144 AGEICULTUEAL AND INDUSTRIAL BACTEEIOLOGY 



preserving vegetables are various mixtures of benzoates and 

 salicylates. Their use is unnecessary and objectionable. 

 The preservative action of the creosotes, the principal dis- 

 infective agency of smoke in the preservation of meat, is 

 closely related to that of phenol. 



Many of the members of the series of aniline dyes have 

 decided antiseptic and disinfecting powers. They show 

 decided differences, however, in their effect on different 

 kinds or species of bacteria. For example, it has been found 

 possible quite completely to inhibit the growth of most of 

 the Gram-positive organisms by the presence of gentian 

 violet, the Gram-negative forms growing well in its pres- 

 ence. The so-called Endo medium is a mixture of basic 

 fuchsin and sulphites. It quite completely inhibits the 

 growth of most organisms other than those belonging to the 

 colon typhoid group of bacteria, that is to the genus Bac- 

 terium. Malachite green and other dyes have been used in 

 differential media, inhibiting growth of some kinds of bac- 

 teria and not interfering with the development of others. 



Oxidizing Agents. — The most important of the oxidiz- 

 ing agents which have been used for sterilization are 

 oxygen in the nascent condition, chlorine, the hypochlorites, 

 and potassium permanganate. Ozone (O3) has frequently 

 been heralded as an excellent fumigant. Various types of 

 so-called "ozonizers" and "ozonaters" have been placed 

 upon the market. "While concentrated ozone undoubtedly 

 has some destructive effect upon microorganisms, its pres- 

 ence in the air in considerable quantities is probably 

 decidedly more injurious to human heings than it is to the 

 microorganisms which may be present. Satisfactory and 

 reliable methods of utilizing ozone have not been worked 

 out. 



Calcium hypochlorite and various other hypochlorites are 

 used extensively in the purification of water. In the pres- 

 ence of organic matter these break up, releasing free ehlor- 



