THE CUE Ml ST UY OF TUMORfi 493 



stance has yet. been isolated from or detected in malignant growths 

 that is peculiai- to lliem and not found in normal cells, and still less 

 has any substance been detected that accounts in any way either 

 for the occurrence of tumors or for tlie effects that they produce. 



Tumor cells seem to depend upon much the same conditions as nor- 

 mal body cells for their growth, since anything that leads to wasting, 

 malnutrition, or atrophy in the tissues of the host usually tends to 

 impede the rate of growth of the tumor cells, in marked contrast to 

 infectious diseases. Specific attempts to modify tumor growths by 

 diets (Mendel-Osborne diet) which stunt the animals because lack- 

 ing certain amino-acids necessary for growth, have been successful,-'' 

 but it is dilBcult to be sure that this effect depends on the specific ab- 

 sence of a definite substance rather than on general malnutrition.-*' 

 Tumor cells made incapable of utilizing carbohydrate through com- 

 plete phlorizin diabetes -'^ may be unable to grow, and even retro- 

 gress completely. Furthermore, the constituents of the hypophysis 

 that stimulate somatic tissue growth also stimulate growth of tumor 

 tissues.-'' 



The discovery by B. Fischer^ that fat stained with scarlet-R and 

 injected beneath the skin causes epithelial proliferation resembling 

 but not terminating in cancer, has led to much speculation as to the 

 nature of substances which might cause cells to proliferate lawlessly 

 and malignantly. The great frequency of cancer in workers in prod- 

 ucts of destructive distillation of wood (tar, soot, paraffin *) has 

 also indicated the possibility of chemical stimuli causing cancers. A 

 striking instance of chemical stimulation causing cancer formation 

 is furnished by the cases of carcinoma of the urinary bladder, which 

 is a common cause of death in men who work in aniline dyes, both 

 dyers and dye makers being subject to this condition. The dyes that 

 seem to be responsible belong to the group of aromatic amido-hy- 

 droxyls, including safranin, congo-red, benzopurpurin, fuchsin, eosin 

 and others.'^ H. C. Ross " has made extensive studies of the relation 

 to cancer of substances which cause leucocytes to multiply, designat- 

 ing them as "auxetics." These seem to be present in the anthracene 

 fractions of tar,""" which may explain the frequency of cancer in work- 

 ers in tar, soot and paraffin. Japanese investigators report that pro- 

 tracted irritation of rabbits' ears with tar leads to strikingly infiltra- 



2a See Sweet, et a1., Jour. Biol. Cliem., 191.5 (21), .300. 



2b -Rous. .Tour. Exp. Med., 1914 (20), 4.3.3. 



2c Benedict and Lewis, Proc. Soe. Exp. Biol.. 1914 (11) 134. 



2d Robertson and Burnett, Jour. Exp. Mod., 1916 (23), 631. 



3 Verb. Dent. Path. HeselL, 1906 (10). 20; see also TTasra. Zcit. Krehsforscli.. 

 1913 (12), .52.5: Saelis, Wien. klin. Wocli., 1911 (24), 1.5r)l: Stoe])pr, Muncli. 

 nied. Woch., 1910 (57). 7.39 and 947. 



•tSee Bavon, Laneet. 1912 (ii), 1579. 

 - 5 See Leiienberffer, Beitr. klin. Chir.. 1912 (SO), 208, 



6 "Researches into Induced Cell Reproduction and Cancer," London. 



eaNorris, Biocliem. Jour., 1914 (8), 253. 



