20 S 



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



Murray's studies* upon the heredity of cancer have shown that it is 

 possible to breed out families of " mice whose members will show an 

 extremely high incidence of cancer, although they are not more suitable 

 for the implantation of a transplantable tumour than mice not specially 

 bred.f 



Cuenot and MercierJ have made the attempt to breed out from one and 

 the same strain of mice families suitable and unsuitable for the implantation 

 of cancer. They claim to have isolated two families, in one of which a tumour 

 strain will take in 86 per cent., whereas in the other it will only take in 20 per 

 cent. Should these findings be confirmed, and it seems desirable that they 

 should be repeated and tested with a variety of tumours, they would help greatly 

 to explain the character of growth exhibited by such strains as 199. It might 

 be possible to isolate families of mice in which this strain produced no 

 resistance, and the inoculation would lead to the development of progressively 

 growing tumours in all cases. 



Variations in the power of tumour parenchymata to induce resistance may 

 be made in part responsible for the adaptations which tumours undergo 

 more especially during their earliest transference to new hosts. When a 

 spontaneous growth is transplanted, there is usually a rapid rise in the 

 percentage of success attached to the first three or four passages. Might it 

 not be possible that the rapid rise in transplantability is due to a greater or 

 smaller loss of the power of the tumour parenchyma to induce resistance ? 

 This possibility requires consideration because careful microscopic examination 

 of grafts during the first 10 days shows normal growth in nearly every case, 

 even although the tumour strain only gives in control series an eventual 

 percentage of success of about 40. The natural resistance of animals to 

 tumour inoculation is a phrase which has been much employed, but it might 

 perhaps be more correct to speak of animals which readily develop an active 

 resistance. 



The next question to be discussed is, how do the results obtained by 

 re-inoculation after the first tumour is removed compare with those obtained 

 when this growth is not interfered with ? It may be stated at once that the 

 results obtained under the two conditions are exactly identical, and the 

 removing or leaving behind of the tumour first inoculated neither favours nor 

 hinders specifically the development of the second one. That a mouse 

 bearing an implanted growth can be successfully re-inoculated was recorded 



* Murray, J. A., "Cancerous Ancestry and the Incidence of Cancer in Mice," 'Eoy. 

 Soc. Proc.,' 1911, B, vol. 84, p. 42. 



+ Haaland, M., " Spontaneous Cancer in Mice," 1 Eoy. Soc. Proc.,' B, vol. 83, p. 532. 



% Cuenot, L., et Mercier, L., "L'heredite de la sensibilite a la greffe cancereuse," 

 ' Comptes Rend, de FAcad. des Sciences,' 1910, vol. 150, p. 1443. 



