1906.] Resistance of Mice to the Growth of Cancer. 167 



tumours, and Jensen's and our own experience, we then expressed scepticism 

 of the curative results claimed hy Clowes. In his later papers these results 

 are quoted, but a repetition of the positive results has not been recorded. 

 Evidence is adduced to show that the animals which have recovered 

 spontaneously cannot be successfully inoculated. This is regarded as an 

 action of anti-bodies. The presence of anti-bodies is further supported by 

 experiments in which tumour material had been exposed, in the test-tube, to 

 the action of the serum of spontaneously cured mice. On inoculation, such 

 material gave 12 per cent, of success, while material similarly treated with 

 normal mouse serum gave 31 per cent. These three sets of observations are 

 progressively evidence of a more limited action of the reputed immune sera. 

 The age of the animals used is not stated. In March, 1906, Ehrlich* 

 remarks with reference to these experiments : " So berichtet Clowes, dass 

 Mause, bei denen Tumoren spontan zur Eesorption gelangen, in ihrem Serum 

 carcinomfeindliche Stoffe enthalten. Allerdings lassen sich gegen die 

 Deutung dieser Versuche mancherlei Einwendungen machen." Other papers, 

 in which these and other observations are used as evidence of the infective 

 nature of cancer, have also been published by Clowes, Gay lord, and Baeslack, 

 from the Buffalo Cancer Laboratory, U.S.A.f 



MichaelisJ obtained success in the same proportion as in normal animals, 

 on inoculating mice previously treated with tumour material killed by 

 chloroform and other chemical agents. 



Ehrlich§ found that from 60 to 90 per cent, of mice inoculated unsuccess- 

 fully with spontaneous (especially hemorrhagic) tumours were refractory 

 on subsequent inoculation with a tumour giving 75 to 100 per cent, of success 

 in normal animals. Further, animals unsuccessfully inoculated with a 

 tumour giving nearly maximal percentage of success in normal mice, were 

 highly refractory to subsequent inoculation. This resistance was manifest 

 whether the second inoculations were made with the same or other tumours 

 (pan-immunity). Animals already successfully inoculated with a quickly 

 growing tumour could not again be inoculated with a rapidly growing tumour 



* " Experimentelle Carcinomstudien an Mausen," 'Arbeiten a. d. Kgl. Inst. f. exp. 

 Therapie,' 1906. 



t " On Spontaneous Cure of Cancer," ' Surgery, Gynaecology, and Obstetrics,' June, 

 1906; "Incubation of Mouse Tumours," ' Journ. of Exp. Medicine,' August, 1906; 

 " A Study of the Influence Exerted by a Variety of Physical and Chemical Forces on the 

 Virulence of Cancer in Mice," 'Brit. Med. Journ.,' December 1, 1906 ; "Evidences that 

 Infected Cages are the Source of Spontaneous Cancer developing among Small Caged 

 Animals," ibid. 



% ' Zeitschr. f. Krebsforschung,' vol. 4, 1906. 



§ "Experimentelle Carcinomstudien an Miiusen," 'Zeitschr. f. arzl. Fortbildung,' 

 1906, and loc. cit. 



VOL. LXXIX. — B. O 



