434 THE PINEAL ORGAN 



system above the aqueduct becomes distended and internal hydrocephalus 

 results. Pressure on the vein of Galen by the growth may also play a 

 part in the development of the hydrocephalus. 



The floor of the third ventricle is depressed. The hypophysis is 

 pressed upon and the hypothalamus distorted. It is this change as well 

 as the direct invasion which occurs which probably accounts for the 

 changes in growth and sexual development and other hypothalamic 

 signs which are sometimes seen. Extension may occur into the cerebral 

 hemispheres by direct invasion. 



Haemorrhage occurs into these growths, and terminally haemorrhage 

 into the ventricles is not an uncommon finding. Changes are also found 

 around the medulla, there usually being a very well-developed pressure 

 cone. 



