100 Manual of Veterinary Microbiology. 



genie, may lead directly to the death of the latter; 

 we have already explained this action. 



2. Artificial disinfecting agents. — These are heat and 

 the antiseptics. 



Heat. — Heat is a powerful means of disinfection. 

 Although germs withstand extremely low tempera- 

 tures, they are very sensitive to increase of temper- 

 ature. Temperatures too low, as well as those which 

 are too high, are unfavorable to the proliferation of 

 pathogenic microbes ; but the latter are, in addition, 

 rapidly fatal. JSTevertheless, the spores are infinitely 

 more resistant than the adult germs; whilst these 

 last are killed in all cases between 50° and 100°, the 

 spores, on the contrary, require a temperature of 

 110° to 125°. However, we can with certaintv kill all 

 spores in a given infusion by bringing, on ditferent 

 occasions, and at intervals of one day, the said in- 

 fusion to a temperature fatal for the adult form, and 

 taking the precaution between the periods of heat- 

 ing to place the whole at a temperature favorable 

 for vegetation. The spores which the boiling has 

 not been able to attack become transformed into 

 adult bacteria which the heating of the next day will 

 destroy. 



Heat acts with more rapidity upon bacteria in the 

 moist condition than when dried, upon those of water 

 than upon those of the air. 



Whether we have to do with adult germs or spores, 

 with a dry medium or a moist, the duration of the 

 heating is of great importance and can be supple- 

 mentary to insufficiency of temperature. 



Antiseptics. — This name has been given to chemical 

 substances capable of destroying pathogenic germs or 



