PRACTICAL DISINFECTION 565 



two hours at 131° F. Some investigators have failed to state 

 the temperature under which their disinfecting experiments 

 were made. 



5. In many of the results the inhibitory action of the 

 agent in question has been mistaken for its germicidal action. 

 After the bacteria have been subjected to the influence of a 

 disinfectant for a given time, though not killed, their vege- 

 tating aud pathogenic capabilities may be modified but still 

 able, under favorable conditions, to return to their former 

 vigor. 



The rules and recommendations of the various cattle com- 

 missions and those having authority in methods for prevention 

 of infectious diseases of animals do not very clearly define the 

 procedures best adapted to the various places and conditions 

 requiring disinfection. The many chemicals possessed of 

 germicidal powers and the numerons commercial disinfectants, 

 recommended largely from the results of certain definite tests, 

 which in point of fact may be of no value in determining their 

 efficiency for the conditions in question, render further inquiry 

 into the best methods for disinfecting after animal diseases a 

 matter of much scientific interest and great practical value. 



§ 453. Conditions to be taken into account in practical 

 disinfection. In the effort to destroy the microorganisms in 

 such places as yards, stables, cattle cars and the like, it is neces- 

 sary to consider before applying a disinfectant the following 

 conditions : 



1. The resistance of the particular organism to be de- 

 stroyed. 



2. The medium or material in which it exists. 



3. The nature of the place containing the organism to be 

 destroyed. 



4. The chemical action of the material surrounding the 

 microorganisms on the disinfectant itself. 



If the disinfection is for anthrax or Texas fever (cattle 

 tick) a more powerful substance or solution must be employed 

 than would be required in disinfecting for the bacteria of 



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