98 Manual of Veterinary Microbiology. 



tion is known as disinfection. lN"ature comes power- 

 fully to their aid in this work of purification ; but it 

 often requires to be seconded by artificial means, the 

 application of which generally abridges the natural 

 duration of pandemic or panzootic diseases. We 

 have therefore to separate the causes which bring 

 about the destruction of pathogenic germs into 

 natural and artificial. 



It may be stated as a fundamental principle that 

 adult bacteria in their vegetative form are more rap- 

 idly destroyed, whatever be the cause of destruction, 

 than the spores or organs of fructification. For the 

 vegetative forms the action of destructive agents is 

 more or less rapid according to the case; a bacterium, 

 taken in full vegetation in a suitable medium, will be 

 more easily killed than one in the condition of latent 

 life, for example, in a state of desiccation, which is 

 equivalent to saying that death will be more easily 

 produced as life is more intense, more complete. 

 Something of the same kind is observed in higher 

 beings, the liability of these to suffer from adverse 

 conditions being greater as their requirements are 

 the more exacting. A young bacterium recently de- 

 veloped from a spore is more sensitive than an adult 

 bacterium which has attained its complete develop- 

 ment. 



1. Natural disinfecting agents. — These are light, des- 

 iccation, and oxygen. 



Light. — Light excites oxidation of the organic sub- 

 stances which enter into the constitution of germs, 

 and, as a consequence, involves the death of the lat- 

 ter. Other conditions being the same, solar light 

 acts more rapidly upon non-sporulated germs than 



