GERMICIDAL SERA 221 



ago Feran used living cholera bacilli subcutaneously as a vaccine against 

 this disease. Wright introduced typhoid vaccination with heated cul- 

 tures and this has proved highly successful and is now widely used, 

 not only among soldiers but among civilians. Strong recommends 

 highly attenuated typhoid cultures. Besredka combines active and 

 passive immunity in vaccination against typhoid. The growth from 

 a forty-eight hour agar-culture is mixed with a small amount of 

 salt solution. To this is added a homologous immune serum and the 

 mixture allowed to stand for twelve hours. This results in agglutina- 

 tion. The bacteria are washed in salt solution, heated to 56 C. for one 

 hour and then injected. Vaccines thus prepared cause no inflamma- 

 tion. The bacteria are sensitized or combined with the amboceptor 

 in the immune serum and probably are more easily split up when 

 introduced into the body. Dead and avirulent plague bacilli have 

 been employed as a vaccine against this disease. The serum of men 

 and animals actively immunized shows a higher bacteriolytic titer than 

 normal serum, but we are not sure that the increased resistance is 

 due solely to this. It must be evident that this method of securing 

 increased resistance to a given infection is in principle the same as 

 that secured by a light attack of the disease. The body cells learn how 

 to combat the infection. They learn how to elaborate a specific enzyme 

 which will destroy the specific bacteria if they should subsequently find 

 their way into the body. For instance, the blood of a man contains no 

 specific enzyme capable of destroying the cholera bacillus. A small 

 amount of this organism is injected under his skin, and the cells of his 

 body under this new irritant learn how to elaborate a specific enzyme 

 which destroys the cholera bacillus. Later, if he drinks water contain- 

 ing this organism, it must be plain that he has a distinct advantage over 

 the unvaccinated man in resisting the infection. The world is indebted 

 to the Spanish physician, Feran, who first had the intelligence and 

 courage to employ this method in combating cholera. He was wiser 

 than his time and from his work has come vaccination against typhoid 

 and plague in man. 



PfeifTer and Mark have endeavored to ascertain in what part of 

 the body this specific immunizing enzyme is formed. For this purpose 

 they inoculated rabbits and killing one from time to time tested 

 extracts from the various organs. They found that the bacteriolytic 



