That arsenic may cause keratoses is not a particularly unfamiliar fact, but it has been within the past few years that it has become generally recognized that the internal administration of that drug can cause keratoses that may eventuate in carcinomata. These lesions have been carefully studied by Hartzell,I= Schamberg,* and Fordyce,* all of whom agree on the essential points. Arsenic must be administered over a considerable length of time, and in fairly largo amounts. Typical keratoses appear which have a histology that is essentially the same as those already described. The cancers are prickle celled ones.

" )lnrt** U: Amir. Jour. Med. Sclen.. 1897. cxvlii. 205.

Solminbcrg: Jour. Cutan. Dls.. 1907. xxv. 26. "Fordyce: Amrr. Jour. Med. Scion . 1910. Iv. 1624.