316 NERVES AND THEIR CONTROL 



4. Do you now find it so easy to walk that you can also 

 think of distant or other things at the same time? If so, of 

 what advantage is it to you? 



5. When watching a group of people learning to do anything 

 in concert, as drills of children, etc., or of soldiers, how did the 

 first rehearsal compare with the last ? Note. As soldier after 

 soldier, or child after child, became better able to do his part, 

 so neuron after neuron of the brain and spinal cord became 

 better able to do their parts, until finally there is habitual action. 



6. Explain the following story: "A practical joker saw a 

 discharged veteran carrying his dinner home ; he suddenly 

 called out, ' Attention'; whereupon the veteran instantly 

 brought his hands down, dropping his dinner in the gutter." 



Conclusions. 1. How are habits formed? Illustrate your 

 answer, using the term "nerve cell." 



2. Mention one advantage of a good habit, as walking, etc. 



Observations. 1. Suppose a man must concentrate his mind 

 on just how to walk, or to digest, or to dodge an unexpected 

 blow, or to resist falling, etc. How would it affect the safety 

 of his life ? 



2. Mention as many actions of your body as you can that 

 tend to safety and comfort of life. Are the habits of content- 

 ment and self-control of any value ? 



Conclusions. 1. Write a paragraph on the increased effec- 

 tiveness and power acquired through good habits. 



2. Is it easy to break a habit ? Explain your answer. 



3. Explain the statement, " Life is but a tissue of habits." 



2. HARMFUL 



Observations. 1. Boil a pipeful of tobacco in a pint of water, 

 Put the resulting solution into a small aquarium containing a 

 tadpole or a small goldfish. Results ? 



2. Draw the smoke from 5 or 6 cigarettes through water in 

 the bottle as shown in Figure 80. Pour the liquid into a small 

 aquarium containing a tadpole or goldfish. Results ? 



