region of the anterior perforated 

 substance. The basal vein is formed, in the subarachnoid 

 space below the anterior perforated substance, by the union 

 of three veins, viz., (i) the anterior cerebral vein with (2) a vein 

 from the surface of the insula, called the deep middle cerebral 

 vein^ and (3) the anterior striate vein, which issues from the 

 substance of the brain. The anterior cerebral vein drains the 

 greater part of the medial surface of the hemisphere of the 

 same side and issues from the anterior part of the longitudinal 

 fissure, immediately anterior to the optic chiasma; then it 



