SELF 229 



consequent increase of the circulation to the brain. 

 These accelerate the action of the heart, which modifies 

 the whole vascular system ; or by the fixedness of the 

 muscles, controlling the eyes, or other organs of sense. 



BRAIN ACTIVITY EXHAUSTING. What we call mental 

 action is more exhausting of the metabolic process 

 of the physical, or digestive system, than any other 

 labor of the body. The more intense the thinking the 

 more rapid is the flow of blood to the brain. Muscular 

 tissue is heavily stocked with a large reserve of glycogen, 

 which is potential energy, while the nerve tissue, is only 

 served with this reserve from the muscular tissue, as 

 it is wanted. It would thus appear that the rest of the 

 organism is there for the purpose of furnishing the 

 nervous system with the energy required for the mental 

 operations, and the control over this energy is given 

 to the nervous system. The body tissues will exhaust 

 themselves, in order to keep the brain at work, as is 

 frequently apparent in persons of weak body and active 

 mind, all the sustentation goes where it is summoned 

 by the nervous system, to the brain, at the expense of 

 mere muscular energy. It is thus that disease is some- 

 times a stimulation of the brain. Some wonderful men- 

 tal work has been done by brains, whose poor weak 

 bodies have been kept exhausted, in supporting in vigor, 

 a healthy brain. In starvation, the body tissues will 

 exhaust themselves in supporting the brain, the latter 

 remaining healthy, until the vital organs of digestion 

 cease to operate. However, when death comes, the men- 

 tal action ceases first, but only on account of the ex- 

 haustion previously, of the flow of the arterial blood, 

 charged with vital energy, to the brain. 



Cuvier said: "The nervous system is, at the bottom, 

 the whole animal; the other systems are .there only to 

 serve it." 



