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THE CARCINOGENIC STIMULUS 



Fig. 9. Ovarian tumor (t) developing in an X-irradiated ovary transplanted to a normal 

 male of the same inbred strain. If such ovaries are transplanted to females, ovarian tumors 

 •do not develop, indicating that ovarian secretion suppresses tumorigenesis either directly, 

 or indirectly via the pituitary gland. 



Fig. ID. Ovarian tumor (t) developing in an ovary transplanted to the spleen of an other- 

 wise ovariectomized mouse. 



Fig. 1 1 . Hormonal influence on X-ray induced ovarian tumors of mice. The tumor on the 

 left was induced when one ovary was irradiated with 200 r and the second ovary removed. 

 The small ovary on the right is one which was irradiated with the same dose of X-rays, the 

 second ovary (in the middle) remaining functional. 



Fig. 12. Irradiation of a single mouse ovary with the second ovary remaining functional. 

 As illustrated in Fig. 1 1, here again irradiation of a single ovary was not tumorigenic if the 



Legends conliinied on p. Ssg 



