Smoking and Cancer--in Dogs

Cigarette tar painted on the backs of mice has long been known to produce cancer, but until now there has been no proof that lung cancer of the human type could be induced in any animal by forcing it to smoke. Thus, said the tobacco industry, there was no evidence that cigarette smoking caused lung cancer. The fact that heavy smokers are 20 times as likely to die of lung cancer as nonsmokers, said its spokesmen, was merely a "statistical association" that did not prove a cause-and-effect relationship.

Last week, in the hope of demolishing that argument, American Cancer Society researchers reported that of 36 beagles they had trained to smoke heavily, twelve had developed lung cancer. The cancer victims had smoked seven to nine unfiltered cigarettes a day over a 21-year period. That, Dr. E. Cuyler Hammond figured, was the equivalent of a man's smoking almost two packs a day for 18 years, after making allowance for the beagles' size and shorter life span. Two of the dogs' cancers were indistinguishable from human smokers' lung cancer; the remaining ten were of types that are less common but are also found in men. There were other significant results: dogs that smoked the same number of filtered cigarettes did not develop cancer. Nor did those that smoked an average of 31 non-filter cigarettes daily.

Like Teen-Agers. Previous attempts to reproduce the effects of human smoking in the laboratory had failed because animals could not be taught to inhale. At Manhattan's Sloan-Kettering Institute, Dr. William G. Cahan devised an ingenious method of inserting a plastic tube through an opening in a beagle's windpipe and pumping in smoke drawn from cigarettes. The animals were harnessed in an open box and, after a few weeks of gradual conditioning (at first, many coughed and retched like teen-agers with their first drags), showed signs of addiction. They inhaled voluntarily and appeared to enjoy smoking. Cahan's tests produced emphysema but no cancers in dogs. Dr. Oscar Auerbach used the same method with more dogs for a longer period.

Cancer Society spokesmen cautioned that the filter cigarette cannot "objectively be called a 'safe' cigarette" simply because the dogs kept on filter cigarettes did not develop cancer. But they conceded that with the filters, damage to lung tissue advances less rapidly. While animal experiments can never offer conclusive proof about disease in man, Auerbach has previously shown that human lungs undergo similar, progressive changes in proportion to the amount smoked. This, coupled with his beagle findings, makes an undeniably strong case.

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