1912.] Resistance to the Groivth of Implanted Cancer. 209 



from this laboratory as early as 1904,* and more extended researches led to 

 1 the formulation of the dictum that the better the first tumour grows the 

 more favourable are the chances of the second inoculation being successful.f 

 In a paper by Bashford, Murray, Haaland, and BowenJ the conclusion was 

 drawn that negative results on re-inoculation of an animal already bearing a 

 tumour were due to the development of concomitant immunity, and the view 

 was rejected that the negative result was attributable to an exhaustion of 

 specific food-substances (athreptic immunity) by the first tumour. The latter 

 view is still upheld by Apolant,§ but in one of his later papers the accom- 

 panying charts show that after removal of the first tumour the majority of 

 the. animals, rats and mice, are resistant to re-inoculation, which is scarcely in 

 harmony with the hypothesis he entertains. 



The conclusion is inevitable that tumour parenchymata vary widely in the 

 •extent to which they alter the suitability of an animal for growth of a 

 subsequently implanted tumour, and that this alteration of the suitability of 

 the animal is due to the development of an active resistance or immunity. 



A clear recognition of differences in the behaviour of transplanted tumours, 

 induction of resistance in a high percentage of cases on the one hand, contrasted 

 with practically total absence on the other, led to a study of the influence 

 which a strain of the former type might have upon the growth of a tumour 

 of the latter type, where both tumours were inoculated at the same time. 

 Simultaneous inoculation of two tumours in opposite axilla; has already been 

 carried out. Bashford, Murray, and Cramer|| inoculated two separate strains 

 of the same tumour in the right and left axilla respectively for five successive 

 passages, and found that each tumour strain varied in its growth quite 

 independently. BridrelT also performed the double inoculation of two separate 

 strains, and found that each grew as if it alone had been inoculated. 



When, however, double inoculation is carried out with tumours of different 

 types of growth, the two tumours do not grow independently of each other. 



* Bashford, E. F., and Murray, J. A., " The Transmissibility of Malignant New Growths 

 from one Animal to Another," 'First Scientific Report of the Imperial Cancer Research 

 Fund,' London, 1904, p. 11. 



t Loc. cit., p. 205. 



I Bashford, E. F., Murray, J. A., Haaland, M., and Bowen, W. H., "General Results of 

 Propagation of Malignant New Growths," ' Third Scientific Report of the Imperial Cancer 

 Research Fund,' London, 1908, p. 262. 



§ Apolant, H., "Ueberdie Immunitat bei Doppelimpfungen von Tumoren," 'Zeitschr. 

 f. Immunitatsforsch.,' 1911, vol: 10, p. 103. 



|| Bashford, E. F., Murray, J. A., Cramer, W., " The Natural and Induced Resistance 

 of Mice to the Growth of Cancer," ' Roy. Soc. Proc.,' 1907, B, vol. 79, p. 164. 



IT Bridre, J., " Recherches sur le Cancer Experimental des Souris," 'Ann. de PInstitut 

 Pasteur,' 1907, vol. 21, p. 760. 



