The Brain. 233 



When we walk or run, or even stand still, a number of 

 muscles must act, and act in concert. The nerve impulses 

 originate in the cerebrum, but the cerebellum is the center 

 for harmonizing the action of these various muscles. When 

 the cerebellum is injured, an animal staggers instead of 

 walking steadily. 



Functions of the Spinal Bulb. The spinal bulb is the 

 enlarged part of the spinal cord which is within the cra- 

 nium. From it arise all the cranial nerves except the first 

 five pairs. The spinal bulb is also the center for the con- 

 trol of respiration, of circulation, of swallowing, and perhaps 

 for many other processes. 



Brain Work and Brain Rest. Sleep is not merely rest 

 for the body ; it should be complete rest for the brain. In 

 so far as there are dreams, it would seem to indicate a par- 

 tial activity ; that is, incomplete rest. The brain, like the 

 muscles, needs exercise, and it also needs regular periods 

 of rest. If a nerve cell is not kept active by the passage 

 of nerve impulses through it, it usually dwindles away, 

 and may entirely lose its power. 



Sleeplessness. Intense brain work, without sufficient 

 sleep, is likely to lead to sleeplessness, as when one has 

 some subject of special study in hand and either will not 

 or cannot throw it off. Perhaps inventors are as subject 

 to this sort of trouble as any one class of men. Keeping 

 the blood continually in the brain is likely to lead to a per- 

 manent congestion, or inflammation, that may cause seri- 

 ous, if not fatal, results. 



Fatigue. It is stated that brain workers need more 

 sleep than those who work chiefly with the muscles. Fa- 

 tigue of the voluntary muscles is much more a matter of 



