RELATIONS OF THE ADULT PINEAL ORGAN 413 



and pons Varolii are not represented in the diagram. The drawing 

 can thus show the internal occipital vein which lies above and external 

 to the tentorium. Here it issues from the parieto-occipital fissure ; 

 near its termination it crosses the 

 free border of the incisura tentorii 

 and joins the great cerebral vein 

 between the splenium of the corpus 

 callosum above and the pineal body 

 which lies below and internal to it. 

 In this position it would be in 

 direct relation with a pineal tumour. 

 Fig. 279, a transverse and approxi- 

 mately vertical section, gives a 

 notion of the parts in close re- 

 lationship to the pineal body very 

 different from that obtained from 

 Fig. 278, since it passes through 



the posterior part of the fornix and FlG - 276.— Lateral Radiograph of the 



Skull of a Patient, aged 50, show- 

 ing the Typical Appearance of 

 Calcification cf the Pineal Gland. 



great cerebral vein, which lie above, 

 the pulvinares of the optic thalami, 

 which are lateral, and the superior 

 colliculi and aqueduct, which lie 



below. The close relation of the 



cavity of the lateral ventricle, choroid plexus, fimbria, and tela choroidea 

 are also readily 

 appreciated in this 

 section. 



The exact posi- 

 tion and relations 

 of the pineal body 

 are specially well 

 seen in Fig. 280. 

 It is approximately 

 conical in form, 

 slightly flattened 

 from above down- 

 wards, and aver- 

 ages about 8 mm. 

 in length. The 

 base of the gland is 

 directed forwards 



and slightly upwards. Its position, which is very constant, is primarily 

 determined by that of the superior or habenular commissure and the 



Fig. 277. — Median Sagittal Section of Brain. 



