212 Dr. Russell. The Manifestation of Active [Mar. 15, 



Expt. T/27 C. Success of primary inoculation = 83 per cent. 



Re-inoculation of 

 positives. 



Ee-inoculation of 

 immunised positives. 



Re-inoculation of 

 immunised controls. 



Control to 

 re-inoculation. 



10 in 13 

 [ 77 per cent. 



3 in 12 

 25 per cent. 



1 in 15 

 7 per cent. 



6 in 8 

 75 per cent. 



Three further experiments on these lines were performed with the same 

 strain ; the intervals elapsing between the several inoculations were main- 

 tained, but the tissue employed to induce the resistance was varied. The 

 behaviour of carcinoma 91 was also tested on two separate occasions. 



On summing up the total figures obtained in the six experiments the 

 change induced can be seen, as in the following totals : — 



Re- inoculation of 



Re-inoculation of 

 immunised positives. 



Inoculation of 

 immunised controls. 



Control to 

 re-inoculation. 



41 in 65 

 63 per cent. 



19 in 70 

 27 per cent. 



22 in 95 

 23 per cent. 



51 in 69 

 73 per cent. 



Whereas 63 per cent, of mice bearing tumours of these two strains have 

 been shown to be receptive to a second inoculation, this figure is reduced 

 to 27 per cent, when the second inoculation is preceded some 14 to 16 days 

 by the injection of an immunising dose of tissue. The figures are too large 

 to allow the simple interpretation of the results as the expression of an 

 involuntary selection. The percentages given in Columns 2 and 3, which 

 deal with the " immune reaction " in tumour-bearing mice and in normal 

 mice respectively, show that, in general, mice with tumours can be rendered 

 resistant with almost the same facility as normal mice. 



When carrying out the experiments upon the immunisation of mice 

 bearing tumours, described in full in the preceding pages, some cases were 

 noted where the tumour, which had already started growth before the 

 immunisation was carried out, was retarded greatly in its growth, or even 

 totally inhibited. If this result could be regularly obtained, the cure of 

 transplanted tumours which did not disappear spontaneously would be 

 accomplished. Strains of tumours which grow progressively were tested 

 by subjecting the mice bearing them to the inoculation of embryonic tissue 

 or of tumour tissue, which disappeared spontaneously. The effect of single 

 inoculations of varying amounts of immunising tissue was tested, and also 

 the repetition of the immunising dose at various intervals of 7, 10, and 



