252 AIDS TO BACTERIOLOGY 



excess proportionate to the amount of organic matter 

 present. When, as in the case of water, organic matter is 

 practically absent, disinfection is assured by a very small 

 percentage. ' Chloride of lime ' (a mixture of calcium 

 hypochlorite, hydrate, and chloride), hypochlorite of soda 

 (chloros), and hermitine are the best known sources of 

 available chlorine. The last is prepared for distribution at 

 Poplar by the electrolysis of a solution of sodium chloride 

 and magnesium chloride. Sodium hydroxide is added to 

 fix free hypochlorous acid, and acts as a preservative. 

 Much dissension has arisen over the value of this disin- 

 fectant, some authorities regarding it as stable and 

 powerful even in the presence of sewage or other organic 

 matter, and others as unstable and, in the presence of 

 organic matter, untrustworthy. 



The use of chlorine as a gaseous disinfectant has pro- 

 duced bronchitis and laryngitis, with a fatal ending. 

 Iodine employed as a 2 per cent, solution in potassium 

 iodide solution, or, even better, as an alcoholic tincture, 

 is a disinfectant of the first order for the primary treat- 

 ment of wounds, and for the disinfection of skin previous 

 to operation. The tincture is recommended in the 

 War Office memorandum. Its use in the field has ex- 

 tended its popularity. It is true that it stains the skin, 

 and that serious inflammations have resulted from the 

 injudicious use of tincture of iodine as a local application, 

 but these are trivial details compared with its efficiency 

 (see also p. 248). Delorme, Medical Inspector-General 

 of the French Army, points out that dressings impregnated 

 with perchloride of mercury and carbolic acid while iodine 

 is being used are apt to cause a troublesome dermatitis, 

 which does not occur when a simple aseptic dressing is 

 resorted to. The iodine of iodoform is gradually liberated 

 in contact with the enzymes of pus, blood, etc. Its 

 success is largely due to this continual production of 

 fresh iodine. Iodoform by itself is inert. Antiformin 

 (p. 68) actually dissolves proteins, mucus, and most 

 bacteria, and for many purposes is an excellent disinfectant. 

 Christian mentions a 5 per cent, solution as suitable. 



Metals. Some metals, especially copper and its alloys, 

 gradually kill adherent bacteria. In a liquid containing 

 bacteria, a sterile zone develops round the metal. Twenty- 

 four hour contact with bright copper plates has been 



