BLOOD VESSELS OF THE BRAIN 



by the bifurcation of the basilar artery into the two posterior 

 cerebral vessels (Fig. 144). As a rule, the circulus arteriosus 

 is not symmetrical. One posterior communicating artery is 

 almost invariably larger than its fellow of the opposite side. 



Two systems of branches, both going to the cerebrum but 

 differing greatly in their mode of distribution, proceed from 

 the cerebral arteries. One system consists of very numerous, 



Optic nerve 



Internal carotid 

 artery 



Trigeminal nerve 

 Trochlear nerve 



Glosso-pharyn- 

 geal nerve 



Accessory nerve 



Section through 



the medulla 



oblongata 



Posterior 

 communicating 

 artery 



Oculo-motor nerv 

 Posterior cerebr 

 artery 

 Superior 

 cerebellar arte 

 Tentorium 



Basilar 

 artery 



Vertebral 

 artery 



Superior petrc 



sinus 



Transverse sinu< 



Transverse sinus 



Occipital sinus 



Straight sinus (divided) 



Superior sagittal sinus 



FIG. 145. Floor of the Cranium after the removal of the Brain and the 

 Tentorium Cerebelli. The blood vessels forming the Circulus Arteriosus 

 have been left in place. 



slender twigs, which, as a rule, come off in groups in certain 

 localities, and at once pierce the substance of the cerebrum 

 to gain its interior. It is the system of central or basal 

 branches. The other system is composed of branches which 

 ramify over the surface of the cerebrum, and it is termed the 

 system of cortical branches. The central parts of the brain, 

 including the basal ganglia, receive their blood supply from 



