THE BASAL GANGLIA. 



301 



pital; and the fissure of Sylvius, between the temporal lobe below 

 and the frontal and parietal above it. 



Important note. The fissure of Rolando is often called the central fissure, 

 and the convolutions in front of and behind it, are called the central convolutions 

 (anterior and posterior central). 



Within the white substance of the hemispheres are the largest 

 ganglia in the brain, and since they are situated near the base, 

 they are called basal ganglia. They are the optic lhalamus, the 

 lentiform nucleus, and the caudate nucleus (Fig. 195). The white 



FIG. 193. MEDIAN SURFACE OF A HEMISPHERE, SHOWING THIRD AND FOURTH 

 VENTRICLES; ALSO THE CORPUS CALLOSUM DIVIDED, AND THE STRUCTURE OF THE 

 CEREBELLUM WITH THE PONS IN FRONT OF IT. THE PITUITARY BODY is SUSPENDED 



FROM THE FLOOR OF THE THIRD VENTRICLE. ( 



matter between the optic thalamus and the other two, constitutes 

 the internal capsule. Here are the fibers which connect centers in 

 the cortex with those in the spinal cord; hence the great importance 

 of the internal capsule. 



The white fibers of the cerebrum are classified in three groups: i. those 

 which connect different parts in the same hemisphere, or association fibers; 

 (Fig. 201) 2. those which connect parts in one hemisphere with similar 

 parts in the other, or commissural fibers; 3, those which connect the 

 cortex with the ganglia of the brain and spinal cord, or projection fibers 

 (Fig. 192 shows projection fibers of the right half of the brain). 



The hemispheres are not solid, but each encloses a cavity 

 called the lateral ventricle, shaped like the italic letter / with a 



