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



animals the accumulation of lymphocytes is delayed for as long as two weeks. 

 (A smaller dose of X-rays resulted in less delay.) 



Tlie accumulation of lymphocytes which occurs around the sarcoma cells, 

 which by then have grown to a measurable tumour, is precisely similar to 

 what is to be seen when tumours are either disappearing or oscillating. 



(2) The Behaviour of the Sarcoma Cells. 



Before attempting to correlate these facts, it is necessary to consider what 

 has been seen to occur as regards the behaviour of the sarcoma cells under 

 these same experimental conditions. In order that these facts may be 

 displayed side by side. Table V has been prepared; the conditions in 

 disappeax'ing, oscillating, and progressing tumours have been subjoined. 

 Detailed descriptions of the behaviour of the sarcoma cells have already been 

 given, and do not require to be again referred to in the text. 



On referring to Table V, it can be seen that, in susceptible animals, 

 lymphocytic accumulation only occurs when injured sarcoma cells are 

 inoculated ; and that where uninjured or dead cells are used, very slight 

 lymphocytic accumulation is found. Further, it can be seen that when great 

 accumulation occurs the animal is likely to be subsequently immune. 



In immune animals a delay in the accumulation of lymphocytes is seen to 

 be associated with a temporary growth of the sarcoma ; but that, later, when 

 accumulation of the lymphocytes takes place, the sarcoma cells die out, and 

 the animals remain unsusceptible. 



A similar correlation has been seen to hold in the case of tumours. 

 Animals bearing progressive tumours are usually susceptible, they do not 

 present accumulation of lymphocytes in the surrounding connective tissue ; 

 the sarcoma cells are in active division. On the other hand, animals bearing 

 disappearing or oscillating tumours are almost invariably immune, they 

 present great accumulation of lymphocytes ; the sarcoma cells are either 

 degenerated or not in, active division. 



(3) The Reaction Tissue of the Host. 



Apart from the differences already noted, the local reaction of the tissues 

 of the host appear to be the same in susceptible and immune animals. An 

 inflammatory oedema, lasting for 24 hours, is followed by the laying down of 

 a vascular connective tissue. It is important to note that the formation of 

 blood-vessels in the tissues occurs at the same time, and to the same extent, 

 in immune as in susceptible animals ; and that the failure of growth in 

 immune animals cannot therefore be accounted for by the failure of a 

 sufficient vascular supply. 



