CHAPTER XLII 

 THE NERVOUS SYSTEM 



Vocabulary 



Convolutions, irregular grooves in the surface of the cerebrum. 



Voluntary, under control of the will. 



Harmonize, to coordinate, to make to work together. 



The brain is the one organ which in man is capable of greater 

 development than any other animal. No amount of training will 

 enable us to compete with the fish, bird, dog, or snake in speed, 

 strength, locomotion, or keenness of sense. Practically every 

 animal excels man in some way and the one thing that makes 

 man their superior is his greater intelligence, which means greater 

 brain development. 



Despite this, we often devote more attention to other lines, in 

 which we cannot hope for really useful success, and leave to very 

 indifferent care the training of our one source of superiority. 



While we cannot deal with the structure of the brain in detail, 

 the need of some controlling organ to regulate the complicated 

 functions of any animal's body is very apparent and we must 

 needs take up its study, if only very briefly. 



Structure. The brain consists of three general regions, the 

 cerebrum, the cerebellum, and the spinal bulb. Connected with it 

 are the spinal cord and nerves which together with the brain com- 

 pose the central nervous system. 



Cerebrum. The cerebrum constitutes about nine-tenths of the 

 brain; it occupies the upper part of the skull and is divided into 

 two halves or hemispheres. Its surface is deeply folded in ir- 

 regular grooves (convolutions) and consists of gray nerve cells, 

 while internally the bulk of its tissue is made up of white nerve 

 fibers. 



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