76 BACTERIOLOGY 



most resistant spores are prevented from developing in a cul- 

 ture medium containing 1-40,000. In combination, as potas- 

 sio-mercuric iodide, it has been used in soaps (McClintock) 

 with very favorable results. The substance is not extensively 

 employed, and further investigation is necessary to determine 

 its true value. 



Silver Nitrate. This salt probably occupies the next posi- 

 tion to the bichloride of mercury in germicidal power. Behr- 

 ing claims it to be superior to bichloride of mercury in albumin- 

 ous fluids. The anthrax bacillus is killed by a solution of 

 1-20,000 after two hours' exposure. At least forty-eight hours' 

 exposure to a 1-10,000 solution is required to kill the spores of 

 anthrax. It is very irritating, and possesses strong affinities 

 for chlorides, forming with them insoluble chloride of silver, a 

 salt without germicidal value. For these reasons the use of 

 silver nitrate is limited. In the solutions usually employed for 

 douching the cavities of the body the available silver nitrate is 

 immediately converted into the insoluble chloride, and little if 

 any germicidal action takes place. To this fact may be ascribed 

 the varying clinical results reported. 



Many proprietary silver compounds are on the market, in- 

 troduced to replace the nitrate and its objectionable features. 

 The most important are protargol and argyrol, organic silver 

 combinations. They do not combine with chlorides, are less 

 irritating than the nitrate and, not coagulating albumin, they 

 possess greater penetrating power. 



Organic Poisons. Carbolic acid is one of the most important 

 and most widely used disinfectants. It is usually employed in 

 strengths of from i to 5 per cent. A 3 per cent solution will 

 sometimes kill the spores of anthrax after two days' exposure. 

 In the absence of spores, the anthrax bacillus is destroyed by a i per 

 cent solution in one hour. The less resistant pus cocci are de- 

 stroyed rapidly by a 2 per cent solution. Combination with an 

 equal proportion of hydrochloric acid enhances the efficacy of 

 carbolic acid to a marked extent. This_is due to the prevention 



