9, 10-Dimethyl-1,2-Benzanthracene as a Highly Potent Carcinogen for the Rabbit's Skin*

There are many types of investigation connected with the tumor problem for which a large laboratory animal such as the rabbit would be more useful than a small one such as the mouse. For problems connected with experimental carcinogenesis the limiting factor is, naturally, the availability of a suitable carcinogen. Neither tar nor 3,4-benzpyrene can be considered as suitable for the rabbit: The objection to the former is that it is a complex mixture of varying composition, action, and toxicity; to the latter, that its action on the rabbit is very weak. As for the many other polycyclic hydrocarbons that are known to produce skin tumors in mice, few seem to have been tested on the skin of the rabbit (2). 1 Hence it is not possible to say from previous studies whether the rabbit can or cannot be extensively used for the detailed investigation of carcinogenesis. It has been established that for mouse skin the most potent of the known agents is 9,10-dimethyl1,2-benzanthracene (1, 3). It seemed desirable, therefore, to test this compound on the rabbit's skin also, and to compare the results with those obtained with tar and benzpyrene.