The Rapid Production of Tumours by Two New Hydrocarbons *

(a) Sarcoma: Maisin and Coolen8 obtained a rapidly growing sarcoma in a rat 25 days after one subcutaneous injection of 3:4benzpyrene (1 mg. in lard). Valade"3 found "un petit sarcome peritracheal" on the 25th day in a rat which had received 5 intratracheal injections, each of 0.2 mg., of methylcholanthrene in arachis oil. Dr. L. D. Parsons at the Royal Cancer Hospital induced a sarcoma in a mouse in 22 days during which 11 subcutaneous injections of 0.25 cc. of 0.4 per cent sodium-1:2:5:6-dibenzanthracene9:10-endo-a4-succinate in saline were given (unpublished observations). (b) Papilloma and Epithelioma of Skin: Maisin and Liegeois' observed the first papillomas of the skin in 30 days in mice to which 3:4-benzpyrene (1 per cent in benzene) was applied twice weekly, while the 69th day was the first upon which "le cancer pouvait etre diagnostique avec une certitude complete." In our own experiments' a papilloma was obtained in 31 days in one of a series of mice to which methylcholanthrene (0.3 per cent in benzene) was applied. Apparently the shortest recorded time in which a malignant tumour of the skin of the mouse has been produced is 8 weeks