MAXIMUM TEMPERATUKE. 33 



MAXIMUM TKMl'KUATUUK. 



In determining the niaxinunn toniperaturo at which the calla-rot 

 organism will grow several media were used, viz, agar, gelatin, beef 

 })roth, and Uschinsky's solution. These media were iuoculat(>d with a 

 24-hour-old culture of the calla-rot organism in beef 1)roth, and several 

 tubes of each medium were placed in an incul)ator which registered 

 40° C. At the expiration of forty-eight hours the temperature still 

 •remained at 40° C, and there was no visible growth in any of the 

 media. Growth was apparent in all the control tubes at the end of 

 twenty-four hours after inoculation. On the third day after the tubes 

 were placed in the oven the temperature fell to 38° C, and at the 

 expiration of twenty-four hours thereafter there was a visible cloud- 

 ing of the beef broth and of the Uschinsky solution, ])ut no groAvth 

 appeared on the other media. When the incubator had again ])ecome 

 steady at 40° C, fresh cultures were introduced, including, in addition 

 to the above mentioned media, milk, litmus milk, and poured-agar 

 plates. At the end of forty-eight hours there was a slight clouding 

 of the beef broth and of the Uschinskv solution, l)ut no growth was 

 yet apparent in the other media. Twenty-four hours later the clouding 

 in the beef broth and in Uschinsky's solution had increased and minute 

 colonies began to appear in the poured plates, slight growth l)eing 

 apparent also on slant agar and stab gelatin cultures. At the end of 

 another twenty-four hours the milk was slightly curdled and the 

 litmus milk was beginning to redden. The temperature remained 

 constantly at 40° C, and growth advanced slowly in all cases for 

 several days. The colonies in the poured plates increased in size until 

 they were from 2 to 3 mm. in diameter. It should be noted that all 

 the colonies produced on the agar plates at this high temperature were 

 round, none of them showing any tendency to radiate as they did 

 ' under temperatures from 20° to 30° C. While 40° C. retards the 

 growth of the organism it does not prevent it. The incubator Avas 

 next ]-egulated at 41° C. and fresh cultures of the organism on the 

 various media were placed in it. After forty-eight hours there \vas a 

 slight growth in the Uschinsky solution and on the slant agar, but it 

 was very slight as compared with the controls. No growth appeared 

 in the other media. At the end of another forty-eight hours, growth 

 in the agar and in the Uschinsky solution was not perceptibly advanced 

 and no growth appeared in any of the other media. Upon removing 

 all these cultures to conditions of normal temperature at the end of 

 the fourth day, growth advanced rapidly in those cases where it had 

 started and appeared in all the other media used w^ithin twenty-four 

 hours after removal. When fresh cultures were kept constantly at 

 42° C. no growth appeared, but exposure to this temperature for 

 twenty -four hours did not destroy the life of the organism, as evidenced 



27501— No. 60—04 3 



