246 rUYSIOLOGY. 



bulb may be said to be that part of the spinal cord which 

 is within the cranium. It is enlarged, hence its name, 

 tpinal bulb. From it arise all the cranial nerves except 

 the first five pairs. The spinal bulb is also the center for 

 the control of respiration, of circulation, of deglutition, 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 

 partial activity ; that is, incomplete rest. The brain worker 

 especially needs plenty of sleep ; excellent authorities say 

 at least eight or nine hours. 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 atrophies, and may de- 

 generate. 



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 prone to 

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

 blood continually in the brain, or in any organ, is likely to 

 lead to a permanent congestion or inflammation that may 

 cause serious, 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 

 nervous than of muscular origin. When one is completely 

 " tired out," as he would say, if his mind can be aroused, 

 as by some excitement, he will be found able to expend a 

 good deal more muscular energy. So, too, many persons 

 of slight muscular build, but of great " will power," are 



