86o 



THE CARCINOGENIC STIMULUS 



I I 



Fig. 56. Section of rhabdomyosarcoma induced by administration of peanut oil subcuta- 

 neously. Presumably this oil which is used as a vehicle for carcinogenic agents is not tumor- 

 inciting. However, since a certain number of neoplasms are induced by "non-carcinogenic" 

 agent, either carcinogenic action is non-specific, or various materials contain carcinogens. 

 X 250 



Fig. 57. Section of fibrosarcoma induced by the injection of methylcholanthrene in peanut 

 oil into a mouse. Numerous mitotic figures present. X 200 



Fig. 58. Multiple pulmonary tumors in section of lung of a mouse fed methylcholanthrene. 

 X 30 



-f^'g- 59- Section of epithelial neoplasm induced in the skin of a mouse by painting with 

 methylcholanthrene. The arrangement of neoplastic cells simulates that seen in human 

 basal cell carcinoma. X 45 



