OSHEA — ASPECTS OF MENTAL ECONOMY. 157 



ter may in a well organized brain be utilized in a different one; 

 thus I may be producing a large amount of force in the motor 

 areas of my brain but be employing it in the reflective, the 

 thought regions. If I exercise any certain parts of the cere- 

 brum more than others, energy tends to flow into them and 

 out of the unused areas. Cerebral energy may not inappro- 

 priately be likened to water in respect of its tendency to seek 

 a level ; if it be drawn out in one quarter, it will rush in 

 from others to preserve the equipoise. This theory, which is 

 in harmony with our knowledge of the structure of the cere- 

 brum as an instrument for the production and transmission 

 of energy, is also corroborated by the familiar experience of 

 inhibition in daily life. Every one must have observed that 

 when he thinks vigorously, the degree and force of physical 

 action is lessened; and, on the other hand, when the muscles 

 are most active the mind is relatively inert. Xow, it seems 

 to be a rational supposition that mental activity inhibits phys- 

 ical activity, because it draws away from the motor centers 

 energy required for muscular action. When the mathematical 

 part of the brain, for instance, is intensely active, we may con- 

 ceive that, energy from other localities sets in toward this as 

 a focus, and so activity in other regions is lessened; all is ex- 

 pended upon the particular undertaking in hand. 



Now, if this theory be valid, an inference may be drawn 

 from it of vital significance in regard to the value of exercise 

 for brain workers. If the cerebral motor areas be maintained 

 in a vigorous condition ; if the metabolism of the cells be kept 

 at its best, that is to say, then the surplus energy generated 

 here may be utilized in intellectual labor. On the other hand, 

 one who does not use his muscles, who does not stimulute the 

 motor cells, fails to make use of great laboratories for the pro- 

 duction of vital force. A student who, desiring to accomplish 

 the most in his studies, denies himself all physical exercise 

 must, according to our theory, be a loser in the end. And in 

 more ways than one. He not only fails to keep in their prime 

 all the energy-generating powers of the brain, but he really 



