286 THE GLANDS REGULATING PERSONALITY 



Sea-water contains iodine. People living in contact with sea- 

 water would be apt to get more iodine in their systems, and so 

 a greater degree of thyroid activity. On the other hand, cer 

 bodies and sources of inland water hold something deleterious to 

 the thyroid, so that whole populations in Europe, Asia and 

 America drinking such water have become goitrous and cretinous, 

 and a large percentage straight imbeciles. Endemic cretinism is 

 the name given to the condition. In parts of Switzerland, Savoy, 

 Tyrol and the Pyrenees, in America around some of the Great 

 Lakes, there are still such foci. Marco Polo described similar 

 areas he encountered in his travels through Asia. 



Certain foods with aphrodisiac qualities may act by stimulat- 

 ing the internal secretion of the sex glands. A type of pituito- 

 centric has an almost uncontrollable craving for sweets. Alcohol 

 and the endocrines remain to be studied. 



Light, heat and humidity stand in some special relation to the 

 adrenals. Pigment deposit in the skin as protection against light 

 is controlled by the adrenal cortex. The reaction of the skin blood 

 vessels to heat and humidity is regulated by the adrenal medulla. 

 A change in the adrenal as a response to changes of temperature 

 and humidity in an environment would result in a number of 

 concomitant transformations throughout the body. So variation 

 and adaptation are probably connected. Most Europeans living 

 for a sufficiently long time in the tropics suffer from a combina- 

 tion of symptoms spoken of as "Punjab head" or "Bengal head." 

 The condition is probably the result of excessive adrenal stimu- 



ion by the excessive heat and light of the tropical sun, followed 

 by a reaction of exhaustion and failure, with the con 

 phenomena of a form of neurasthenia. In the section on the 

 pineal gland there was mentioned the relation between light and 



inland in growing animals, and how it serves to 1. 

 in ofaeok the sex-stimulating action of light. The earlier puberty 

 and menstruation of the warmer climates may be explained Bl 

 IB earlier regression of the pineal under the pressure of a gl 

 amount of li^ht playing upon the skin. 



All these, and many more could be cited, are instances of the 

 direct influence of environmental factors upon one or moi 

 endocrines, and so upon the organism as a whole. Indeed, stimuli 

 may be considered to modify an organism only in so far as I 

 mo' glandi of in i Consequently, dim 



factors will tend to make a population possess certain points of 

 resemblance in common. 



