Action of Radium and X-Rays upon Tumour Growth. 131 



following lines. About the fourth day after inoculation of a graft, when the 

 tumour was palpable, the radium capsule was held on it for a certain length 

 of time. The minimum time of exposure necessary to prevent growth of the 

 tumour was found; it was not appreciably different from the exposure 

 required if the tumour material was removed from the body, given its dose of 

 radiation and re-inoculated into susceptible animals in the manner described 

 in Section A. The results were analogous indeed to those given in Table I 

 to the extent of showing that a small dose of radiation given to the tumour, 

 increased rather than hindered its growth. 



With the tumour in the animal, these exposures to small quantities of 

 radiation may be repeated in a wtiy not possible when the tumour is 

 irradiated outside the body. 



In the next series of experiments, the rats were inoculated on each side, 

 four days later all the tumours on the right sides were exposed to the radium 

 for times varying from ten minutes to twelve seconds ; these doses were given 

 once a week, their effect upon the growth of the tumour is seen in Table IV. 



Table IV. 



Conditions of irradiation 

 of tumour in animal. 



Volume of irradiated tumours com- 

 pared with the volume of controls 

 in the same animal. 



Remarks. 





1 week. 



2 weeks. 



3 weeks. 



4 weeks. 





15 rats, 10 minutes' exposure 

 to beta-rays once a week 



0-59 



0-43 



0-42 



0-44 



In 13 rats the control 

 tumour was the larger. 



15 rats, 5 minutes' exposure 

 to beta-rays once a week 



0-92 



0-76 



0-76 



0-85 



In 13 rats the control 

 tumour was the larger. 



19 rats, 1 minute's exposure 

 to beta-rays once a week 



0-98 



1 -07 



1 -25 



1-41 



In 14 rats the irradiated 

 tumour was the larger. 



17 rats, 12 seconds' exposure 

 to beta-rays once a week 



1 -14 



1-28 



1-33 



1 -46 



In 10 rats the irradiated 

 tumour was the larger; 

 in 5 rats the control ; 

 and in 2, both tumours 

 were the same size. 



The general trend of these observations is that, while a weekly exposure of 

 ten or five minutes checks the tumour growth, a reduction to one minute or 

 less has an opposite tendency. The beta-rays used were those from the 

 capsule employed in the experiment detailed under Section A (Table I). 

 The results show that a dose of radiation of about one-fiftieth of the lethal 

 dose (thirty-five or forty minutes, vide Table I), has, if anything, an 

 accelerating effect upon tumour growth. 



