246 THE SALAMANDER 



(c) R. mesencephali superior (Gaupp, Frog). This branch passes 

 round between the optic lobes and the cerebellum. It supplies the 

 latter, and finally terminates within the chorioid plexus of the fourth 

 ventricle. 



((T) R. communicans continues the direction of the main stem 

 mesially, and anastomoses with the corresponding branch from the 

 other side. From the transverse vessel thus formed there arises, in 

 the middle line, the basilar artery. 



The Arteria hasilaris (a.b.) (Gaupp, Frog) arises by two or three 

 roots, which almost immediately fuse to form a median vessel cours- 

 ing along the mid-ventral line of the medulla oblongata, and giving 

 numerous fine branches to it on either side. The auditory artery is 

 given off just anterior to nerve V. 



The Arteria auditiva (Gaupp, Frog) passes into the auditory cap- 

 sule along with nerve VIII. 



The A. basilaris is continued right along the vertebral column, 

 where it is called the A. spinalis ventralis (Gaupp, Frog). It is 

 the artery of the spinal cord. 



B. Veins. It is not possible to give a connected account of veins 

 of the brain since they converge on more than one point. The follow- 

 ing description therefore commences at the anterior end of the brain 

 and works backwards. 



The sinus sagittalis (s.sag.) (Rex) is a vein of variable size. It 

 arises in the primary vascular coat anteriorly and passes backwards 

 in the middle line to the nodus chorioideus (Rex) — a triangular 

 venous plexus in the paraphysial region (nod.ch.). At about the 

 middle of its length it is considerably strengthened by the addition of 

 a dorso-median cerebral vQin (Rex, translated), bringing the blood from 

 the hemispheres. The vein arises by the fusion of numerous factors 

 from the ventral and mesial surfaces of the hemispheres, and, pass- 

 ing up between them in the sagittal cleft through the subdural space, 

 enters the sinus sagittalis. It is not always possible to trace the sinus 

 anterior to the entry of this vein. In any case it is very small. Rex 

 has described two dorso-median cerebral veins, but only one has been 

 found. It is possible he may have confused the mesial cerebral artery 

 with the venous system (see p. 245). The blood from the various 

 plexuses within the ventricles of the brain (see under 'Arteries') is 

 also returned to the nodus chorioideus by numerous small veins. 



The blood is carried from the nodus chorioideus by a pair of veins, 

 one of which runs from each lateral angle of the triangular nodus. 



The oblique cranial veins (v.cr.ob.) (Venae craniales obliquae, 

 Gaupp, Frog) pass obliquely from the nodus chorioideus between 



