126 Drs. S. Kuss, H, Chambers, and Miss G. M. Scott. 



rat sarcoma (F. 16), for which we are indebted to Dr. J. A. Murray, the 

 Director of the Imperial Cancer Research Fund ; and a rat carcinoma, which 

 occurred as a spontaneous tumour in these laboratories in January, 1919, 

 and which has been described (1) to the Pathological Society of Great Britain 

 and Ireland, March, 1920. Most of the work has been done with Jensen's 

 rat sarcoma, and, except where otherwise stated, the observations refer to 

 this tumour, 



(A) The Efed of Bays in Various Doses %ipon Malignant Cells. 



A dose of X-rays or radium rays can be given most accurately tO' 

 malignant cells when the tumour is not in the animal body. The method 

 we have adopted since 1912 (Wedd and Euss, 2) has been to excise a 

 tumour, cut a slice of it, and expose this aseptically to radiation for any 

 length of time desired ; the tumour cells are then implanted into normal 

 rats, and the size of the subsequent growth is accurately recorded. It is- 

 more convenient in this type of experiment to use the beta-rays from radium 

 than X-rays, for, however carefully the X-rays may be controlled, there is 

 much more likely to be a change in the radiating power of the source than if 

 radium is used. • 



Table I shows the results which are obtained when the cells of Jensen's 

 rat sarcoma, before being inoculated into normal animals, receives exposures 

 ranging from forty minutes down to twelve seconds. The last column 

 compares the size of the irradiated with the non-irradiated tumour in the same 

 animal ; the inoculations were made in the right and left axillse. The source 

 of the rays used was a capsule containing 20 mgrm. of radium bromide- 

 (Ea.Br2.2H2O), spread over an area of 4 sq. cm., and covered with a thin 

 layer of varnish ; the varnish absorbs alpha- and soft beta-rays. 



Table I. 



Time of 

 exposure to 

 radium. 



Number of rats in 

 ■whicli the irradiated 

 tumours did not grow. 



Number of rats in 

 which the irradiated 

 tumours did grow. 



Yolume of growth 

 compared with control 

 3-4 weeks after 

 inoculation. 





12 







35 „ 



11 



1 



0-07 



30 „ 



13 



5 



0-29 



10 „ 





6 



0-44 



5 „ 





6 



0-85 



1 minute 





8 



0-82 







8 



1-35 



The conclusion drawn from this series is that, as the dose of rays given to 

 the sarcoma cells diminishes from a lethal dose, a gradual change is observed. 



