164 



The Natural and Induced Resistance of Mice to the Growth of 



Cancer. 

 By E. F. Bashford, M.D., J. A. Murray, M.B., and W. Cramer, Ph.D. 



(Communicated by Dr. J. Eose Bradford, F.R.S. Eeceived December 10, 1906, — 



Read January 17, 1907.) 



In the present paper we propose to give an account of experiments 

 conducted during the past three years on the means whereby mice may be 

 completely protected against the inoculation of transplantable careinomata, 

 which grow readily in normal mice. At the same time we shall show that 

 these experiments throw fresh light on the nature of cancer. The Executive 

 Committee and the Pathological Sub-Committee of the Imperial Cancer 

 Research Fund have been informed of the progress of these investigations, 

 and. some provisional results have also been laid before the General Com- 

 mittee at the Annual Meetings. The experiments are being continued, 

 but some of the results which have accumulated, make it advisable to give 

 an account of the stage at which they have now arrived. They are based 

 mainly on a study of 23 transplantable carcinomata of the mamma of the 

 mouse, and of other malignant new growths which could not be propagated 

 artificially. 



In these experiments we have used, for the most part, the growth of 

 Jensen's tumour in normal animals to bring out the changes induced in 

 protected animals and the refractoriness of insusceptible animals ; but we 

 shall also employ another tumour (XXVII) of different histology, which 

 grows equally well under artificial propagation. We have employed Jensen's 

 tumour as a standard for the following reasons : — (1) It was the only tumour 

 used to control some of our earlier observations ; (2) With proper precautions 

 it gives regularly 85 to 100 per cent, of successful inoculations in a large 

 number of animals ; (3) Within ten days the inoculation of - 01 to 

 0*02 gramme of tumour tissue gives large easily recognisable tumours, often 

 1-5 grammes in weight ; (4) We have fully demonstrated that it may produce 

 large metastases, that it may extend by the blood or lymphatic streams, and 

 behave under experimental conditions typically as a malignant new growth ; 

 (5) Its rate of growth is not exceeded by any mouse tumour now being 

 propagated ; (6) It is in the hands of most investigators throughout the 

 world, who will be able to repeat our observations. It therefore fulfils 

 better than any other tumour the requirements of such a standard. 



