176 Dr. Bashford, Mr. Murray, and Dr. Cramer. [Dec. 10, 



uniform in this series. Out of 95 mice inoculated, 59 developed tumours on 

 both sides, five on the right side only, and 11 on the left side only. The two 

 strains, propagated in the right and left axilla respectively, fluctuated 

 practically independently of one another, at one time a higher percentage was 

 obtained in the right axilla, at another time in the left. It is to be noted, 

 however, that whenever the strain with the lower percentage for the time 

 being was able to establish itself on its side, the tumour giving a higher 

 percentage always succeeded in establishing itself on the opposite side of that 

 individual mouse, so that a tumour of the strain with lower percentage never 

 occurred singly, each had its fellow on the opposite side in the more numerous 

 tumours of the high percentage strain. Hence the differences in percentage of 

 success between the two strains are considered to be due to fluctuations in the 

 powers of proliferation of the cells of each, and to be independent of the 

 susceptibility or resistance of the mice in which they are, or have been, 

 growing. If the resistance of the mice in the right or left axilla be assumed 

 to be similar, then this resistance really serves merely as a measure of the 

 varying qualities of the tumour cells. It plays the part of a sieve, as it were, 

 which keeps back the cells with less powers of assimilation and growth, and 

 permits those others to pass which can survive the hindrance to their 

 continued existence and multiplication. 



(3) Mice in which a Growing Carcinoma has been Spontaneously 

 Absorbed may be Completely Protected against Subsequent 

 Inoculation of the same Growth and to a lesser extent 

 against other and different growths. 



Animals in which tumours have developed and then have been absorbed 

 are highly refractory to further inoculation. This protection may be 

 absolute. This fact is sufficiently evidenced by the following experiments. 

 The animals were re-inoculated in another part of the body after complete 

 disappearance of the first tumour. The control animals were inoculated in 

 the same place as the second experiment of the spontaneously-recovered 

 mice. 



Protocol to Illustrate Absolute Protection after Spontaneous Absorption. 



A. Experiment 61, ii M (1). Tumour taken from a mouse of transplantation 60, 

 Series V, was transplanted into the right axilla of 20 normal mice. Eight tumours 

 developed in the 12 animals surviving after 10 days (64 per cent.). 



(2) The same tumour was also inoculated at the same time into 36 mice which had been 

 previously inoculated successfully in the right axilla, but in whom the tumours evident 

 %fter 10 days ultimately disappeared. Two small tumours developed in the 33 animals 

 surviving after 10 days (6 per cent.). 



