PHYSICAL FACTORS IN RACE SURVIVAL 291 



But there is still another important observation to be made in regard to 

 cancer. Myron Gordon of Cornell University, by properly controlled 

 scientific experiment, has been able to establish definitely that melanosis, a 

 true form of cancer, may be produced by cross-breeding certain varieties of 

 fish. This fact has also received confirmation in the occurrence of melanosis 

 in cross-breeding by fish-fanciers. To assume that such a principle should 

 not have any application in mammals or in the human species would be 

 against all biological experience. Hence in efforts to eliminate cancer or 

 other pathological stigmata from the human species, the whole subject of 

 cross-breeding would need to come under careful scrutiny. 



Thus it might seem that one of the most important fields of preventive 

 medicine, is in the study of pathological heredity, in order the better to 

 understand such heredity and to discover means by which this great cause 

 of disease could be diminished, and in some cases eliminated. Primitive 

 races have always been inclined to attribute the occurrence of disease to 

 inimical spiritual influences; they at least sought a primary cause, and tried 

 to ward off disease by propitiating the spirits. Perhaps it is not altogether 

 a mark of superior intelligence on the part of civilized individuals to assume 

 that the occurrence of disease in the human species is to be regarded as 

 largely casual and fortuitous. 



If individuals are free from inherited organic defects and weaknesses, the 

 only serious physical menace to their living out their normal term of life and 

 fulfilling their reproductive and other racial functions may be said to be the 

 intercurrence of infections. It has been known for a good while that such 

 infections are due to germ invasions. Medical science is now able in some 

 instances to combat with greater or less success the invading germ. But the 

 main defence against such invasions is the physiological immunizing function 

 of the human organism. It is possible that medical science may eventually 

 be able to eradicate some diseases. But it will be a very long time before 

 individual resistance will not constitute the main factor in defence against 

 disease and in the maintenance of health. It needs to be remembered that 

 in most cases medical science is wholly impotent to cure a disease without the 

 aid of the physiological resistance of the individual, and the degree and 

 extent of such resistance is inborn and hereditary. The greater this re- 

 sistance, the less invasion of disease there will be; and the successful or 

 unsuccessful treatment of disease depends again upon individual resistance. 



The constant menace of these germ enemies of a species is not to be under- 

 rated. There is good reason for thinking that they have at times been 

 responsible for the destruction not only of breeding groups but for that of 

 entire species. Professor Osborn is inclined to attribute the extinction of 



