1186 



RADIATION BIOLOGY 



the specific ionization may be important. Brues (1949) found that the 

 development period of bone tumors is comparable in mice, rats, rabbits, 

 and dogs. His findings are illustrated in Fig. 18-1. The ordinate repre- 

 sents the probability that a mouse in a given dosage group will develop a 

 tumor or possess it in a microscopic state on a given day. 



Species differences doubtless exist, as illustrated by leukemia and 

 ovarian tumor induction in mice, and difficulties of their induction in 

 other species of animals; however, not enough work has been done in 

 other species and the tumor development time may not have been given 

 adequate consideration. The species differences are probably the same 

 for all types of carcinogens, e.g., leukemias are readily induced in mice 



0.020 



0015 - 



0010 



0005 



100 200 300 400 500 600 700 800 

 DAYS 

 Fig. 18-10. The relation of dose of Sr 89 to rate of induction and latency period of bone 

 tumors {after Brues, 1949). 



also by chemical carcinogens and hormones, but not in other species. 

 Work in this area is, however, inadequate. 



Cocarcinogenesis by Irradiation. Many observations made on the 

 induction of neoplasms in man or animals subjected to ionizing irradia- 

 tion are best explained by postulating cofactors as being operative, before, 

 during, or after irradiation. 



Observations made in the course of therapeutic use of X radiation in 

 the control of chronic inflammatory lesions in man induced Lacassagne 

 and Vinzent (1929) to study the promoting factor of inflammation in 

 carcinogenesis. In a series of studies, Lacassagne et at. (1927-1933) have 

 conclusively demonstrated that, in the course of inflammation, many 

 types of cells are potentiated to the carcinogenic effects of X radiation. 

 Streptobacillus caviae introduced into the thigh of the rabbit produced a 

 suppurative inflammation which was often fatal but could be cured by 

 X radiation. From six months to four years later infiltrative metastasiz- 

 ing neoplasms appeared in several rabbits so treated. Two malignant 

 tumors (an osteoblastoma and a fibromyosarcoma) were obtained in the 

 pectoral region of rabbits in which abscess was produced with diatomace- 



