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ROYAL SOCIETY OF CANADA 



13 days the cultures were put at 18° to 22° C. and in 18 hours 1^ and 

 5^ became Prussian blue throughout and later all the lactose agar tubes 

 showed pigment. 



Conclusions. — On agar with lactose, growth and pigmentation were 

 retarded by low temperatures, but not prevented even by temperatures 

 near freezing. At low temperatures lactose 20^ or more restrained 

 growth and prevented pigmentation. 



Growth at High Temperature. — The organism did not grow in 

 milk at 38.2° C. nor in synthetic media at 39° C. 



Thermal Death Point. — The medium used was peptone 1^ in tap 

 water and each test tube of thin walled glass contained 10 c. c. of the 

 clear sterile medium. 



Tubes were selected which would float upright in the water bath, 

 the water being as high as the bottom of the cotton plugs. The bath 

 contained 8 litres of water and a thermometer with its stem passing 

 through a cork floated upright in the water and reached half way to 

 the bottom. The bath was heated by a gas flame below and the tubes 

 were left in the water long enough to acquire the correct temperature 

 before they were inoculated. 



The tubes were inoculated from a culture in Dunham's solution 

 + 10^ dextrin which had been incubated 3 days at 25° to 27° C. It 

 had become viscid and pigmented. 



The tubes were inoculated without raising them from the bath, 

 each tube receiving three 2 m.m. loopfuls of the culture. Two tubes 

 were exposed at each temperature and for each period. During the 

 exposure the temperature did not rise above those recorded nor fall more 

 than .5° C. At the end of the exposure the tubes were plunged in cold 

 running water and when they were cool they were incubated at 25° 

 to 27° C. 



'Control tubes were inoculated, but not heated and these, together 

 with some of the heated tubes, became turbid in 24 hours, others after a 

 few days. In 24 hours some tubes were clear and others turbid and 

 viscid with a ropy white sediment and a greenish pigment. 



Exposure 10 Minutes. 



