Among the various problems of cancer research the question of the experimental production of cancer has been brought into the foreground in the last decade. The pioneer work in this field has been done by Fibiger1–3 who in 1914 published reports of his experiments with rats, in whose stomach he succeeded in producing cancer by feeding the animals with cockroaches infected with a roundworm Spiroptera neoplastica (Gongylonema neoplasticum).A great interest in the subject of experimental cancer production was elicited by Yamagiwa and Ichikawa,4–9 who in 1915 reported successful results of production of folliculoepithelioma in rabbits by prolonged application of coal tar to rabbits' ears, after futile attempts by many investigators, Cazin,10 Hanau,11 Jores,12 Brosch,13 and Bayon,14 to employ coal tar for production of cancer.The experiments of Yamagiwa and Ichikawa were repeated on mice in 1918,15 by Tsutsui, and more recently by Fibiger and Bang,16–19 Roussy,20 Deelman,21 Bierich,22–23 Russell,24 Murray and Woglom,25 Bloch and Dreifuss,26–27 Jordan,28 Roffo,29 Burckhardt and Müller,30 and many others. The possibility of voluntary production of blastomata was thus established.Some investigators, as Bloch, Jordan, etc., started experimenting with different fractions of distillation of coal tar in order to find in the complicated mixture represented by coal tar, a chemically well defined substance which possesses the ability to produce cancer. Leitch31 used crude shale oil in producing tumor formations. Applications of potassium arsenite by Leitch and Henneway32 led to formation of a growing tumor in one mouse. Cancer was produced by Passey33 by means of soot mixed with quicklime. Stahr34 succeeded in producing epithelioma on the tongue of rats by feeding them with oats. Bullock and Curtis35 induced formation of sarcoma in the liver of rats through mediation of Cysticercus fasciolaris, the larval stage of Taenia crassicollis of the cat. Infestation of the rat by the larvae follows the ingestion by the rat of the food contaminated with cat feces containing the eggs of this tapeworm.