212 GERMICIDES AND ANTISEPTICS. 



present an opalescent or milky appearance, from 

 the abundant development which has taken place 

 as the result of inoculation. 



When a pathogenic organism is used to test 

 the germicide power of chemical substances, we 

 may inoculate living animals instead of sterilized 

 culture-fluids. In this case, failure to produce the 

 characteristic symptoms of the disease is, of course, 

 to be taken as evidence that the vitality of the 

 pathogenic germs was destroyed before inocula- 

 tion. The most available organisms for such ex- 

 periments, in the present state of science, are the 

 bacillus of anthrax, the micrococcus of fowl-chol- 

 era, the bacterium of symptomatic anthrax, and 

 the micrococcus of induced septicaemia in the 

 rabbit. 



In a series of experiments made by the writer 

 in 1881, the last-named organism, as found in the 

 blood of a rabbit recently dead, served as the test. 

 The results were on the whole quite satisfactory 

 and definite ; but there are certain sources of error 

 connected with this method which should be borne 

 in mind. First. The test-organistn may be modi- 

 fied as regards reproductive activity without being 

 killed ; and, in this case, a modified form of dis- 

 ease may result from the inoculation, of so mild 

 a character as to escape observation. Second. An 

 animal which has suffered this modified form of 

 disease, enjoys protection, more or less perfect, 

 from future attacks, and if used for a subsequent 

 experiment may, by its immunity from the effects 



