222 



THE KXltVOUS SYSTEM 



entire body possesses. The brain of man is heavier than that 

 of any other animal, except the elephant and whale. 



10. The Cerebrum. The brain proper, or cerebrum, is the 

 largest of the intracranial organs, and occupies the entire upper 

 and front portion of the skull. It is almost completely bisected 

 by a fissure, or cleft, running through it lengthwise, into two 

 equal parts called hemispheres. The exterior of these hemi- 



FIG. 55. UPPER SURFACE OF THE CEREBRTTM 

 A, Longitudinal Fissure B, The Hemispheres 



spheres is gray in color, consisting chiefly of nerve-cells, arranged 

 so as to form a layer of gray matter one-fifth of an inch in 

 thickness, and is abundantly supplied with blood-vessels. The 

 interior of the brain, however, is composed almost wholly of 

 white substance, or nerve-fibres. 



11. The surface of the cerebrum is divided by a considerable 

 number of winding and irregular furrows, about an inch deep, 



10. 'Where is the cerebrum located ? 

 hemispheres. The interior. 



How is it divided ? Describe the exterior of the 



