There are thus 5 different species of laboratory animals
with common ndings that are not consistent with the epidemiological
results in smokers. Some possible reasons for
this discrepancy were given in the rst paper, including the
ability of laboratory animals in general to predict human neoplastic
disease. However, the addition of 16 further representative
studies in 3 additional species adds weight to the
concept that the laboratory animals generally used to assess
carcinogenic potential in humans do not display evidence of
any such potential when treated by the inhalation route with
mainstream cigarette smoke.