74 BACTERIOLOGY 



powder it has been extensively used in the disinfection of drinking 

 water and of swimming pools. Bromine and iodine have long 

 been employed in surgery, and solutions of iodine are often applied 

 to the skin before surgical incision. Iodine probably acts to 

 some extent as a germicide in this instance, but also as an anti- 

 septic, remaining in the skin for some time after its application. 

 Hydrogen peroxide is a germicide, as it quickly decomposes to 

 form water and oxygen. It is placed on the market in solutions 

 varying in strength from 10 to 30 volumes, the mode of expression 

 indicating that corresponding solutions will liberate ten to thirty 

 times their volume of oxygen when appropriately treated. It 

 decomposes rapidly when in contact with purulent secretions, 

 setting free abundant oxygen, and on this account is much used 

 for cleansing infected wounds. It deteriorates in strength so 

 rapidly that only fresh solutions of known strength should be 

 used. 



Potassium Permanganate. Koch asserts that a 3 per cent 

 solution will destroy anthrax spores in twenty-four hours, but 

 that a i per cent solution cannot be depended upon to kill patho- 

 genic organisms. Its disinfectant value in practice is very low 

 on account of its ready decomposition by inert material. In the 

 dilute solutions usually used for medicinal injections and irriga- 

 tions no disinfectant action occurs. 



lodoform. This substance possesses little if any disinfectant 

 power. It is mildly antiseptic in moist wounds, due to the gradual 

 liberation of small quantities of iodine. 



Inorganic Salts. Mercuric chloride, HgC^, is probably more 

 commonly used than any other one germicide. But Geppert, 

 whose work in this direction has been abundantly corroborated 

 by others, found that the potency of corrosive sublimate as a 

 germicide had been greatly overrated. The inhibitory action of 

 corrosive sublimate, on the other hand, is very great, and the 

 veriest trace of it left adhering to the bacteria is sufficient to 

 prevent them from growing. Corrosive sublimate is difficult 

 to remove by ordinary washing and traces of it remain even after 



