CHAPTER XVIII. 

 THE NERVOUS SYSTEM AND ITS FUNCTIONS. 



1. Introductory. If the inside of your nose be tickled, 

 you cannot help sneezing ; it seems so natural to 

 sneeze when anything irritates the nostrils that probably 

 you never thought about it at all. But if you do think 

 about it, you will find that it is something quite curious 

 and interesting. If some one puts a soft feather up your 

 nose, neither the larynx, nor the lungs, nor the chest- 

 muscles, nor the diaphragm, are interfered with; yet 

 they all (p. 174) set to work at once to help the nose to 

 get rid of what is worrying it, and they do this without 

 paying any heed to your will. In other words, they act 

 involuntarily. They do, apparently of themselves, what 

 is likely to help the nose, and they set to work in a very 

 orderly way. If any one of them failed to do its share 

 of the work, or worked never so little out of its turn, no 

 useful sneeze would be produced. 



How the nose obtains such ready and well-planned 

 help from all these organs which lie at a distance from 

 it, we will try in this chapter to explain. 



2. Other Examples of the Help which our Organs give 

 to One Another. Coughing (p. 174) is one that will of 



i. What results from irritating the inside of the nostrils? What 

 organs work together to produce a sneeze ? What is meant by say- 

 ing that they act " involuntarily " ? What would happen if any one 

 of them did not act "just right" ? 



