214 Changing Human Nature 



well known prevalence of goiter in the mountainous regions 

 of the European continent, and the very frequent association 

 between such goiter and retarded mental development. Cre- 

 tinism in Switzerland and northern Italy is being controlled 

 by making sure that children have a suitable amount of iodin 

 in their diet. 



Defective infants appear from time to time among all 

 races of mankind. Some develop into so-called Mongoloid 

 idiots or dwarfs. These are usually undersized, rather infantile 

 in their bodily proportions, with pudgy rather than well de- 

 fined features, and with arrested development generally. It is 

 impossible to account for the appearance of such a defective 

 individual in a family that seems otherwise quite normal. 

 There seems, however, to be a definite causal connection be- 

 tween defects in certain structures and the abnormal de- 

 velopment of the individual. The Mongoloid idiot type is 

 apparently the result of a faulty development of the thyroid 

 and of the pituitary gland, a structure found at the base of 

 the brain. Considerable success has attended the treatment 

 of such dwarfs with extracts of the pituitary and of the 

 thyroid glands. But we are still in the dark as to what makes 

 the pituitary go wrong, just as we are as to what makes the 

 individual develop " right." 



Physiological Y aviation 



There is an apparent correlation between physical de- 

 velopment and the endocrine glands on the one hand, and 

 between the physical constitution and physiological charac- 

 ters on the other. In addition, there is the very clear evidence 

 that the so-called races differ among each other in important 

 functional traits. It has long been known, for example, 

 that dark-skinned races are very much more susceptible 

 to such diseases as measles and tuberculosis than are the 

 whites. On the other hand, yellow fever and hook-worm 

 are much more destructive among whites than among 

 blacks. 



