DISEASES OF THE NERVOUS SYSTEM. 



By W. H. Harbaugh, V. S. 



[Revised by John R. Mohler, V. M. D.] 



THE NERVOUS SYSTEM. 



The nervous system is the distinguishing feature of animal life. 

 Without it there can be no intelligence, no instinct, no sensibility, no 

 perception ; in fact, existence would be nothing more than vegetable 

 life. 



The senses — touch, taste, sight, hearing, smell — all depend on the 

 nervous system. Motion depends on it. A muscle can not contract 

 without receiving the stimulus from the nervous system. For ex- 

 ample, if a nerve passing from a nerve center to a muscle is severed, 

 the particular muscle that is supplied by the cut nerve is paralyzed. 



The nervous system is often studied in two divisions — the cerebro- 

 spinal division and the sympathetic division. 



The cerebrospinal division consists of the brain and spinal cord, 

 nerves, and ganglia. The nerves of this division convey the impulses 

 of motion and sensation and supply all parts which are under the 

 control of the will. For example, the voluntary muscular tissue 

 includes all the muscles which act as the will directs. Another ex- 

 ample: If anything comes in contact with any part of the skin, the 

 impression is immediately perceived. All the special senses belong 

 to this division. 



The sympathetic division consists of nerves and ganglia. The 

 muscular tissue, which acts independently of the will — as, for exam-, 

 pie, the stomach, intestines, womb, blood vessels, ducts, etc. — is called 

 involuntary muscular tissue, and receives nervous stimulus from the 

 sympathetic division. 



The brain, spinal cord, and the ganglia are the central organs of 

 the nervous system. The nerves conduct the nervous influence. The 

 nerves terminate differently according to their function. The termi- 

 nations are called end organs. The terminal end organs in the skin 

 and other parts endowed with sensation receive the impressions, which 

 are conveyed to the brain, where they are appreciated. They are so 

 sensitive that the most gentle zephyr is perceived. They are so 

 abundant that the point of the finest needle can not pierce the skin 

 without coming in contact with them, and the sensation of pain is 



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