ATTENUATION OF VIRUS. 207 



of the pathogenic organism. Evidently the tis- 

 sues of a susceptible animal are able to resist the 

 invasion of a limited number of active germs (di- 

 lution of virus), and of a still greater number of 

 those which are less active as a result of the 

 treatment referred to. 



The writer has obtained evidence, in the course 

 of his experiments relating to the comparative 

 value of disinfectants, which goes to show that 

 certain chemical reagents, also, may modify the 

 virulence of pathogenic bacteria in a similar man- 

 ner. In these experiments, the blood of a rabbit 

 recently dead from induced septicaemia was the 

 virulent fluid used as a test. The pathogenic or- 

 ganism in this case is a micrococcus, which is 

 found in normal human saliva. In the published 

 report of these experiments the following state- 

 ment is made : 



" The most important source of error, however, and 

 one which must be kept in view in future experiments, 

 is the fact that a protective influence has been shown to 

 result from the injection of virus, the virulence of which 

 has been modified, without being entirely destroyed, by 

 the agent used as a disinfectant." l 



Sodium hyposulphite and alcohol were the chem- 

 ical reagents which produced the result noted in 

 these experiments ; but it seems probable that a 

 variety of antiseptic substances will be found to 

 be equally effective, when used in the proper pro- 



1 Studies from the Biological Laboratory, Johns Hopkins University, 

 Vol. II. No. 2, p. 205. 



