316 GERMICIDAL ACTIVITY OF EUCALYPTUS OILS, ii., 



Stronger dilutions were tested at shorter intervals, but as tlie 

 tube method, on account of the apparent necessity for keeping 

 the oil emulsified, was considered impracticable, wide-mouthed 

 ounce-bottles containing lOc.c. of emulsion were cooled to 20°, 

 and each was treated with five drops of a 20-hour broth culture 

 and shaken repeatedly during the period of exposure. The 

 results were very irregular, much more so than with more dilute 

 emulsions, and the reason for this was not at once elucidated. 

 One test showed that a greater amount of shaking lessened the 

 lethal exposures, but when the shaking was regulated, the results 

 were no more uniform. Differences in the reaction of the broth, 

 which is claimed by J. H. Wright* to cause discrepancies in the 

 results obtained in testing disinfectants, did not account for 

 those obtained by me, for tests were made with dilutions of 

 cineol, 1 : 100, which after exposures of 2, 4, 6, 8, and 10 

 minutes, were seeded into tubes of broth varying in reaction 

 from +3° through 6°, 8, 10° to -f- 12", and all showed no growth 

 in 6 minutes. 



The phenol tests were always fairly constant; in fact the 

 broth cultures used for infecting the tests were controlled by 

 the bacteria being destroyed in 6 minutes by a 1 : 80 solution of 

 phenol at '20°. If a shorter or a longer time was taken to 

 destroy the bacteria, the experiment was rejected, and the 

 cultures examined to obtain a mixture of races capable of being 

 destroyed under the conditions in six minutes. 



In considering the uniformity of the phenol tests and the 

 comparative regularity of the tests with the weaker dilutions of 

 cineol, it would appear that an irregularity of result is to be 

 expected in dealing with strong emulsions which separate so 

 readily as do mixtures of cineol and distilled water. I have, 

 therefore, recorded the results of the tests, irregular as they are 

 and have calculated the general average which enabled a curve 

 of probable efficiency to be made. 



Through Abs. of Back. 1918, 78. 



