POSTIRRADIATION TREATMENT OF MiCE AND RaTS 145 



In control tests carried out in parallel with the experiments 

 it was shown that CBA mice, previously inoculated with 

 tumour to give full transplantation immunity, on re-injection 

 with the test-dose of tumour returned weights for the im- 

 plants which varied from individual to individual and from 

 batch to batch within the range of 2 to 42 mg. On the other 

 hand normal, non-immunized CBA mice, while also varying 

 between individuals and between batches, had tumours 

 weighing 48-877 mg. Within batches there was in each case 

 a clear-cut difference, usually one to two orders of magni- 

 tude, between individuals of the positive control group and 

 individuals of the negative control group. The weights of the 

 tumours derived from the test-animals were compared with 

 these controls. The tumour-weight in an experimental animal 

 was taken to be significantly different from weights of the 

 non-immune controls if it was less than the mean minus twice 

 the standard deviation. 



In addition to the tissues, spleen, lymph nodes and liver, 

 the tissue-fluids, blood and peritoneal exudate, were also 

 assayed for the antigen of strain A. Peritoneal exudates were 

 induced by prior injection of sterile paraffin and consisted of 

 lymphocytes and mononuclear cells. 



The results of the tests for A antigen in the tissues 

 and tissue-fluids of the irradiated CBA mice treated with 

 intravenous injections of strain- A spleen are shown in 

 Table I, overleaf. These figures show that the spleen and 

 lymph glands of these animals usually give significantly 

 positive results from the earliest time tested — 4 days. The 

 positive results persist until the latest time of test — 51 

 days. Peritoneal exudates also gave positive results through- 

 out the time of test, 16-51 days. On the other hand 

 liver and blood, tested only at 14 days, gave negative 

 results. 



Similar tests were conducted with tissues from unirradiated 

 CBA mice injected intravenously with suspensions of spleen 

 from strain-A mice. The results are given in Table II, over- 

 leaf. These results indicate that the injected A cells may 



