CHAPTER XII 

 THE NERVES AND SPINAL CORD 



216. Cells act together. We have seen that the cells 

 of the body eat and breathe, and that oxygen burns 

 their food and bodies, produces heat, and gives them 

 power for their work. Each cell is thus a complete ani- 

 mal, like the ameba. But millions of amebas tied together 

 in the shape of the body would not act like a man, for 

 no two would act together, but they would fight and strive 

 to get away from each other. The cells of the body are 

 tied together by strings of connective tissue. But they are 

 well-trained servants, and all obey the mind. They work 

 so well together that we do not think of our bodies being 

 made of separate cells. 



217. Nerves. The mind lives in a few cells and rules 

 all the rest. From these cells, little threads called nen>es 



A nerve thread (X 400). 

 a central conducting fiber. b covering of fat. 



go to every part of the body and touch every cell. The 

 mind and the cells talk to each other over these threads, 

 just as you can talk to a friend over the telephone. A 

 nerve thread is like a very fine wire covered with a kind 

 of fat. It is so small that a microscope is needed to see it. 

 Many of these threads run together in bundles, which we 



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