THE NERVOUS SYSTEM 



409 



The vastly complex structure by which each cell is cross con- 

 nected to thousands of others, the 

 tree-like branching of the nerves, the 

 grouping in larger fibers and passage 

 from one part to another of the brain 

 and spinal cord, all will have to be 

 omitted. We know that it is the 

 most complicated organ in the world 

 but we are far from a complete 

 understanding of its structure, much 

 less its' mode of operation. 



Experiment and disease have 

 shown that the cerebrum is the 

 center of intelligence, thought, 

 memory, will, and the emotions. 

 It is the region of conscious sensa- 

 tion, by which we perceive all that 

 goes on about us, and in it arise 

 the impulses which produce all our 

 voluntary motions. 



Cerebellum. The cerebellum is 

 situated behind and below the cere- 

 brum, is much smaller, is not divi- 

 ded, and has shallower and more 

 regular convolutions. Its function is 

 mainly to regulate and harmonize 

 (coordinate) muscular action. This 

 is very essential. When we run, or FIG. 132. Central organs of the 

 skate, or walk, or swim, or throw a nervous system. F, TO, frontal, 



temporal and occipital lobes of the 



ball, we use nearly all of the five cere brum; C, cerebellum; p.pons 

 hundred muscles of our body, varolii; mo, medulla oblongata; 



Each muscle fiber is controlled by a n ^~ ms : upper and lower limits of 



* the spinal cord; CVII, 8th cervical 

 nerve; each nerve impulse must nerve; DXII> 12th dorsal nerve. 



reach its muscle at the proper in- (Quain after Bourgery.) From 



stant. When we stop to analyze the Kell gg- 



simplest act and think how many muscles are made to work to- 



