262 ESSENTIALS OF BACTERIOLOGY 



minor contagious diseases, instead of teaching the people a 

 lesson, create a false impression of security, and permit them 

 to* neglect the commoner means of ordinary cleanliness 

 because of this assumed virtue of fumigation. The whole 

 subject of fumigation and quarantine regulation needs more 

 careful investigation and study. 



A germicide is an agent capable of destroying bacterial life. 



An antiseptic solution or substance is one that can inhibit 

 or prevent the growth of bacteria without necessarily de- 

 stroying them. 



A disinfectant must be germicidal. 



A deodorant may have no germicidal or antiseptic properties. 



Preservatives are substances which prevent fermentation, 

 but they are not always germicides. 



In considering the value of a germicide, the strength in 

 which it acts is the main consideration. Some very weak 

 chemicals will inhibit and destroy the growth of bacteria if 

 used in sufficiently concentrated solutions. Some bacteria 

 will die in an acid medium; others are destroyed by too much 

 alkali. Some bacteria are very readily destroyed in pure 

 cultures, but are resistant to a considerable degree in the 

 body tissues. Again, a germicide may be ideal in laboratory 

 experiments, but wholly impractical at the clinic. 



A i : 300,000 solution of mercuric chlorid (corrosive sub- 

 limate) will prevent the development of anthrax spores, but 

 a i : 1000 solution is needed to destroy them. 



Germicides are tested by action in various dilutions or in 

 gaseous form on threads impregnated with virulent and spore- 

 forming organisms. The length of time is noted that it takes 

 to destroy anthrax bacilli or pyogenic organisms. 



The infected material is subjected to the solution and then 

 inoculated on media and compared with control, or tested for 

 virulence on animals. Spore-forming organisms are very 

 resistant to the most potent agents. 



Heat is perhaps the best general germicide. For all articles 

 that can be subjected to boiling or the direct flame there is 

 no safer agent. 



