THE BACKGROUNDS OF PERSONALITY 201 



the nerve impulses is created. We have here an illustration of 

 internal secretion lack actually producing gross changes in the 

 brain. But without a doubt, most endocrine influences upon the 

 brain, at work every minute and second of its life, are the subtle 

 ones of molecular chemistry and atomic energetics. We know 

 that such mental qualities as irritability and stupidity, fatiga- 

 bility, and the power to recover quickly or slowly from fatigue, 

 sexual potency and impotence, apathy and enthusiasm are en- 

 docrine qualities. We know also that the thyroid dominant tends 

 to be irritable and excitable, the pituitary deficient to be placid 

 and gentle, the adrenal dominant to be assertive and pugnacious, 

 the thymus-centered to be childish and easy-go-lucky and the 

 gonad deficient to be secretive and shy. This brings us to the 

 relation of the internal secretions to the type of personality as a 

 whole. 



