486 Drs. Russ and Chambers. Action of Radium [Mar. 14, 



Of the five remaining animals in Series III one died, the growths in two 

 of the rats disappeared in 30 and 38 days, the animals proving refractory to 

 subsequent inoculation. The nodules in the two remaining were palpable for 

 116 days, when they were excised and found to consist of fibrous tissue. 



To attempt to interpret the course of events illustrated in figs. 2 and 3 two 

 alternatives may be considered. 



If it be supposed that all of the irradiated cells suffer some damage 

 dependent upon their time of exposure, then the irradiated series might be 

 expected to show a general quantitative sequence, and this appears to be the 

 case. On these lines the tumour cells appear to overcome the effect of their 

 irradiation after a prolonged period in the animal body. 



On the other hand if it be supposed that some cells are unaffected by the 

 rays, the delay in the apparent onset of growth would be proportional to the 

 time of exposure, and would depend on the number of cells left undamaged. 



Although the observations do not allow of a decision between the alterna- 

 tives, they show that the irradiated cells increase at a slower rate than do 

 the controls. The areas of the tumours were found by actual measurement, 

 and if these areas are raised to the three halves power, numbers are obtained 

 which are proportional to the volumes of the tumours. On the simplest 

 assumption of continuous cell proliferation and reckoning from the time 

 when growth has certainly started, it is found that the mean life period (T) 

 of the tumour cells in the animals of the different series vary in the 

 following manner : — 



Control cells (mean of 6 animals) ... ... . . T = 34 days. 



\ hour irradiated cells (mean of 6 animals) ... T = 3 - 9 „ 



i „ „ » 3 „ ... T = 8-3 „ 



1 „ „ (one animal) ... ... T = 5 - 6 „ 



Attempted Re-activation of Irradiated Tissue. 



The changes produced in the tumour tissue by the irradiation may be 

 internal or external to the cells, or the cell boundaries may be affected. 



If a tumour be minced by a Haaland mincer, as has been done in this work 

 and the emulsion be vigorously centrifugalised, about 1 c.c. of fluid may 

 generally be pipetted off from 20 grm. of tissue. If the failure of the 

 tumour to grow after irradiation be due to changes occurring external to the 

 cells, such changes might possibly be counteracted by taking tissue that had 

 been irradiated sufficiently long to prevent its growth and adding to it fluid 

 obtained from non-irradiated tumour tissue in the manner indicated. 



This re-activation test has been put into operation three times, the extent 

 of irradiation having been 1 hour 4 mins., 2 hours 35 mins., and 5 hours 



