THE INSTRUCTION OF BACTERIA 73 



Lbs. Pressure Temperature 



9 114.3 



10 115.6 



11 116.8 



12 118 



13 119.1 



14 120.2 



15 121.3 



16 . . . 122.4 



Lbs. Pressure Temperature 



17 123.3 



18 124.3 



20 126.2 



22 128.1 



24 129.3 



26 :.... 131.5 



28 133.1 



30 . . 134.6 



CHEMICAL AGENTS INJURIOUS TO BACTERIA 



Since the time of Koch's l fundamental researches upon chemical 

 disinfectants, the known number of these substances has been enor- 

 mously increased, and now embraces chemical agents of the most varied 

 constitution. It is thus manifestly impossible to refer the injurious in- 

 fluence which these substances exert upon bacteria to any uniform law of 

 action. The efficiency of a disinfecting agent, furthermore, is not alone 

 dependent upon the nature and concentrations of the substance itself, but 

 depends complexly upon the nature of the solvent in which it is employed, 

 the temperature prevailing during its application, the numbers and bio- 

 logical characteristics of the bacteria in question, and the time of ex- 

 posure. All these factors, therefore, must be considered in testing the 

 efficiency of any given disinfectant. While it is true, furthermore, 

 that all substances which in a given concentration exert bactericidal or 

 disinfecting action upon a microorganism, will in greater dilution act 

 antiseptic ally or inhibitively, no definite rules of proportion exist be- 

 tween the two values, which in each case must be determined by experi- 

 ment. 



Disinfectants Used in Solution. The actual processes which take place 

 in the injury of bacteria by disinfectants are to a large extent unknown. 

 In the case of strong acids, or strongly oxidizing substances, there may 

 be destruction of the bacterial body as a whole by rapid oxidation. 

 Other substances may act by coagulation of the bacterial protoplasm; 

 others again by diffusion through the cell membrane are able to enter into 

 chemical combination with the protoplasm and exert a toxic action. 

 Again, in other cases, a 'difference in tonicity between cell protoplasm 

 and disinfectant may tend to withdrawal of water from the bacterial 

 cell and consequent injury of the microorganism. 



Among the inorganic disinfectants the most important are the metallic 



i Koch, Arb. a. d. kais. Gesundheitsamt, i, 1881. 



