THE NERVOUS SYSTEM 303 



motor area containing a number of centers which, when 

 stimulated by electric needles, produce a movement in a 

 particular part of the body. There is in the ape's brain, 

 for instance, a center for the movement of the fingers, 

 another for the forearm, another for the shoulder muscles, 

 others again for various parts of the hind leg and trunk. 

 When these centers are cut out the animal has difficulty 

 in making movement in a corresponding part of its body. 

 When brain tumors occur in the motor area their precise 

 location is often indicated by the inability of the patient 

 to perform certain movements. Many such cases have 

 been cured by making an opening through the skull over 

 the area indicated and removing the tumor. 



Abnormal conditions of the brain are very frequently 

 correlated with epilepsy and insanity. There is a remarka- 

 bly close relationship between the activities of our 

 brains and the working of our minds. It is not possible 

 to have a healthy mind in a diseased brain, and as the 

 brain is an especially delicate and sensitive organ it 

 quickly feels the effect of injurious agencies. Nearly a 

 fifth of the circulating blood goes to supply this organ. 

 Nervous tissue absorbs a relatively large amount of 

 material from the blood and it is the seat of active 

 metabolic changes. This circumstance accounts in large 

 part for the necessity for sleep which is a period of rest 

 and restoration. During childhood, which is a time of 

 rapid growth and active exercise, more sleep is required 

 than later in life; but in all periods of life sleep cannot be 

 dispensed with for long without producing very serious 

 results. 



