CHAPTER IX 



THE AUTONOMIC NERVOUS SYSTEM 



THE term which is used as the title of this chapter is 

 employed to cover that part of the efferent system which 

 does not control the skeletal muscles. The negative de- 

 scription seems awkward, hut is nevertheless accurate and 

 final. It is equivalent to the statement that the autoiiomic 

 system regulates the action of the heart, the glands, and 

 all structures in which there is contractile tissue of the 

 kind known as plain, smooth, or visceral muscle. This 

 variety of tissue occurs in the alimentary canal, the 

 gall-bladder, the urinary bladder and the ureters, in the 

 reproductive organs, in the blood-vessels and lymphatics, 

 and in the bronchial tubes. It is also represented, though 

 sparsely, in the skin. It forms the accommodation or 

 focusing muscle of the eye and its presence in the iris makes 

 possible the familiar changes in the size of the pupil. 



The term "autoiiomic" is akin to the political word 

 "autonomy," and implies "self-regulating." A contrast 

 between this division of the nervous system and that 

 which governs the skeletal muscles is suggested. It is a 

 common practice to call the skeletal muscles "voluntary," 

 and to regard the heart and all the organs equipped with 

 plain muscle as "involuntary." The distinction is as apt 

 to mi-lead as to be helpful and it will not be insisted upon 

 here. ( )f coiir-e. it is true that we often have a fore- 

 knowledge of the movements of our skeletal muscle^ which 

 we do not have in any such degree with respect to the other 

 motor elements in the body nor as regards the behavior of 

 the gland-. Hut we must note that much of the activity 

 of the so-called voluntary muscles proceeds with little 

 conscious attention on our part (breathing, balancing), 

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