HOW THE GLANDS INFLUENCE THE MIND 171 



ing stamp of the internal secretions upon mind, character and 

 conduct. 



Instinct and Behaviour 



The sex instinct, analyzed as an endocrine mechanism, pro- 

 vides the clue to the understanding of all instinct and behaviour. 

 If the post-pituitary regulates the maternal instinct, then its 

 correlates: sympathy, social impulses, and religious feeling, must 

 be also influenced, and so is furnished another example of a 

 chemical control of instinctive behaviour. McDougall, once of 

 Oxford, now of Harvard, introduced into psychology the idea 

 of the simple instinct as a unit of behaviour, regarding the most 

 complex conduct as a compounding of instincts. The instinct 

 itself he analyzed into three elements: a specific stimulus-sensa- 

 tion, an emotion following, all ending in a particular course of 

 muscular reaction. Translated into endocrine terms, what hap- 

 pens may be pictured as a series of chemical events. 



When the activity of a ductless gland rises above a certain 

 minimum, its hormones in the blood sensitize, as a photographic 

 plate is sensitized, a group of brain cells, to respond to a message 

 from the outside world, with a definite line of conduct. There 

 is a registration by the brain cells of the presence of the specific 

 stimulus. Then there is communication by them with the en- 

 docrine organs. As a result, some of them s*re moved to further 

 secretion, and others are paralyzed or weakened. In consequence 

 of changes of concentration in the blood of the various internal 

 secretions, tensions, movements and tumescences, as well as re- 

 laxations, inhibitions and detumescences, occur throughout the 

 vegetative system — the blood vessels, the viscera, the nerves and 

 the muscles. Each wires to the brain news of the change in it. 

 In addition, the brain cells themselves are excited or depressed 

 by the new hormones bathing them. In their final fusion, the 

 commingling vegetative sensations constitute the emotion evolved 

 in the functioning of the instinct. 



To lower the new tensions throughout the vegetative system 

 to the normal range, the instinctive action is carried out. This 

 superficially is regarded as the essence of the instinct. As a 

 matter of fact, it is only the endpoint of a process, the resultant 

 of a drive to restore equilibrium within the organism. It may 

 all happen in less time than it takes to tell about it. 



