LABORATORY AND GREENHOUSE STUDIES. 125 



failed to cloud. Higher temperatures were not tried. Tlie thermal 

 death point is at least above 56° C. 



A repetition of this exj)eriment gave the following results: The six 

 coconut cultures and four strains of Bacillus coli exposed 10 minutes 

 to a temperature ranging from 59.2° to 59.6° C. failed to cloud in 48 

 hours at 37° C; the same series exposed for 10 minutes t^ a tempera- 

 ture ranging from 57.4° to 57.8° C. failed to cloud in 48 hours at 

 37° C; the same series exposed for 10 minutes to a temperature 

 ranging from 56.4° to 56.6° C. failed to cloud in 48 hours at 37° C. 

 with the exception of Bacillus coli (Ilitchings) . None of the coconut 

 cultures and only this one strain of the four Bacillus coli strains sur- 

 vived this experiment. It is reported in some textbook of bacteriology 

 that 59° C. is the thermal death point of Bacillus coli. However that 

 is, it is certain that none of the organisms used survived 57° C. in 

 this experiment. It was seen in the preceding experiment that aU 

 the coconut cultures exposed to a temperature of 54.85° to 55.15° C. 

 grew weU, and that after an exposure to a temperature from 56° to 

 56.10° C. three of the six tubes grew well. From these experiments 

 it would seem that the thermal death point of the coconut organisms 

 and of Bacillus coli is between 56° and 57° C. 



Miss McCulloch carried out the following additional tests in 

 November, 1910: Six coconut and the four Bacillus coli strains in 

 newly inoculated beef bouillon were subjected for 10 minutes to 

 temperatures of 56°, 57°, and 58° C, then incubated at 33° C. In 

 24 hours two of the Bacillus coli (B. A. I. and Hitchings) in the 56° C. 

 set were clouded; no growth in the 57° C. set; coconut No. 1 was 

 clouded in the 58° C. set. In 48 hours three of the Bacillus coli 

 (B. A. I., Hitchings, and VI-ll-V-09) were clouded in the 56° C. 

 set; no changes in the others. In 10 days no further change. 



Other experiments were" made, trying 55°, 56°, and 57° C. In 

 48 hours at 34° C. all of the 55° C. set, with the exception of coco- 

 nut Nos. 4 and 5, were clouded. Three strains of Bacillus coli 

 (Hitcliings, VI-ll-V-09, and XIV) and coconut No. 2 were clouded 

 in the 56° C. set. Coconut No. 1 and two strains of Bacillus coli 

 (Hitchings and B. A. I.) were clouded in the 57° C. set. In six 

 days coconut Nos. 4 and 5 were still clear in the 55° C. set. Coconut 

 Nos. 1, 2, and 3, and three Bacillus coli, in the 56° C. set clouded. 

 No further change in the 57° C. set. 



Desiccation. — Clean cover glasses were sterilized and drops of 

 the cultures were placed upon them, after which they were set away 

 in sterile petri dishes to dry out at room temperature. Cultures 

 dried two days clouded well in 24 hours. Those dried six days 

 clouded but little in the same time. Cultures dried 15 days were 

 still able to cloud the bouillon. 



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