92 Comparative Power of some Disinfectants. 



tion, and other allied processes are in their essential nature 

 chemical changes brought about in organic matters by the 

 functional activity of minute vegetable organisms ; these 

 changes being of a destructive character, consisting in the 

 reduction of complex substances into simpler ones. Certain 

 phenomena which specially obtrude themselves on our 

 notice, such as the formation of disagreeably smelling 

 matters in putrefaction, and the copious evolution of gas in 

 ordinary alcoholic fermentation, are mere accidents. Among 

 the allied processes referred to must be ranked, I think, the 

 changes going on in the animal economy in the course of 

 certain acute diseases, which, from their apparent analogy 

 with the phenomena of fermentation, have been long named 

 zymotic. The investigations of some of the best patholo- 

 gists of our own day have supplied evidence of a positive 

 kind in favour of that theory; and with reference to a few 

 of the acute contagious diseases there is, I think, satisfactory 

 proof that they owe their origin to microscopic organisms 

 belonging to the lowest order of plants. The doctrine of 

 the parasitic nature of the ordinary epidemic diseases, 

 founded partly on the analogy already mentioned, and more 

 recently on the results of exact observation and experiment, 

 has received a further confirmation from the beneficial 

 results following the use of well-known disinfectants having 

 a parisiticidal action in the cure, and still more in the pre- 

 vention, of some diseases of the kind now under considera- 

 tion. To prove the action of disinfectants in preventing or 

 checking putrefaction in substances liable to it is easy; but 

 when we have to deal with the living animal the matter 

 becomes much more complicated, and hence perhaps the 

 want of demonstrative force in the evidence adduced in 

 favour of the action of disinfectants as preventive and 

 curative agents in disease. An important step has been 

 recently made by subjecting the virus or contagious matter 

 of some diseases, such as glanders and vaccinia, to the 

 action of disinfecting agents, and then testing its power of 

 communicating the disease by inoculation. Such investiga- 

 tions have been carried on by Dr. Dougall, of Glasgow, and in 

 a more thorough way by Dr. Baxter, whose experiments are 

 fully described in the Reports of the Medical Officer of the 

 Privy Council for the year 1875. It is there clearly shown 

 that the ordinary disinfectants — carbolic acid, sulphurous 

 acid, and chlorine — destroy the contagious property of the 



