XI 



THE BRAIN 



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the septum lucidum consists of two layers there is a small 

 flattened closed space between these layers in the middle 

 line of the brain ; this is spoken of as the fifth ventricle, 

 but it has no actual connection with the other ventricles.' 

 (See Fig. 163, 5. ) Each lateral ventricle is a cavity of a very 

 peculiar shape, one branch running forwards towards the 

 front end of the hemisphere and one backwards towards 

 the hinder end, and from the latter a third branch runs 

 downwards and once more forwards. These correspond 

 respectively to the chief lobes of which each hemisphere 

 is made up, namely the frontal lobe, the parietal and 



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Fio. 162.— Diagram to show the Shape of the Cavity of the Left 

 Lateral Ventricle, its Connection with the Third Ventricle, 

 AND the Connection of the Latter with the Fourth Ventricle, 



AND hence with THE CENTRAL CaNAL Of THE SFINAL CoRD. 



Drawn from a cast of the ventricles. (After Welcker.) 



c.c. canal of spinal cord ; 4, fourth ventricle ; A.S. aqueduct of Sylvius ; 

 3, third ventricle ; F.M. foramen of Monro ; LV, L T, L V, lateral ventricle 

 vrith its anterior comu, A.C., posterior cornu, P.C., and inferior cornu, I.C. 



occipital lobes, and the temporal lobe. These lobes are 

 marked off on the surface of the hemispheres by fissures, 

 of wliich the most conspicuous are the fissure of 

 Sylvius, and the fissure of Rolando. (See Fig. 168). 

 The cerebellum is firmly connected to the rest of the 

 brain by the transverse fibres which help to form the 



1 The two lateral ventricles, one in each cerebral hemisphere, are 

 reckoned as the first and second ventricles : hence the space between the 

 layers of the septum lucidum ia known as the fifth ventricle. 



