CHAPTER XL 

 THE NERVOUS SYSTEM. 



General Functions of the System as a Whole. The nervous 

 system is the most delicately organized part of the animal body. 

 Its sensory terminations receive impressions which are conducted 

 to the centers; it conveys impulses from the centers to the different 

 parts of the body, controlling and regulating their action. Con- 

 necting, as it does, all parts of the organism into a coordinate 

 whole, it is the .only medium through which impressions are re- 

 ceived, and is the only agency through which are regulated move- 

 ment, secretion, calorification and all the processes of organic life. 

 This system, ramified throughout the body, connected with and 

 passing between its various organs, serves them as a bond of union 

 with each other, as well as with the brain. The mind influences 

 the corporeal organs through the instrumentality of this system, 

 as when volition calls them into action; on the other hand, 

 changes in the organs of the body may affect the mind through 

 the same channel, as when, for instance, pain is mentally per- 

 ceived when the finger is burned. Thus it is that the nervous 

 system becomes the main agent in what is known as the "life 

 of relation;" for without some medium for the transmission of 

 its mandates, or some means of receiving those impressions which 

 external objects are capable of exciting, the mind would be 

 completely isolated, and could hold no communion with the 

 external world. 



It should not be understood, however, that the nervous system 

 cannot operate independently of mental influence. All those 

 manifestations of nervous activity connected with the perform- 



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