THE DEATH OF BACTERIA. 33 



germicides would be a more proper term to apply. The 

 action of such agents depends on the variety of bacterium 

 to be killed, on its state of nutrition, whether it is in a 

 vegetative or a spored condition, on the temperature at 

 which the agent acts, on the medium in which it acts, and 

 on the nature of the chemical agent itself. Among inorganic 

 bodies the salts of the metals with high atomic weights act 

 more potently than those with lower, and the most powerful 

 antiseptic bodies are probably the perchloride and periodide 

 of mercury. The reaction of the agent is a point of great 

 importance ; as a general rule, the more powerful an acid is, 

 the greater is its capacity as a germicide. The importance 

 of oxidising and reducing agents as germicides has probably 

 been overestimated. Among organic bodies the members 

 of the aromatic series are all more or less potent the 

 favourite member for practical use being carbolic acid. In 

 comparing the action of antiseptic agents the all-important 

 point is their relative molecular constitution. From the 

 number of conditions we have enumerated, which must 

 be considered in estimating antisepticity, it is evidently 

 impossible to make definite statements as to the value of 

 particular agents unless all the conditions are stated. As a 

 general rule, however, the two solutions most commonly 

 used, which will kill the greatest variety of bacteria in the 

 shortest time, are a i in 20 solution of carbolic acid and a 

 i in 1000 solution of perchloride of mercury. 



