EFFECT OF CHEMICAL ENVIEONMENT 137 



An antiseptic is any substance which will inhibit the 

 growth of microorganisms. It is, of course, true that if 

 growth is prevented the cells will die off more or less 

 rapidly. A substance which causes comparatively rapid 

 death is termed a germicide. It will be apparent that the 

 difference between antiseptic and germicide is quantitative 

 and not qualitative. Both kill bacteria, antiseptics slowly, 

 germicides rapidly. 



The term disinfectant is for practical purposes synon- 

 ymous with germicide. It is usually used with reference to 

 disease-producing or pathogenic bacteria. 



A preservative is an antiseptic substance which is added 

 to foods to prevent the growth of harmful microorganisms. 

 The term fumigant is sometimes applied to a gaseous disin- 

 fectant. A deodorant is a substance which will mask or 

 destroy obnoxious odors ; it is not necessarily a fumigant or 

 a disinfectant. A substance which will kill bacteria is said 

 to exert a bactericidal action. 



For convenience in discussion, substances capable of 

 destroying bacteria may be divided into three groups : first 

 those which will kill bacteria free in nature ; second, those 

 which may be injected into or absorbed by the body of man 

 or animal and will destroy microorganisms growing there; 

 third, those substances capable of killing microorganisms 

 which are produced by animals and are present in the blood 

 serum. 



The germicidal agents commonly used in the destruction 

 of microorganisms may be grouped under the headings of 

 electrolytes, including the acids, alkalies, and salts; the 

 nonelectrolytes, including the alcohols, aldehydes, ances- 

 thetics, the phenol derivatives, the essential oils; and lastly 

 the oxidizing agents, including oxygen, ozone, chlorine, and 

 similar materials. 



Characteristics of an Ideal Disinfectant. Certain char- 

 acteristics should be possessed by an ideal disinfectant. To 



