THE BRAIN. 247 



able to do more work with the muscles than others with 

 larger muscles and less will. During fatigue the cell bodies 

 are found to decrease in size, but there is no discernible 

 change in nerve fibers as a result of fatigue. 



Control of Mind. But the brain worker should not 

 only be able to sleep regularly and long enough ; he ought 

 to be able to throw off his mind any subject, and take rest 

 while he is awake. If one allows himself to think about 

 mental work while eating, the process of digestion will not 

 go on well. 



Habit of Resting the Brain. The student should ac- 

 quire the power and cultivate the habit of having, so far 

 as possible, regular hours for work, and of completely 

 throwing aside his work and worry at stated times. In 

 seeking recreation it is well to choose that which will 

 necessitate giving the attention to something entirely dif- 

 ferent from the daily work. For this reason chess may 

 be no real recreation for the student, while a game of 

 tennis, boxing, or other competitive exercise is likely to 

 accomplish this very desirable object. A walk may put 

 the muscles into play, but if the mind is still intent upon 

 the line of work maintained throughout the day, the exercise 

 may prove of little benefit. He may return more tired 

 than when he set out. The exhilaration of horseback rid- 

 ing may prove far better, though perhaps involving much 

 less muscular exertion. 



Nervous Tissue least affected by Starvation. It is 

 worthy of note that in fasting the nervous tissue is less 

 reduced than any other tissue, being scarcely diminished 

 by complete starvation. 



Blood Supply of the Brain. Blood is supplied to the 

 brain through four arteries : the right and left internal 



