200 MANUAL OF BACTERIOLOGY. 



converted into the insoluble chloride, and Httle if any germicidal 

 action takes place. To this fact may be ascribed the varying 

 clinical results reported. 



Many semi-proprietary silver compounds are on the market, 

 introduced to replace the nitrate and its objectionable features. 

 The most important are argentamin, argohin, protargol and 

 argyrol, all organic silver combinations. They do not combine 

 with chlorides, are less irritating than the nitrate, and, not coagu- 

 lating albumin, they possess greater penetrating power. Clin- 

 ical reports and investigations have been so contradictory thus 

 far that their value cannot be readily estimated. 



Carbolic Acid. — One of the most important and most widely 

 used germicides. It is usually employed in strengths of from 

 I to 5 per cent. A 3 per cent, solution will sometimes kill the 

 spores of a,nthrax after two days' exposure (see Bacillus anthra- 

 cis, Part IV.). In the absence of spores the anthrax bacillus 

 is destroyed by a i per cent, solution in one hour. The less re- 

 sistant pus cocci are destroyed rapidly by a 2 per cent, solution. 

 Combination with an equal proportion of hydrochloric acid en- 

 hances the efficacy of carboUc acid to a marked extent. This 

 is due to the prevention of albuminous combinations, thus allow- 

 ing greater penetration of the germicide. 



Many other substances closely related to carboUc acid are 

 used and possess marked germicidal properties. Among them 

 may be mentioned creolin, cresol and lysol. They are all 

 slightly superior to carbolic acid in actual germicidal value. 



Aniline Dyes. — Many of these substances, notably pyoktanin 

 (methyl- violet), possess germicidal properties. A solution of 

 1-5000 will kill the anthrax bacillus in two hours. A much 

 stronger solution, 1-150, is required to kill the typhoid bacil- 

 lus in the same time. Malachite-green is said to possess even 

 greater germicidal value than pyoktanin. Methylene-blue also 

 possesses considerable germicidal power. 



Formalin is a 40 per cent, aqueous solution of formaldehyde. 



