STRUCTURE OF THE EHCE2HALON. 



19? 



presents a thick posterior border in front of the tentorial 



attachment of the falx, and at its fore part curves downwards 



behind the ethmoidal 



attachment of that 



structure, to become 



continuous with a 



thin lamina which 



completes the floor of 



the cavity of the brain 



in the middle line. 



The parts of the 

 hemispheres, which 

 project forwards, rest- 

 ing on the anterior 

 fossa of the skull, over 

 the orbits, are called 

 anterior lobes ; the 

 parts above the cere- 

 bellum are the poste- 

 rior lobes, and the 

 parts turning down 

 over the crura cere- 

 bri, and resting in 

 the middle fossae, on 

 the sphenoid and tem- 

 poral bones, are dis- 

 tinguished as the. 

 middle lobes. 



146. If a human 

 brain, or still better, 

 the brain of any of 

 the domestic quadru- 

 peds, be examined, 

 and the cerebellum 

 be turned aside from 



&' 102. DIAGRAM OF BRAIN. ^ , Spinal 

 cord ; b, b, cerebellum, divided and, 

 above it, the valve of Vieussens partially 

 divided ; c, corpora quadrigemiiia ; d, d t 

 optic thalami ; e, pineal body ; /, /, cor- 

 pora striata ; g, g, cerebral hemispheres 

 in section; 7t, corpus callosum ; i, fornix; 

 I, l f lateral ventricles ; 3, third ventricle; 

 4, fourth ventricle ; 5, fifth ventricle, 

 bounded on each side by septum lucidum. 



the hemispheres, the isthmus will be brought into com- 

 plete view, and there will be displayed above it an eleva- 

 tion divided by a crucial depression into four parts, and 

 called on that account corpora quadrigemina. Two tracts 

 will also be seen, about half an inch separate, adherent to 



