STERILIZATION ANTISEPSIS FOOD PRESERVATION 79 



may perhaps be classed in the same category. These will be 

 considered in more detail in a later chapter. 



Antiseptics. Antiseptic and preservative agents prevent or 

 delay the development of bacteria, without killing them. Very 

 much the same agents are applied to prevent the growth of mi- 

 crobes in living tissues and consequent poisoning of the body 

 (antisepsis) as in preventing microbic development in dead 

 organic matter (food preservation). 



Of the physical antiseptics, dessication and cold are perhaps 

 of greatest importance. These agencies find application to the 

 living body as well as in preservation of dead material. Sub- 

 stances which increase osmotic pressure, sodium chloride and 

 sugar, are also employed to prevent microbic growth in foods. 



The chemical antiseptics are very numerous. In general 

 a germicide in higher dilution exhibits antiseptic effect. * Small 

 quantities of the inorganic acids, hydrochloric, nitric, sulphuric 

 or sulphurous acid, prevent bacterial growth. Even boric acid 

 which has little or no germicidal effect will delay or inhibit mi- 

 crobic development. Many organic acids possess inhibitive prop- 

 erties toward bacterial action. Acetic and lactic acids prob- 

 ably act merely by virtue of their acidity. Benzoic and salicylic 

 acids seem to be more antiseptic, probably by virtue of other 

 structural features in their molecules. Other organic substances, 

 such as phenol (carbolic acid) and formaldehyde in high dilu- 

 tions prevent or delay bacterial growth, and weaker germicides 

 such as alcohol, chloroform or ether, are fairly effective preserva- 

 tives. Oxidizing agents often decompose too rapidly to be of 

 much value as antiseptics. Iodine, however, is one member of 

 this group having considerable antiseptic value. 



Of the inorganic salts, mercuric chloride is most important. 

 Small quantities of this agent inhibit the multiplication of bac- 

 teria. It is extensively employed in antiseptic treatment of 

 wounds. The borates, nitrates and salicylates, the latter com- 

 pounds of an organic acid, also inhibit bacterial action to some 

 extent. 



