A STUDY OF THE NERVOUS SYSTEM 283 



the less. Down among his nerve cells and fibers the mole- 

 cules are counting it, registering and storing it up to be 

 used against him when the next temptation comes. Noth- 

 ing we ever do is, in strict scientific literalness, wiped out. 

 Of course this has its good side as well as its bad one. 

 As we become permanent drunkards by so many separate 

 drinks, so we become saints in the moral, and authorities 

 in the practical and scientific spheres, by so many sepa- 

 rate acts and hours of work. Let no youth have any 

 anxiety about the upshot of his education, whatever the 

 line of it may be. If he keep faithfully busy each hour 

 of the working day, he may safely leave the final result 

 to itself. He can with perfect certainty count on waking 

 up some fine morning, to find himself one of the compe- 

 tent ones of his generation, in whatever pursuit he may 

 have singled out.' 71 



8. HYGIENE OF THE NERVOUS SYSTEM 



Changes in the Nervous System during Life. The nervous 

 system of a child at birth differs in many ways from that 

 of an adult. In the first place the nerve cells in the cortex, 

 when first formed, are more or less spherical in shape. 

 During development, however, the axis cylinder and the 

 various branching processes grow out through the tissues 

 from the body of each cell something as roots work their 

 way through the soil. In this way different nerve cells 

 are brought into relation with each other and with different 

 parts of the body. Again, when first formed, axis cylin- 

 ders are naked and they only gradually become covered 

 with a medullary sheath. The central nervous system also, 

 like other parts of the body, increases greatly in size, es- 

 pecially -during the early years of life. Both growth and 

 development^ however, are slow, and hence only by degrees 

 do we get control over the various organs of the body. 



1 Professor James, " Psychology." Henry Holt & Co. 



