PHYSICAL FACTORS IN RACE SURVIVAL 289 



prevalent. It need hardly be said the occurrence of goitre is now definitely 

 connected with a lack of iodine in the human system due to its absence in 

 drinking water and in food. Now all members of this community lived 

 under practically equal conditions of exposure to goitre; but it was found 

 that the incidence of goitre was largely confined to certain families in which 

 there was a history of cases in successive generations. In other families who 

 were equally exposed there was almost no record of goitre. It was also 

 discovered that in the families in which goitre frequently occurred there 

 was a marked tendency to deficiency of the thyroid function, to which the 

 goitre could be readily ascribed. Now thyroid deficiency can only be 

 attributed to a hereditary origin. Thus we might expect to find the occur- 

 rence of many diseases due indirectly, but none the less certainly, to a hered- 

 itary weakness in one direction or another. Further careful study promises 

 to make a similar clarification in the incidence of many diseases. 



Observation goes to show that the susceptibility to certain diseases is 

 often associated with particular physical characteristics, which are un- 

 questionably of hereditary origin. We may cite one of many instances. 

 In observations of infantile paralysis, Dr. George Draper found that it 

 affects more frequently children who are brunet, who have mongoloid eyes, 

 deeply pigmented skins, wide faces with widely separated eyes, irregular 

 teeth, and certain endocrine deficiencies. Indeed this might seem to 

 present a picture of physical racial disharmonies consequent upon race 

 crossing at some point in the ancestry. Dr. Draper says that "So far as the 

 paralytic symptoms of polyomyelitis are concerned, the type of child is more 

 important than the virus of the disease itself." And yet an assiduous 

 writer on population conditions, to whom biology must apparently be a 

 sealed book, can ask the question, "Of what practical use is a knowledge of 

 such things as skull measurement and eye color?" 



Innumerable instances could be assembled of the transmission from 

 parent to offspring of physical susceptibilities, predispositions, and idio- 

 syncracies. Many are able to trace such inherited traits in their own case, 

 and to observe that they manifest themselves under similar exciting causes, 

 are likely to occur at much the same age, and to follow much the same 

 course as in parents or other members of their family. Physicians con- 

 stantly encounter such histories, and life insurance companies long ago 

 learned to take account of them. They may not always be a matter of 

 serious consequence, but they go to indicate in many instances the inheri- 

 tance of physical weaknesses in what can only be inferred to be somatic 

 physical patterns that are closely identical. 



To illustrate the causation connection of closely identical somatic phys- 



