INTELLIGENCE, POWER, 



lated, there was a grimace, movement of the eyes, puckering 

 of the lips as in whistling, or pointing of the finger. Not 

 only were such gross movements as shrugs of the shoulder 

 and movements of the arms, fingers, toes, and hands pro- 

 duced, but also such motions were produced as are used in 

 running. The question that arises is did an electric current 

 pass from the brain to the contracting muscles ? During 

 the stimulation, the galvanometer indicated the passing 

 of electric currents, in the spinal cord. 



In our own researches on animals we have found that 

 such physical constants as temperature, electric con- 

 ductivity, electric capacity, and electric potential vary in 

 the living brain in the normal state, in the state of excessive 

 activity, and in the state of depression. The administration 

 of thyroxin is followed by an increase in the electric poten- 

 tial, electric conductivity, electric capacity, and tempera- 

 ture of the brain. Thyroidectomy is followed by a slow 

 decrease in the electric potential, electric conductivity, 

 electric capacity, and temperature of the brain. The injec- 

 tion of adrenalin causes an abrupt rise in the electric 

 potential, electric conductivity, electric capacity, and 

 temperature of the brain, followed by an equally abrupt 

 fall in these physical constants. 



In man, thyroid deficiency is attended by a correspond- 

 ingly lowered activity of the brain. Excessive activity of the 

 thyroid gland, whether through hyperplasia of the thyroid 

 gland or through the administration of thyroxin, raises 

 the level of activity of the brain, causing, first, a high 

 normal tone and, if carried to the extreme, excitability 

 and, finally, delirium. 



Not only does the thyroid hormone increase the rate of 

 oxidation in the billions of brain cells but equally increases 

 the activity of the nerve cells constituting the ganglia 

 and nerves of the entire sympathetic system. Not only 

 does thyroxin produce all these fundamen 



188 



