20 BACTERIA 



septics, such as metallic salts, formalin, carbolic acid, cresol, 

 mineral acids, and essential oils, are powerful germicides; some 

 even in high dilution. / 



- According to Koch, absolute alcohol, glycerine, distilled water, 

 and concentrated sodium chloride solution do not affect anthrax 

 spores, even after acting on them for months. Halogen elements 

 (iodine, bromine, chlorine) are the most powerful germicides, s^ 

 J Free acids and alkalies must be very strong to act as disinfectants. 

 Excessive amounts of sugar, salt, glycerine, and the pyroligneous 

 acids act as destroyers, or inhibitors to bacterial growth in food stuffs.^ 

 ^/^Metals act as lethal agents in the presence of light and water, by 

 forming metallic peroxides, which either destroy the vitality of bac- 

 teria or hinder their growth. Silver, zinc, cadmium, bismuth, and 

 copper, have this action. Consequently silver wire, or foil, are 

 used in surgery because of their anti-septic action. Metallic 

 fillings in teeth prevent the growth of bacteria that cause caries, 

 vx Certain cells in the bodies of animals (leucocytes) and some ele- 

 ments of the blood serum, being bactericidal, are a powerful means 

 tff internal defense against infection, if 



^ If the water of the cytoplasm of bacterial cells is dried out, the 

 vitality of the organism suffers. The length of time required for 

 drying varies, anthrax spores resisting the process for over ten years. 

 Ancient methods of preserving foods from putrefying, and which are 

 still in vogue, depend upon the employment of some of these agents, 

 which are prejudicial to bacterial life. Meats are salted, pickled, 

 dried, or smoked. Fruits are dried, pickled, or immersed in strong 

 saccharine solution, in order to preserve them from decay, in every 

 instance, the absence of moisture, the excess of salt, sugar, or 

 vinegar, or the pyroligneous acid from the smoking, prevents 

 bacterial growth, and consequently, decay of the food stuff. The 

 products of bacterial growths often inhibit, or destroy, the cells that 

 made them, as well as other bacteria. B. pyocyaneus and S. 

 cholera, have this property of secreting autolytic ferments.y 



