SELECTIVE ELIMINATION AS A FACTOR IN INCREASING THE 

 IMMUNITY OF POPULATIONS 



CHARLES HERRMAN 



New York 



"Nature is beneficent-life giving — but also ruthlessly destructive. Its 

 eternal shower of blessings has not effaced or even dimmed the edict that 

 only the fit shall survive." — M. Luckiesh. 



In his presidential address before the American Pediatric Society in 1923, 

 Holt (1) discussing the reduction in the mortality in infancy and 

 childhood in New York City said, "However we may speculate as to the true 

 explanation, the fact remains that we are witnessing a remarkable reduction 

 in mortality in infancy and childhood. We should all like to consider this 

 as a result of the advance in preventive medicine and in hygiene, and un- 

 doubtedly much of it is due to these causes, but there remains a large factor 

 for which as yet we cannot satisfactorily account. " In a paper (2) published 

 shortly after, I suggested that the explanation was to be found in the action 

 of selection, the most susceptible infants and children succumb and are 

 eliminated as possible parents, the survivors more resistant transmit this 

 advantage to their offspring so that fewer deaths occur. I also emphasized 

 the fact that in large centers of population with their great congestion con- 

 tact infection was more common, so that such a selective elimination would 

 occur with greater certainty and at an earlier age. In families in which in 

 addition to an infant there are older children who attend school and mingle 

 freely with other children the common communicable diseases of childhood 

 can be introduced into the home, so that even young infants may be infected. 

 Children of preschool age may be infected in nurseries or kindergartens, in 

 institutions for the care of infants and young children, or in the wards or 

 out-patient department of hospitals. 



At the outset it is important to distinguish between good health as judged 

 by the state of nutrition or muscular development, and resistance to the 

 specific infectious diseases. Nothing in the general appearance is a certain 

 indicator of adequate immunity reactions. These are dependent on heredi- 

 tary factors, although they can be modified by the character of the feeding 

 and hygiene. The hereditary factors have been studied most carefully in 

 diphtheria in which by means of the Schick reaction we have a simple 



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