The effect of a water-soluble carcinogen on the early development of the frog.

Experimental carcinogenesis, or the experimental production of tumors in animals, is a relatively new field of research. Its beginning dates from 1915 when the Japanese workers Yamagiwa and Itchikawa first succeeded in producing papillomas and true malignant growths on the ears of rabbits after continued application of tar. This important observation at once raised the question as to the nature of the component or components in tar which were responsible for its carcinogenicity. The English workers, Kennaway, Cook and their associates, attacking the problem with this question in mind, finally succeeded in isolating 3,4-Benzpyrene which is now recognized as the active agent in coal tar. [...] In brief, we have reared frogs’ eggs in solutions of a water-soluble carcinogen, the hope being that we could observe changes in the living cells which it is difficult to do in work with larger animals such as mice. Our procedure also appeared to offer some possibilities not available in tissue culture work or in work with small free-living organisms. Specifically, in the frog embryo certain fundamental developmental processes are taking place, and thus opportunity is afforded to observe the effect of the carcinogen on an actively growing and differentiating system