294 



Dr. M. Haaland. The Contrast in the 



[Jan. 17, 



for more elaborate calculations, because of the only approximate value of all 

 such figures obtained by biological experiment. In all transferences of cancer 

 cells, small factors, such as health of the animals, intercurrent diseases — 

 factors which are incapable of exact measurement — play a very important 

 part in determining the results. 



The accompanying table illustrates the nature of results obtained, after the 

 inoculation of 0*10 c.c. of material, devitalised by grinding for 1|- hours at 

 the temperature of liquid air, when the mice are tested 15, 17, and 20 days 

 later, with varying doses, 0'02 to 0"05 of mammary carcinoma " 63." The 

 average weight of the tumours obtained in the treated mice when killed was 

 3'37, 3'2, and 4"75 grammes respectively, as against 2-03, 2'38, and 2'2 respec- 

 tively in the control mice. 



When the disintegration of the cells has been complete, not only does no 

 immunity follow upon the inoculation of 0*10 to 0"50 c.c. of the disintegrated 

 material, but in the majority of cases a distinct hypersensitiveness is induced 

 in the animals so treated. 



Varying the interval of time between the preliminary inoculation and the 

 testing inoculation shows that this hypersensitiveness is not a phase ante- 

 cedent to the establishment of immunity. There is as little evidence of 

 acquired resistance when the animals are tested at 30 days after the 

 preliminary treatment as there is at 10 and 20 days. 



The effect of inoculating varying doses of devitalised material has been 

 studied. When a scale of different doses ranging from 0"50 to 0"025 c.c. is 

 inoculated, the weight of the tumours obtained from the testing inoculation 

 shows that 0"10 c.c. gave a greater average weight of tumour than larger or 

 smaller doses. Although it would appear that the. intermediate dose of 

 O'lO c.c. offers optimum conditions for hypersensitiveness, even so large a dose 

 as 0'50 c.c. does not induce any increased resistance as compared witli the 

 normal animals of the same experiment. This is a relatively enormous dose, 

 and its inefficacy as an immunising agent shows that the absence of immunity 

 after the aVjsorption of (h'ad material is not inerel}' a question of too small 

 a dose. 



Having establislietl that tlie iumiunising power of tumours is abolished by 

 mechanically injuring the cells {i.e. with the minimal chemical alteration in 

 them), so that no growtli ensues, tlie (piestion next arises if tlie immunity 

 obtainetl by normal tissues runs the same course. Fig. 1 shows that this is 

 the case. In this experiment different balclies of nuce of about the same 

 age were treated, one set with an emulsion of frcisli Lota! mouse-embryo, 

 another with i\\v. same total mouse-embryo emulsion, ground in a mortar at 

 a tempcratiin! of 0° C. for 1^ hours; u third batch was treated witli fresh 



