84 BACTERIOLOGY. 



complished, althougli an agent may have been employed 

 that would, under other circumstances, have given en- 

 tirely satisfactory results. 



An antiseptic is a body which, by its presence, pre- 

 vents the growth of bacteria without of necessity killing 

 them. A body may be an antiseptic without possessing 

 disinfecting properties to any very high degree, but a 

 disinfectant is always an antiseptic as well. 



A germicide is a body possessing the property of 

 killing bacteria. 



MODE OF ACTION OF DISINFECTANTS. In the de- 

 struction of bacteria by means of chemical substances 

 there occurs, most probably, a definite chemical reac- 

 tion that is to say, the characteristics both of the 

 bacteria and the agent employed in their destruction 

 are lost in the production of an inert third body, the 

 result of their combination. It is impossible to state 

 with certainty, as yet, that this is in general the case ; but 

 the evidence that is rapidly accruing from studies upon 

 disinfectants and their mode of action points strongly 

 to the accuracy of this belief. This reaction, in which 

 the typical structures of both bodies concerned are lost, 

 takes place between the agent employed for disinfection 

 and the protoplasm of the bacteria. For example, in 

 the reaction that is seen to take place between the salts 

 of mercury and albuminous bodies there results a 

 third compound, which has neither all the character- 

 istics of mercury nor of albumin, but partakes of 

 some of the peculiarities of both ; it is a combina- 

 tion of albumin and mercury, commonly known by the 

 indefinite term "albuminate of mercury." Some such 

 reaction as this apparently occurs when the soluble salts 

 of mercury are brought in contact with bacteria. This 



