311 



THE GERMICIDAL ACTIVITY OP THE EUCALYPTI'S 



OILS. 



Part ii. The Action of the Oils in Aqueous Dilutions. 



By 1C Greig-Smith, I). Si.. Macleay Bacteriologist to the 



Society. 



(With seven Text-figures). 



In Part i. of this contribution. T dealt with the germicidal 

 activity of the Eucalyptus oils when dissolved in a neutral oil 

 such as olive oil, and it was shown that under such conditions the} 7 

 were poor disinfectants. The phenol-coefficients, against B. coli 

 communis at 20° for two hours, ranged from 04 with the oils of 

 E. linearis, E. cinerea, rect., and E. australianu, crude, 3rd hour, 

 down to 007 with cineol and the oil of E. polybractea. 



In this paper, an examination has been made of their germi- 

 cidal powers when in aqueous dilution. 



It is a difficult matter to determine the real, hygienic or 

 economic value of a disinfectant, for so much depends upon the 

 material in which the bacteria are contained. They may be sus- 

 pended in blood, pus, sputum, urine, sewage, water, trade waste, 

 etc., all of which have variable influences in absorbing or render- 

 ing inert the disinfectant. The proteids and fat are among the 

 most active destroyers of the disinfectants, and in considering 

 their virtues the nature of the bacterial menstruum or, as it is 

 called, their environment, has to be taken into account. The 

 coal tar products, for example, have their powers seriously reduced 

 by fat, in which they are more soluble than in water, while the 

 metallic disinfectants, such as mercuric chloride, are weakened 

 by proteids with which they form compounds. The oxidising 

 disinfectants are more or less used up in oxidising the organic 



