Cerebrum. 



109 



450. Base of the Brain, view from below. 



2 / 3 natural size. 



After separation of the tentorium from the pyramids of the petrous 

 bones, and cutting through the origins of the cranial nerves, the Medulla 

 oblongata and the vertebral arteries, the whole brain is taken out of the 

 cranial cavity and turned about, and thereby the base of the brain 

 ig brought to view. Here are seen : 



a) The anterior perforated space, Substantia perforata anterior, 

 which consists chiefly of grey matter; it is divided into a middle and two 

 lateral spaces, which serve for the transmission of bloodvessels. In front 

 of the lateral portions a pyramidal grey eminence, the Trigonium olfactorium 

 lies; it is prolonged into the Nervus olfactorius. 



b) The optic commissure or Chiasma nervorum opticorum, is 

 formed by the two optic tracts, Tractus optici, which wind across 

 the under surface of the Pedunculi s. Crura cerebri; from the chiasma, 

 the round optic nerves, Nervi optici, arise. 



15* 



