BLOOD VESSELS OF THE BRAIN 



383 



near the lower border of the pons, and it is rare to find the 

 vessels of the two sides of equal size. They converge, on 

 the anterior surface of the medulla oblongata, and unite 

 to form the commencement of the median vessel which 

 extends downwards on the ventral face of the spinal medulla. 

 The bulbar arteries are minute vessels which enter the 

 substance of the medulla oblongata ; they spring both from the 

 vertebral artery itself and also from its branches. 



Intermediate medial frontal 



Posterior medial frontal 



Anterior medial frontal 



Anterior 

 medial 

 frontal 

 branches 



Medial orbital 

 branches 

 Anterior cerebral artery 



, 



Calcarine branch Posterior cerebral artery 



Temporal branches 



FIG. 146. Medial and Tentorial Surfaces of the left Cerebral Hemisphere. 

 The district supplied by the anterior cerebral artery is tinted purple ; by 

 the middle cerebral artery, blue ; and by the posterior cerebral artery, 

 red. (Semi-diagrammatic.) 



Arteria Basilaris. The basilar artery runs from the lower 

 border to the upper border of the pons, occupying the median 

 groove of the pons and lying in the median part of the cisterna 

 pontis. It is formed, at the lower border of the pons, by the 

 union of the two vertebral arteries, and it divides, at the upper 

 border, into the two posterior cerebral arteries. It is sup- 

 ported anteriorly by the basilar portion of the occipital bone 

 and the dorsum sellae of the sphenoid (Fig. 38). 



The majority of the branches which spring from the basilar 

 artery arise from its sides and pass laterally from it. They 



are :- 



1. Pontine. 



2. Internal auditory. 



3. Anterior inferior cerebellar. 



4. Superior cerebellar. 



5. Posterior cerebral. 



