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gained their victory, there remains over and above a 

 sufficient quantity of them to confer safety against any 

 fresh parties of bacilli that may obtain an entrance. 

 It is obvious, therefore, that what his blood serum 

 can do for the host himself, it can do for others if 

 introduced into their systems. And whether we select 

 for our purpo.se an animal, whose species is known to 

 be not very susceptible to the disease for the time 

 being under treatment, and inoculate it with virus of 

 ordinary power, or on the other hand if by one of tlie 

 various means at our disposal we attenuate or weaken 

 some virus and use it on an animal which is susceptible, 

 it is equally obvious that in either case the subject 

 selected will have only a mild attack. That is to say, 

 his sanguineous antitoxins will gain an easy victory 

 over the toxins of the disease, and will afterwards 

 remain in pronounced excess in the serum of his blood. 

 If now the animal is bled to a moderate amount, and the 

 serum of the abstracted blood is first separated from the 

 corpuscles, and then filtered through porcelain to make 

 sure that no bacilli still remain in it, we have at once 

 the means of reinforcing the blood antitoxins of 

 another animal — for instance, a man — suffering in the 

 ordinary way from the same disease. This is effected 

 by injecting the curative and protective serum under 

 the skin in quantities proportionate not so much to 

 the size of the animal being treated, as to the severity 

 of his attack. It also logically follows, and is .so found 

 in practice, that if the serum be injected into a healthy, 

 but at the same time susceptible individual, he at once 

 acquires an imniunit}' against the disease for as long 

 as the added antitoxins remain unchanged, and can 

 witli perfect safety expose himself freely to the chances 

 of infection. 



The phenomenal success that has attended this 

 practical outcome of what has been called " rubbishing 

 science" in those diseases in which its adoption has 



