INFECTION AND DISINFECTION. 777 



spores of the micro-organisms discovered in cases of splenic fever 

 have been found to be absolutely unaffected after lying for upward 

 of three months in a five-per-cent solution of carbolic acid in oil. It 

 has been also found that vaccine matter mixed with carbolic acid in 

 solution still retains its efficacy, and the question may therefore well 

 be asked whether the highly diluted carbolic vapor used for purposes 

 of aerial disinfection is not powerless to deal with an atmosphere 

 saturated with the germs of infectious diseases. 



When compelled to make use of water of a suspicious class, filtra- 

 tion and boiling constitute the most reliable methods of purification. 

 Spongy iron is upon the whole the most efficacious filtering material. 

 The water, especially if passed through sand afterward, comes out 

 quite clear and pure, and may be kept for a long time without showing 

 any signs of the production of living organisms. Charcoal filters, on 

 the other hand, certainly sometimes allow spores or germs to pass 

 through unchanged, and, when they are employed, boiling should 

 always be superadded. It is not sufficient to bring the water once to 

 the boiling-point ; in order to be efficacious, repeated boilings are 

 necessary, for the reasons given in a preceding paragraph. Milk of 

 a suspicious character should always be thus thoroughly boiled. Trav- 

 elers on the Continent do well to provide themselves with small 

 portable filters, now easily procurable, for in many places the drinking- 

 water is highly charged with impurities. It is satisfactory to know 

 than the tannin contained in tea is a purifying agent of some value as 

 regards organic matter present in water. 



It would take up too much space and would be foreign to the 

 purpose I had in view to describe all the methods of using the various 

 disinfectants which are now offered to the public. With regard to 

 many of them it is sufficient to say that their power has been absurdly 

 overestimated. It can not be too strongly insisted upon that deodori- 

 zation is by no means equivalent to disinfection. My object has been 

 to indicate in the first place what in the present state of our knowledge 

 seems to be the true theory as to the causation of infectious diseases, 

 and to show how obstacles are presented to more rapid scientific prog- 

 ress by the extreme minuteness of the organisms with which we have 

 to deal. With regard to disinfection, I have striven to prove how 

 entirely it must depend for its success on the specific action exercised 

 upon the disease-germs by the means employed. The realization of 

 this necessary relation can not fail to dispel many a fond belief with 

 regard to disinfectants ; but it will leave us with a more intelligent 

 and useful appreciation of their true properties, and, by revealing how 

 far we still are from the goal of complete knowledge, may even stimu- 

 late the investigator to explore paths of science which are yet unknown. 

 Virgil says, " Felix qui potuit renim cognoscere causas," and to noth- 

 ing is this aphorism nowadays more applicable than to a knowledge of 

 those agencies which produce infectious diseases. — Fortnightly Revieic. 



