1180 RADIATION BIOLOGY 



nately, no controls were observed. Lorenz (1944) injected eleven mice of 

 a lung tumor-susceptible stock four times at weekly intervals with an 

 aqueous radon solution totaling 1.2 mc. Some animals lived up to eight 

 and one-half months, but no increase in lung tumor incidence was 

 observed in the injected animals over that of controls. Rajewsky et al. 

 (1943) exposed mice continuously to various doses of radon in an emana- 

 torium. Mice exposed to 1.16 X 10~ 6 curie per liter lived from 161 to 

 453 days. Of the twelve experimental animals, ten had adenomas of the 

 lung, one an adenocarcinoma originating from a small bronchus, while 

 only one of the control animals had an adenoma. 



Thus it is questionable whether radon can induce lung tumors in 

 experimental animals. The work of Rajewsky et al. suggests this, but a 

 problem as important as this deserves a sounder experimental foundation. 



Experimental Induction of Lung Tumors by X or Gamma Radiation. 

 This has been carried out on a much larger scale. The induction rate of 

 lung tumors in mice by total-body irradiation is very low and the tumor 

 development time is long. 



Furth and Furth (1936) gave evidence that massive doses of X radia- 

 tion given to three strains of lung tumor-susceptible mice induces lung 

 tumors. The increase in lung tumor incidence observed in females was 

 slight but statistically significant. Lorenz et al. (1946) exposed mice to 

 chronic y radiation giving 8.8 r daily (8 hours) and a total of approxi- 

 mately 2400 r over a period of ten months and found an increase in lung 

 tumor incidence of 50 per cent over controls. In later experiments, 

 Lorenz (unpublished data) has shown that the lung tumors are induced 

 by a direct action of the radiation upon the lungs. The lung tumors 

 induced in mice were alveolar in origin and benign, as were those in the 

 controls. 



Lisco and Finkel (1949) induced bronchiogenic carcinomas in rats by 

 inhalation of an unknown quantity of radioactive cerium oxide; this 

 compound covers the bronchi tenaciously. 



Gorbman (1949) described the development of tumors of the trachea in 

 mice that had been injected with large doses of I 131 . This was not seen 

 by one of us in more than thirty mice of the same strain similarly radio- 

 thyroidectomized by I 131 and observed for over a year. The changes 

 seen in the trachea were destructive and proliferative but not neoplastic. 

 Cancer of the larynx was described in a woman whose thyroid received 

 prolonged X radiation (Jacques, 1935). 



BONE 



The development of a malignant tumor in a normal bone or in a benign 

 tumor that had been exposed to heavy doses of X or y radiation was first 

 described by Beck in 1922, and in 1945 Hatcher could collect from the 



