CHAPTER XL 

 THE NERVOUS SYSTEM. 



General Functions of the System as a Whole. The ner- 

 vous system is the most delicately organized part of the ani- 

 mal 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, control- 

 ling and regulating their action. Connecting, as it does, all 

 parts of the organism into a coordinate whole, it is the only 

 medium through which impressions are received, and is the 

 only agency through which are regulated movement, secre- 

 tion, 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 instru- 

 mentality of this system, as when volition calls them into ac- 

 tion; 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 perceived 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 exter- 

 nal objects are capable of exciting, the mind would be com- 

 pletely isolated, and could hold no communion with the ex- 

 ternal 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 



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