24 Mr. J. C. Mottram and Dr. S. Russ. Susceptibility and 



surrounding connective tissue. Subsequently the lymphocytes decrease in 

 numbers whilst the sarcoma cells multiply and form a tumour. 



Grafts of Boiled Sarcoma in Normal Animals. — At the end of 24 hours the 

 surrounding tissues are hardly at all oedematous, and subsequently there is 

 no reaction tissue comparable to that seen when living sarcoma cells are 

 inoculated ; there is no accumulation of lymphocytes, fibroblasts make their 

 appearance early and shut o(f the inoculated material from the tissues of the 

 host by scar tissue. 



' Grafts of Irradiated Sarcoma in Normal Animals. — Experiments by 

 Chambers and Kuss {loc. cit.) have shown that if sarcoma emulsion be exposed 

 to a concentration of 0"45 niillicurie per cubic centimetre for periods of {a) 

 20 minutes, (h) 80 minutes, and (c) 24 hours, on inoculation into normal rats, 

 there result (a) grafts which grow at a diminished rate, (h) grafts which just 

 fail to grow, and (c) grafts which present no sign of proliferation. 



In the 24-hour irradiated specimens only a few sarcoma cells are seen 

 outside the cleft, no mitosis occvirs, degenerative changes begin early and 

 the sarcoma cells soon die out ; a moderate amount of lymphocytic infiltra- 

 tion occurs at an early date. lu the 80 minutes irradiated grafts considerable 

 proliferation of the sarcoma cells takes place, but later, degenerative changes 

 supervene which are accompanied by an intense accumulation of lymphocytes; 

 the sarcoma cells eventually die out. 



The 20 minutes irradiated specimens present proliferation of sarcoma 

 cells ; on about the eleventh day some of these appear degenerated, and at 

 this time some lymphocytic infiltration occurs ; subsequently the degenerated 

 sarcoma cells and the lymphocytes disappear, whilst the remaining healthy 

 sarcoma cells continue to proliferate in a normal manner. 



5. The Microscopic Appearances of Disappearing and Oscillating Tumours. 



In the connective tissues surrounding these tumours a great accumulation 

 of lymphocytes is to be seen, which contrasts with the relative absence of 

 these cells in progressive tumours. 



Lymphocytes are also seen to be mixed with the marginal sarcoma cells, 

 which present decided degenerative changes. It is only towards the centre 

 of such tumours that healthy sarcoma cells are to be seen, in places where 

 there is no lymphocytic invasion. In the surrounding connective tissue, 

 accumulations of plasma cells occur around the blood-vessels, but only a few 

 of these cells are to be seen mixed with the sarcoma cells. The regression 

 of a tumour proceeds from without inwards, and is accompanied by a gradual 

 invasion of lymphocytes ; eventually the tumour is replaced by a fibrous 

 connective tissue, containing lymphocytes and collections of plasma cells. 



