Action of Radium and X-Rays upon Tumour Growth. 129' 



Table II. 



Number of 

 X-rayed animals. 



Exposure to X-rays. 



Effect upon body weiglifc. 



16 



1 minute daily for 9 -weeks 



Besulf : 25 per cent, diminution below 

 normal rate of growth in 63 days. 

 (All but 4 died.) 



22 



12 seconds daily for 8 weeks 



Result : 15 per cent, increase above- 

 normal rate of growth, in 62 days. 



21 



12 seconds daily for 4 weeks 



Result : 7 "5 per cent, increase above 

 normal rate of growth in 50 days. 



23 



2 seconds daily for 9 weeks 



Result : 10 Tper cent, increase above 

 normal rate of growth in 69 days. 



(2) Resistance to Subsequent Inoculations of Malignant Cells. — It has been 

 recorded (4) that rats exposed to small daily doses of X-rays before inoculation, 

 were found to have a greater resistance to the growth of sarcoma than normal 

 rats. This immunity was not absolute, for many of the rats grew tu.mours, 

 though smaller ones than the controls. Further experiments have been 

 carried out to determine whether complete immunity could be produced by 

 varying the period over which the irradiation was continued, the actual daily 

 dose of 12 seconds being unaltered. 



The data in Table III show the rate of growth of Jensen's rat sarcoma in 

 animals treated in this way. In all cases in which rats have been previously 

 submitted to X-rays the tumours grow at a slower average rate than in the 

 normal animal. It has not been found possible to confer an absolute 

 degree of immunity in this way, but it should be mentioned that we are- 

 dealing with a very rapidly growing tumour, one that doubles its volume in 

 less than four days. 



It appears from these results that the most prolonged time of irradiation, 

 does not give the highest degree of immunity. 



In contrast with this increase in the resistance of the susceptible animal 

 we have the experiments of Murphy and Morton (5), of Mottram and 

 Euss (6), and of Prime (7), who showed that, after a very large dose of 

 X-rays, an immune animal becomes temporarily susceptible to carcinoma and 

 sarcoma inoculations. 



The effect of a single rather large dose of X-rays in increasing the 

 susceptibility of the animal to inoculation has also been shown by the^ 

 authors (1), in the propagation of a spontaneous rat carcinoma. 



