410 THE PINEAL ORGAN 



bundle which joins the plexus of nerve-fibres on the great cerebral vein 

 and its tributaries. The bundle is the nervus conari of Kolmer. Pastori 

 describes both the fine and the coarse nerve-fibres as arising from small 

 sympathetic nerve-cells situated in the ganglion. The fine fibres enter 

 the epiphysis with the vessels contained in the trabecular. 



It is thus possible that some of the fibres may be efferent nerves 

 from the ganglion to the gland, and others afferent from the gland to the 

 plexus of nerve-fibres on the neighbouring vessels, and that these furnish 

 a means by which the epiphysis may be influenced by or act upon the 

 sympathetic system. 



The Vascular Supply of the Pineal Organ 



The arteries of the pineal body are derived from the posterior choroidal 

 branches of the two posterior cerebral arteries. The posterior choroidal 

 artery on each side enters the transverse fissure of the brain between the 

 two layers of the tela choroidea, and gives off small branches near its 

 origin to the pia mater investing the pineal body ; from these branches 

 numerous arterioles enter the capsule and trabecular of the organ, and 

 ultimately give off capillary vessels for the supply of the parenchyma. 

 The capillary net is drained by venules which passing through the 

 trabecular and capsule unite to form a vessel which joins the great cerebral 

 vein of Galen. This terminates in the anterior part of the straight sinus. 



Since a tumour of the pineal organ may by pressure obstruct the great 

 cerebral vein, it is important to know the exact course of this vessel. It 

 will be remembered that the internal cerebral vein on each side is formed 

 in the region just behind the interventricular foramen of Monro by the 

 union of the anterior choroidal vein with the terminal or striate vein, and 

 that the two internal cerebral veins course backwards below the fornix 

 and between the two layers of the tela choroidea or velum interpositum. 

 Here they receive tributaries from the choroid plexus of the third ventricle 

 and optic thalami. They unite near the base of the pineal body to form 

 the great cerebral vein of Galen, which curves upwards in the cisterna 

 vense magnar cerebri around the splenium of the corpus callosum (Fig. 

 274). Here after receiving the right and left basal veins and the internal 

 occipital veins, it opens into the anterior end of the straight sinus, the 

 latter vessel commencing as a continuation of the inferior sagittal sinus. 

 It is important to remember also that some of the superior cerebellar 

 veins run inwards to terminate in the straight sinus or in the internal 

 cerebral veins. 



The opening of the right and left basal veins into the great cerebral 

 vein of Galen has a practical bearing in connection with occlusion of the 

 great vein, for unless the pressure on the great cerebral vein involves 



