554 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



cover without any permanent ill effects. It is surely not unjusti- 

 fiable to consider that similar differences of vulnerability may exist 

 in the case of the germ plasm. Adverse factors of the environment 

 will then not be operative upon the germ plasm of the whole com- 

 munity, but only upon that of the susceptible portion ; and it will no 

 more follow that " all races affected by any sort of disease should 

 drift steadily toward extinction " than it follows that all persons af- 

 fected with tuberculosis, influenza, or other disease will necessarily 

 die of those complaints. Further, not only may some germ plasm be 

 practically immune, but plasm which is susceptible may be influenced 

 to varying extent, both quantitatively and qualitatively, thereby giv- 

 ing rise to many different forms of variation and degrees of de- 

 generacy. 



As a matter of fact this is precisely what happens; and the mani- 

 festations of degeneracy as seen in daily life vary within very wide 

 limits. In some instances the variation is so pronounced as to inter- 

 fere seriously with the survival value of the resulting offspring. 

 Such individuals will then be eliminated by natural selection, pro- 

 vided this is sufficiently rigorous, so that, far from being subversive 

 of the doctrine of evolution, the process is one which actually con- 

 duces to racial evolution. It may happen, however, that the varia- 

 tion is much less pronounced and the social environment not suffi- 

 ciently rigorous to bring about elimination. Such individuals will 

 then not only be enabled to survive, but will intermarry with those 

 whose germ plasm is unimpaired, with the result that a dilution of 

 the morbid process may take place so far as individual members are 

 concerned, but there w T ill be a more widespread dissemination 

 throughout the community. 



As will presently be shown, these milder manifestations of degen- 

 eracy occur more particularly in the central nervous system. They 

 involve those parts of the nervous system concerned with the higher 

 processes of mind, and they take the form of a diminished mental 

 potentiality, a lessened vigor and initiative, a want of balance, and 

 a loss of control. The social expression of these changes is seen in an 

 incapacity of the community for sound government and legislation, 

 for organization and for social progress, and an inability to compete 

 with more vigorous neighbors, both in the arts of peace and in those 

 of war, the natural termination of which is social decline or even dis- 

 ruption. It is exceedingly questionable if any student of history will 

 be found to maintain that there is not " an iota of evidence" of the 

 past existence of such degeneracy. 



As to why the germ plasm of different individuals should vary 

 in susceptibility to the action of adverse factors in the environment, 

 we know very little. It is not inconceivable, indeed it is a reason- 

 able assumption, that its state of nutrition may be subject to change, 



