826 



THE CARCINOGENIC STIMULUS 



II 





Fig. 3. TSH secreting pituitary tumor (p) induced in C57BL mouse by administering radio- 

 iodine. The pituitary tumor developed as a response to the hypothyroid state. Latent period 

 of induction several months. 



rig. 4. Mouse bearing autonomous TSH-secreting pituitary tumor transplant (a). Initially 

 such pituitary tumors are transplantable only into hypothyroid hosts. Following several 

 transplants these pituitary tumors grow in intact animals. Their secretion stimulates the 

 normal thyroid gland (b) to hyperplastic activity. 



Fig. 5. Post-castrational adrenal cortical adenoma (a). The adrenal cortex of certain strains 

 of mice is susceptible, whereas in other strains the adrenal cortex resists the indviction of 

 such adenomas, x 50 



Fig. 6. Post-castrational adrenal cortical adenoma (a) with lipid-laden cells. Secretion of 

 sex steroid is associated with the appearance of these cells. X 56 



Legends continued on p. Ssy 



