INTELLIGENCE, POWER, 



the brain and sympathetic nervous system, but it increases 



the effect of the sole agent of flash energy, namely, adrenalin. 



On the other hand, total excision of the thyroid gland 



FIG. 20. The nervous system of the insect (grasshopper). 



causes a state of low metabolism, a cold, drowsy, lethargic, 

 almost vegetative state. In this state, a hypodermic injec- 

 tion of even a syringeful of adrenalin has little or no effect 

 upon the heartbeat, the blood pressure, and the mental 

 and the emotional state. In the normal state, a few drops 

 of adrenalin injected hypodermically may cause sweating, 

 tremors, dilation of the pupils, weeping, and such an 

 increase in the blood pressure and in the activity of the 



190 



