REACTIVITY OF MALIGNANT NEOPLASMS 243 



tiimor-beariii" mice. The epidemic ^vas discovered by bacterio- 

 logical examinations shortly after its onset. The infected tumor- 

 bearing mice can be conveniently grouped according to the nor- 

 mal mortality rate, mortality rate considerably aboxe normal 

 expectancy, and the normal mortality rate following the disap- 

 pearance of the epidemic, as follows: 



Group 1 includes tumor passages made from Sept. 28 to Nov. 

 30, 1934, in 314 stock mice that '^vere free from spontaneous in- 

 fection. During the first tAvelve days there was a mortality rate 

 of 6.7 per cent. Twelve days after inoculation the 202 surviving 

 mice were examined. 



Group 2 includes passages made from Dec. 8, 1934 to March 8, 

 1935, in 610 mice infected with B. enteritidis. During the first 

 twelve days there was a mortality rate of 25.4 per cent. The size 

 and appearance of the tumors t^velve days after inoculation ^vere 

 recorded for 377 mice. 



Group 3 includes passages made from March 8 to April 3, 1935, 

 in 200 mice that were free from infection. Two per cent of 

 these mice died during the first t^velve days. The size and appear- 

 ance of the tumors t^velve days after inoculation ^vere recorded 

 for 133 mice. 



The incidence of "takes," tiny necrotic tumors, average-sized 

 growth and large tumors in the above groups is recorded in 

 Diagram 3. 



As may be seen from Diagram 3, spontaneous infection ^vith 

 B. enteritidis exerted a profotnid influence on the de\'elopment of 

 sarcoma 180, the number of "takes" being reduced by approxi- 

 mately 23 per cent. This is significant in \ iew of the fact that 

 under normal conditions the inoculations rarely failed to "take" 

 provided the precaution of selecting firm and healthy, approxi- 

 nrately twelve to fourteen day old tumor tissue 'was observed. 

 The ttmiors attained the a\'erage size in the usual percentage of 

 mice two \\'eeks after inoculation. Ho^\'e^er, the growth energy of 

 tumors in the infected mice ^vas apparently considerably reduced 

 as they did not sho^v the 3-)- and 4-^ tumors observed in ap- 

 proximately 50 per cent of the non-infected mice at that period. 

 One is also impressed by the high incidence of tiny necrotic 

 tumors. Histologic section oi a twelve day old tumor of this 

 type (Fig. 24) sho^ved a pronounced hemorrhage, necrosis of 

 ttmior cells, and thrombosis. \Vhene\er mice showino- necrotic 



