The effect of aristolochic acid on the development of methyl-cholanthrene tumours in mice.

1. In several experiments on groups of mice aristolochic acid administered by mouth reduced the induction rate of methyl-cholanthrene tumours. 2. In cases where such tumours were influenced their growth was slowed down. 3. If aristolochic acid treatment is started a long time after the methylcholanthrene injection its effect on carcinogenesis is weaker. 4. Oral administration gave better results than injection. 5. Pertussis vaccine seems to have no significant influence on tumour development.