DISINFECTION AND DISINFECTANTS 249 



found that at lower temperatures the activity of the 

 emulsion is raised more rapidly than that of the solution, 

 but at the higher temperatures used the activity of the 

 emulsion is no longer increased in proportion to the 

 increase in the activity of the carbolic acid. 



Two disinfectants used together may be more efficient 

 than either separately. Conversely, mixture of others 

 ma}* diminish or neutralise the efficiency of the com- 

 ponents. One species of bacteria may be many times 

 more sensitive to one disinfectant than to another, when 

 both substances exert an equal effect on a second species. 

 In a less degree, varying degrees of susceptibility to the 

 same disinfectant are exhibited by different strains of 

 the same organism. Repeated subculture on favourable 

 media will often increase resistance to chemical dis- 

 infection. By culture in media containing non-toxic 

 proportions of a disinfectant, an enhanced degree of 

 resistance to this disinfectant may be acquired temporarily. 



Chick and Martin find that finely particulate matter 

 affects the value of emulsified disinfectants containing 

 the higher phenols more than it does phenol, and the loss 

 is the greater the finer the emulsion. The removal of 

 an emulsion of higher phenols by organisms is a process 

 of adsorption at first, in which the organisms are sur- 

 rounded by concentrated disinfectant, and so dis- 

 infectants of this class possess a higher efficiency. King- 

 zett and Woodcock, however, found that the fall in 

 germicidal value generally shown when disinfectants 

 are examined by the Lister Institute method was not due 

 to the mechanical action of the solid matter (fseces). They 

 showed that when kieselguhr, powdered pumice, and 

 precipitated chalk were introduced into the water used 

 to dilute the disinfectant (Sanitas Bactox), there was no 

 depreciation in its coefficiency. 



Little is known of the destruction of the filterable 

 viruses by chemical agents. Saponine does not affect 

 bacteria, but Cockayne (Medical Press, February 12, 1913) 

 says it will kill filterable viruses, with the exception 

 of those of trachoma and Cyanolophia gallinarum. These 

 two also resist the action of taurocholate of soda, which 

 destroys the others. 



Points of Efficient Disinfectants. 1. Capability of 

 killing bacteria. A disinfectant capable of efficient action 



