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



be exposed to X-rays before inoculation, measurable tumours result, and the 

 study of grafts shows that considerable growth of sarcoma occurs ; at the 

 same time, profound changes take place in the spleen ; lymphocytes, and, to a 

 less extent, plasma cells, are completely destroyed. 



Our observations as to the effects of X-rays upon the immune condition 

 are confirmatory of the experiments on similar lines initiated by Murphy and 

 Morton (5), who showed that mice immunised with defribrinated blood could 

 be rendered susceptible to mouse carcinoma by a suitable exposure to X-rays. 



Murphy (6) has also shown that the chick embryo, up to the 18th day, 

 will support the growth of rat sarcoma, but that if, during this period, 

 adult chicken spleen or bone marrow be inoculated, then the established rau 

 sarcoma will be destroyed. It was found that this destruction was associated 

 with an accumulation of lymphocytes in the connective tissue around the 

 sarcoma. 



Other evidence that the lymphocytes, and less certainly plasma cells, are 

 an important factor in the condition of immunity is, however, forthcoming. 

 The evidence of grafts study is very strong, and it does not appear necessary 

 to repeat this again ; the reader is here referred to Part II. (1) The Role of 

 the Lymphocyte, and also to the observations of da Fano {loc. cit.). 



Eeference may be made again to the fact that sarcoma cells are able to 

 survive in an immune rat for three days, and that this is the period at which 

 the local accumulation of lymphocytes around the inoculated material reaches 

 its maximum. Finally, it may be pointed out that, just as the destruction of 

 sarcoma cells, when introduced into an immune rat, is always associated with 

 a local accumulation of lymphocytes, so when the growth of an established 

 tumour begins to be controlled, there is likewise a great accumulation of 

 lymphocytes in the immediate neighbourhood of the tumour. 



It may therefore be concluded that lymphocytes play an important part 

 in the process by means of which an animal is able to destroy sarcoma cells, 

 and that their local presence is necessary for this destruction, and that in 

 their absence locally the sarcoma cells will proliferate. 



We are, as yet, entirely ignorant of the mechanism by means of which the 

 lymphocyte is brought to the sarcoma oelL The facts indicate that the 

 lymphocyte does not merely act as a scavenger of sarcoma cells, killed, for 

 instance, by some toxin ; for if this were the case, it must be assumed that 

 such actions as splenectomy and X-ray exposure destroy the toxin as well as 

 the lymphocyte, unless the toxin is secreted by the lymphocyte, which is a 

 possibility to be taken into account. The exact time . relations between 

 lymphocyte accumulation and sarcoma degeneration have not, as yet, been 

 thoroughly worked out ; but from the study of grafts, the degeneration is 



