CHAPTER XXII 



FUNCTIONS OF THE NERVOUS SYSTEM 



430. In a broad sense, the functions of the nervous sys- 

 tem may be said to be to bring its possessor into due rela- 

 tion with the universe of which he is a part, and to enable 

 him to live that life to which his organism is adapted ; to 

 supply channels of communication between all parts of 

 the body ; to supervise, direct, and control all the con- 

 scious and unconscious activities of the organism. More 

 specifically they are, in the case of man, sensations, gen- 

 eral and special ; regulation of all motion ; control of all 

 vital processes ; and the manifestation of mental opera- 

 tions, thought, will, and emotion. 



431. Sources of Knowledge. We have two sources of 

 information respecting the action of the various parts of 

 the nervous system. There is, first, observation upon 

 human subjects. Obviously few experiments can be made 

 upon man himself, but by careful study of man in health 

 and of symptoms shown in diseases which affect the brain 

 and nerves, much has been discovered. The second source 

 of knowledge is from experiments upon animals. Electri- 

 cal stimulation acts upon the nerves much as does the 

 natural nervous stimulus, and by its use in the physiologi- 

 cal laboratory, and by the destruction of one part or another 

 of the nervous system of an animal, the paths of transmis- 

 sion of impulses and the functions of the different parts 



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