212 Life and Health 



lobes, so that the entire cerebrum is made up of six 

 distinct lobes. 



The cerebrum has a peculiar convoluted appearance, its 

 deep folds being separated by fissures, some of them nearly 

 an inch in depth. 



It is composed of both white and gray matter. The 

 former comprises the greater part of the mass, while the 

 latter is spread over the surface in a layer about one-eighth 

 of an inch thick. The gray matter is the portion having 

 the highest functions, and its quantity is largely increased 

 by its arrangement in convolutions. 



The cerebrum is the seat of the sensations, the intellect, 

 the will, and the emotions. 



324. The Convolutions of the Cerebrum. The convolutions 

 of the cerebrum are without doubt associated with all those 

 higher actions which distinguish man's life ; but all the 

 convolutions are not of equal importance. 



The convolutions in the human brain are more promi- 

 nent than are those in the brain of the higher animals 

 most nearly allied to man, although some species of ani- 

 mals, not especially intelligent, have marked cerebral con- 

 volutions. The higher races of men have more marked 

 convolutions than have those that are less civilized. 



325. Under Surface of the Brain. The under surface 

 of the brain, which rests on the floor of the skull, shows 

 the origin of important nerves called the cranial nerves; the 

 cerebellum ; the structure connecting the optic nerves (optic 

 commissure) ; the bridge of nervous matter (pons Varolii) 

 connecting the two hemispheres of the cerebellum ; and 

 lastly, numerous and well-marked convolutions. 



/ 326. The Cerebellum. The cerebellum, or lesser brain, 

 lies in the back of the cranium and is covered over by 

 the posterior lobe of the cerebrum. It is, as it were, 



