THE BRAIN. 249 



it is supposed that part of the cerebrospinal fluid is 

 pressed out into the spinal cavity, thus relieving the pres- 

 sure in the brain cavity. 



Relative Activity of Gray and White Matter. The 



gray matter is, physiologically, more active than the white, 

 and in keeping with this is the fact that the capillary 

 network is closer in the gray matter than in the white. 

 This is true of the spinal cord as well as of the brain. 



READING. Brain-work and Over-work, Wood ; The 

 Brain and its Functions, Luys. 



Summary. i. The outside of the brain consists of gray matter, 

 the inside of white matter. 



2. The twelve pairs of cranial nerves are distributed to the head, 

 with the exception of the tenth and part of the eleventh. 



3. The cranial nerves include all the special senses but that of 

 touch. 



4. Each hemisphere of the brain is connected with, and has chief 

 control of, the opposite half of the body. 



5. The gray matter of the cerebrum is the seat of the will, sensation, 

 thought, and emotion. 



6. The cerebellum regulates voluntary motion. 



7. Many of the cerebral functions have been located. 



8. The brain needs rest. In sleep less blood flows through the 

 brain. 



9. Work reduces the size of nerve cells. During rest they increase 

 again. 



Questions. i. Is there any special reason why the "speech cen- 

 ter" should be in the left cerebral hemisphere ? 



2. Why does a light lunch sometimes enable one to go to sleep 

 after mental work ? 



3. Why is it uncomfortable to hold the head down ? 



4. How does the nervous system resemble a telegraph system ? In 

 what respects are the two unlike ? 



5. Name some remedies for sleeplessness. 



