TESTS OF DISINFECTION 41 



tities considerably less than are required to completely 

 destroy vitality. 



An agent, therefore, which in a certain proportion 

 and in a given time acts as a " germicide," in a smaller 

 quantity may act as an antiseptic i. e., may prevent 

 putrefactive decomposition by restraining the devel- 

 opment of the bacteria of putrefaction. Antiseptics 

 also prevent or retard the development of pathogenic 

 bacteria. It follows from this that germicides are 

 also antiseptics ; but the reverse of this proposition is 

 not true as a general statement, for all antiseptics are 

 not germicides. Thus alcohol, common salt, sul- 

 phate of iron, and many other substances which are 

 extensively used as antiseptics, have scarcely any 

 germicide power, even in concentrated solutions, 

 and consequently would be entirely unreliable as 

 disinfectants. 



Practically, antiseptics may accomplish the same 

 result in the long run as we obtain in a short time 

 by the use of disinfectants. If, for example, we pre- 

 vent the development of the germs of cholera, or 

 of typhoid fever, in an infected privy vault, by the 

 continued use of antiseptics, these germs will in time 

 lose their ability to grow, when introduced into a 

 suitable culture medium. But in the meantime there 

 is always the possibility that some of them may 

 escape, with the fluid contents of the vault, into the 



