1913.] Rays upon the Cells of Jensen's Rat Sarcoma. 487 



40 mins., to a concentration of §-'57, O40, and 0"37 millicuries per cubic 

 centimetre respectively. The technique followed was practically the same 

 in each case. 



To some of the irradiated tumour emulsion an equal volume of fluid 

 obtained from non-irradiated tumour tissue was added and after allowing the 

 fluid to permeate the irradiated tissue for about 1 hour, 01 c.c. of the 

 emulsion was inoculated into a number of normal rats (i.e. 6 or 8). 



To another portion of the irradiated tumour emulsion an equal volume of 

 normal saline was added, and 01 c.c. of the mixture inoculated into (6 or 8) 

 other rats to serve as controls. At the same time O'l c.c. of fluid only 

 was injected into a number of rats. No reaction was detected when fluid 

 only was injected. In no one of the cases was the attempt at re-activation 

 successful to the extent of the ultimate production of a growing tumour; 

 indicating that the changes occurring in the tumour tissue as a result of 

 irradiation cannot be counteracted by the action of non-irradiated tumour 

 fluid, and that the irradiation probably causes some change in the cells 

 themselves. 



Charts of the animals show that 17 clays subsequent to the inoculation of 

 the irradiated emulsion treated with fluid, 16 animals out of 22 showed 

 palpable nodules, compared with 4 out of 21 of the control animals. This 

 result suggests that normal tumour fluid has some action upon the 

 irradiated cells, which delays their absorption by the animal although 

 ineffective in re-activating them. 



Histological Examination. 



To study the histological changes which occur in the irradiated material 

 after inoculation, three series of rats (36 in all) were inoculated on one 

 side with - l c.c. tumour emulsion, and on the other side with - l c.c. of 

 the same emulsion which had been exposed to a concentration of about 

 - 45 millicurie per cubic centimetre for periods of 20 minutes (a), 

 80 minutes (b), and 24 hours (c). These times of exposure ensure that 

 the grafts will (a) be slightly delayed in growth, (5) just fail to develop 

 into tumours, and (c) show no signs of proliferation, respectively. An 

 animal from each series was killed each day for the first week, and then 

 at intervals until the 22nd day after inoculation, the control and irradiated 

 tumours were excised and sections prepared. 



Microscopical examinations of the emulsions, after irradiation and before 

 their inoculation into the rats, failed to establish any differences between 

 them and the non-irradiated portions. 



