372 DISINFECTION 



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 and 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 numerous 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 practical value. 



§ 301. Conditions to be taken into account in practi- 

 cal disinfection. In the effort to destroy the microorganisms 

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

 necessary to consider before applying a disinfectant (i) the 

 resistance of the particular organism to be destroyed, (2) the 

 medium in which it exists, (3) the nature of the place con- 

 taining the organisms to be destroyed and (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 septicaemia hemorrhagica. If the infecting organ- 

 isms are mixed with fecal matter, dirt or fodder, the problem 

 is a different one than where they rest on a comparatively clear 

 surface. It matters again whether the infecting organisms are 

 in the soil (on surface), on a stable floor that is tight and hard 

 or on one containing cracks of various sizes and made up ot 

 board, more or less shattered or decayed, thus furnishing deep 

 recesses for the hiding away as it were of the specific organisms. 



