THE NERVOUS SYSTEM 2Q5 



injury are suspended. The leg will kick when the foot is 

 tickled, etc. A surgeon tickled the foot of a man whose 

 spinal cord was injured, and the feet kept up a vigorous 

 kicking. He asked the man if he felt it ; he said, " No, 

 but you see that my feet do." On carefully testing the 

 sensibility of such a man, a line can be traced girdling the 

 body, dividing the sensitive from the insensitive part. The 

 brain also may act seemingly in a reflex manner as in 

 cases of somnambulism, or sleep-walking. 



546. When one is learning new movements, such as 

 walking, skating, writing, riding a bicycle, each movement 

 is a voluntary one as far as the will is capable of watching 

 so many muscles. The movements are, therefore, slow 

 and awkward. After the movements have been made 

 many hundreds of times, they becomes easy and graceful, 

 and also less voluntary. Finally, one may learn to walk, 

 cycle, or play the piano with the attention fixed on some- 

 thing else. Such movements are called " acquired re- 

 flexes." There is evidence to show that the axons become 

 covered with a medullated coat, as each new pathway and 

 tract is beaten through the nervous system by repeated ex- 

 periences. Thus the structure, like the habit, becomes fixed. 



547. Reflex Action and Education. Education of reflex 

 action consists mainly of the formation of habits. The im- 

 pression on the nervous system from the training is made 

 chiefly on the spinal centers. When the muscles of the 

 hand are educated, it is really the spinal cells that are 

 educated. During youth, one is always acquiring good 

 habits or bad habits. The habit of an upright, easy walk, 

 the habit of dropping into a stooping posture, of putting 

 the hands in the pockets, of making wry faces, of mum- 

 bling and stammering, or of talking distinctly and without 

 hesitation, may be acquired, and will probably remain 

 ihrough life, tor impressions made on the nervous system 

 in youth are lasting. The habit of Beating temperately of 



