NERVE IMPULSES AND REFLEX ACTION 321 



a nerve is cut and the ends put together ever so carefully, still 

 no impulse will pass over the break. Cutting electric wires 

 in no way impairs them; even though the ends be put to- 

 gether carelessly the current will pass along perfectly, if only 

 there is good contact. Lastly, the nerve fibre is a poor 

 conductor of electricity. 



Taking all these facts together, it would seem that the 

 nerve impulse is not exactly like any other kind of force with 

 which we are acquainted. Although it certainly resembles 

 electricity in many respects, at present it is regarded as a 

 special kind of impulse that travels rapidly through the nerve 

 fibre from any point where it may be started to the other 

 end. 



Nerve impulses may be instituted by many different 

 methods. In the body they usually start from some part of a 

 neuron, but we do not yet know the method by which this 

 is brought about. Impulses may also be started artificially. 

 If an electric shock is sent into a nerve, an impulse is excited 

 and travels to the nerve ending; if the nerve is pinched or cut, 

 an impulse starts from the point of injury. If a hot body 

 touches the nerve, or certain chemicals are dropped upon it, 

 these will also give rise to a nerve impulse. In some nerves 

 an impulse is started by light, in others by sound etc. 



CARE OF THE BRAIN 



Under the conditions of modern life to a far greater extent 

 than in earlier centuries it has become necessary for each in- 

 dividual to use his brain. While some occupations require 

 this more than others, there is none in which one is not helped 

 in the achievement of success by having a well-trained and 

 active brain. Education gives this training. As the years 

 of school life pass, the brain not only obtains information, 

 but it learns how to act; it grows stronger by use just as 

 muscles do. 



We sometimes hear of persons whose health has broken 



