ANTISEPTICS AND DISINFECTANTS. 15! 



bacteria and their spores, is a true disinfectant ; and 

 excessive cold, which only benumbs them, retard- 

 ing their development without killing them, is an 

 antiseptic. 



Spores have a greater power of resisting the action 

 of these various agents than the parent cells, and 

 many species of micro-organisms differ from each 

 other in their resisting power. An exact knowledge 

 of the subject can, therefore, only be based upon 

 investigations which will determine the effect of 

 these agents upon pure cultivations of the different 

 micro-organisms causally related to putrefaction 

 and disease. In the latter case, especially, this is 

 not possible in the present state of our knowledge. 

 In some cases of communicable disease there is 

 considerable doubt as to the etiological importance 

 of the organisms which have been described ; in 

 other cases no organisms have as yet been dis- 

 covered, or the organisms cannot be artificially 

 cultivated, or the disease is not reproduced by 

 inoculation, so that there is no means of testing 

 whether the agents have had any effect. One can, 

 therefore, only draw general conclusions by selecting 

 some well-known pathogenic and non-pathogenic 

 micro-organisms, and considering the influence of 

 chemicals, of hot air, and of steam upon them, as 

 representing the effect upon the various contagia 

 of disease and the causes of putrefaction. 



Such knowledge must necessarily prove of the 

 greatest importance, to the sanitarian, who is con- 



