THE VASCULAR SYSTEM 247 



the posterior end of the cerebrum and the corpus opticum, and dis- 

 charge into the venous plexus covering the sinus endolymphaticus 

 (plexus lateralis, Scholb). About midway they receive lateral tribu- 

 taries on either side. 



Each lateral cerebral vein collects from the dorsal and lateral 

 regions of the fore-brain. 



The dura mater covering the diencephalon is fairly free from 

 veins, and no vessel of any size occurs in it. The primary vascular 

 coat, on the other hand, possesses a comparatively rich network of 

 veins. This network collects into two dorsal longitudinal vessels 

 (v.long.di.) near the middle line, which apparently correspond with 

 the single, median, Vena longitudinalis diencephali (Gaupp) of the 

 Frog. From the anterior end of these veins one or two vessels pass 

 out through the subdural space and discharge into the plexus cover- 

 ing the sinus endolymphaticus. 



The blood from the cerebellum collects into a vessel which enters 

 the plexus covering the fourth ventricle. 



The lateral plexus (pl.l.), covering the sinus endolymphaticus 

 (Scholb's name is retained for sake of convenience), is a coarse venous 

 network forming a hollow pyramid with a triangular base on either 

 side of the diencephalon, the base being directed inwards and the 

 apex outwards. The blood gathers into a single large vessel at the 

 apex of the pyramid and passes out of the cranial cavity, ventral to 

 the R. oph. profundus V, and enters the Vena petrosa lateralis (q.v.). 

 This is the Vena cranialis pro-otica (v.cr.pr-ot.) (Gaupp), and is the main 

 venous exit from the cranial cavity. It corresponds with the Vena 

 cerebralis anterior of van Gelderen. 



The anterior part of the fourth ventricle is roofed over by a very 

 rich plexus, more or less rhomboidal in shape, and communicating 

 at its anterior corners with the lateral plexuses. There is usually a 

 fairly pronounced vessel running transversely across the anterior 

 edge of this plexus. Entering the plexus dorsally are two longitudinal 

 medullary veins which pass anteriorly along the borders of the pos- 

 terior part of the fourth ventricle. They evidently correspond with 

 the Venae craniales post-occipitales (Gaupp) of the Frog, but they 

 are not nearly so pronounced in the Salamander, and do not com- 

 municate, other than very indirectly, with the Vena spinalis superior. 



Rex has described for Triton several basal veins entering this 

 plexus from the ventral side of the medulla oblongata, but, while the 

 veins from the ventral side of the medulla of Salamandra certainly 

 do communicate quite freely with the plexus, no vessels of sufficient 

 distinction to warrant a name have been found. 



