Medicine: Cancer and Heredity

“The bulk of the evidence points to microparasites as the probable cause of sarcomas and carcinomas,” says Dr. Erwin F. Smith, chief plant pathologist of the U. S. Department of Agriculture, and Vice President of the American Association for Cancer Research.

It was Dr. Smith who demonstrated that the crown gall, a plant disease resembling animal cancer, could be experimentally transmissted from plant to plant by cultures of a microorganism found in the gall. He is convinced that human cancers are caused by a similar infection, though no active parasite, either bacterium or protozoon, has yet been found. Many investigators of plant and animal cancer have caused cancer experimentally in varied ways—by injecting a virus from the growths, by painting rats with irritating substances, and by nematodes (microscopic worms), tape worms, other parasites. In short, Dr. Smith’s theory is that at least some cancer is caused by the irritation of parasites acting upon organs unable to withstand it on account of inherited or acquired weakness. Physiologically injurious living as to eating, drinking, chewing, smoking, may prepare a suitable soil that easily succumbs to the parasitic inciting cause. This may be a long-continued process, not confined to old age, but merely making itself apparent then. Heredity alone cannot cause cancer but may provide a weakness susceptible to irritation.

The fact that cancer is not apparently contagious, that no microbe has been isolated, need not negate Dr. Smith’s theory. The parasites of syphilis, yellow fever, leprosy and many other diseases have beenisolated only within very recent years. Some diseases, like malaria, are not transmitted directly from person to person, but their parasites must spend some time in the body of an-other animal host.

These experiments and a vast multitude of others have so advanced our knowledge of cancer that we may hope for the full solution of the problem in the not distant future, says Dr. Smith. He pleads for financial support for responsible and detailed cancer research, rather than prizes attracting a flood of ” cancer cures.”