230 LIFE: ITS NATURE AND ORIGIN 



cer. The compounds dimethylaminoazobenzene (butter yellow) 

 and o-aminoazotoluene can produce liver and bladder cancers in 

 rats if given orally or subcutaneously, and 3,4,5,6-dibenzcar- 

 bazole (made by hydrogenating and condensing two molecules of 

 beta-naphthylamine) causes proliferation of the gall ducts in mice. 

 Seamen exposed to tar and to insolation, as well as sufferers from 

 x-ray and radium "burns" are apt to develop cancer, though care- 

 fully regulated x-rays of certain wave length and intensity are now 

 used in attacking cancers. 



When butter yellow is fed to rats, biotin favors tumor forma- 

 tion, whereas riboflavin and allied vitamins oppose the carcino- 

 genic effects of this azo dyestuff. 30 These findings are understand- 

 able on the view that biotin favors or contributes to the formation 

 of a new, reproducible catalyst area in what becomes a cancerous 

 cell, whereas selective adsorption of the vitamin material blocks 

 this development. A somewhat analogous case exists in the antag- 

 onism between the sulfa drugs and p-aminobenzoic acid (PABA), 

 later referred to in this chapter. The relations between PABA, 

 inositol and pantothenic acid, in affecting the graying of the hair 

 of black rats, are curious and devious. According to G. J. Martin 31 

 the absolute amount of PABA is not the important factor in this 

 syndrome, but its ratio to pantothenic acid, which dominates the 

 vitamin-synthesizing powers of the gastrointestinal flora in the 

 rats. 32 



In 1915 Yamagawa and Ichikawa 33 produced cancers in the ears 

 of rabbits by continued application of certain tars. In the valua- 

 ble book 34 by Prof. Louis F. Fieser of Harvard University there 

 is reviewed the fascinating story of the team-work of chemists, 

 physicists, physiologists and others, which led to the isolation, 

 from carcinogenic tar, of a previously unknown but potently ac- 

 tive hydrocarbon, 3,4-benzpyrene, although it was present only 

 to the extent of about 0.003 per cent. Synthetic 3,4-benzpyrene, 

 prepared after its structure was clarified, is identical in its action 

 with that obtained from tar. A few details of this important de- 

 velopment may be mentioned. High-boiling tar fractions proved 

 to be non-carcinogenic; but I. Hieger 35 observed that active tars 

 and oils gave a characteristic fluorescence spectrum, with bands 

 at 4,000, 4,180, and 4,400 A. Since 1,2-benzanthracene was found 

 to give similiar bands, J. W. Cook prepared a large number of al- 

 lied compounds, among which 1,2,5,6-dibenzanthracene proved 

 to be actively carcinogenic — the first pure substance of known 



