[Tumour induction by methylnitrosourea in clawed frogs (Xenopus laevis) (author's transl)]

15 clawed frogs were bathed 12 to 17 times in solutions of 2 mg methylnitrosourea, dissolved in 1000 ml destilled water. 7 frogs developed tumours 8 to 22 months after starting the experiments. Another frog died of polycystic kidneys. The tumours were adenocarcinomas of the kidneys, sarcomas and a benign papilloma of the pelvis of the left kidney. A sarcoma of the soft tissues of the head showed an excessive granular storage of acid mucopolysaccharides in the cytoplasma of many tumour cells. Tumours of the nervous system did not occur.