PHYSICAL FACTORS IN RACE SURVIVAL 293 



ticular infection that was responsible for the decline of the Maya race, 

 although that may be a possibility. 



The immunologist has three great tasks before him. One is to fortify 

 and relieve individuals who are menaced or attacked by an infection. A 

 second is to eradicate and eliminate the occurrence of infections where that 

 is possible; but this can only be permanently accomplished by exterminating 

 the organism that causes them, otherwise they return upon the least relaxa- 

 tion of vigilance. The third and most important task of all is to build up 

 the general resistance of the race. And this is the greatest, and possibly 

 the only permanent, benefit that the immunologist can confer upon the race. 



Now there is one most effective means of building up immunity to inter- 

 current infections, as well as of eradicating hereditary weaknesses, namely 

 by the interbreeding of those who possess high immunity, and who are 

 wholly free from such hereditary tendencies. We know for one thing that 

 it is possible by such means to breed a race of mice that is entirely immune 

 to cancer, whereas other breeds of mice will be susceptible to it. We also 

 know that it is possible to establish immunity to particular diseases in plant 

 strains by the interbreeding of strains that are found to be immune. Hence 

 through the interbreeding of individuals who are highly immune, and free 

 from pathological stigmata, we may attain high immunity to inter- 

 current infections and a great measure of freedom from hereditary weak- 

 nesses. Through breeding between those of high immunity and those of 

 poor immunity, these tendencies will recur in a certain incidence. And 

 through the interbreeding of individuals of poor immunity, or hereditary 

 predisposition, we can anticipate an inevitably high incidence of such 

 tendencies. 



We are compelled to recognize that medical science, in its humanitarian 

 purpose, preserves in many instances individuals who, under the normal 

 biological process of natural selection would be eliminated and cease to be a 

 source of weakness to the race. But surely medical science should take 

 some thought that such racially weakening influences be not perpetuated. 

 We do not maintain that medical science need relax its efforts to prevent 

 disease, to ameliorate suffering, and to save human life, provided that it at 

 the same time seeks effective means of improving the general quality and 

 resistance of the race. But if medical measures, however immediately effec- 

 tive they may be, only succeed in lowering the general resistance and racial 

 vitality by preserving weaker breeding strains, which in turn will reproduce 

 and perpetuate their physical weaknesses, we cannot regard such measures 

 as contributory to the ultimate improvement of a race, or to its survival. 

 Indeed it only raises the possibility of an eventual racial cataclysm in a weak- 



