BACTERIAL VACCINES 261 



others as well. The following are some of the reasons for 

 this opinion : The above organisms are notoriously extremely 

 variable in their virulence. While there is no necessarily 

 close connection between virulence and antigenic property, 

 yet since virulence is so variable, it is rational to assume 

 that antigenic property is also extremely variable. Indi- 

 viduals vary just as much in susceptibility and hence in 

 reactive power, and generally speaking, an individual will 

 react better in the production of antibodies to a stimulus to 

 which he has been more or less subjected, i. e., to organisms 

 derived from his own body. 



In the preparation of a vaccine great care must be used 

 in heating so that the organisms are killed, but the antigens 

 are not destroyed. Many of the enzymes present in bac- 

 teria, especially the proteolytic ones, are not any more sen- 

 sitive to heat than are the antigens, hence are not destroyed 

 entirely. Therefore a vaccine kept in stock for long gradu- 

 ally has some of its antigens destroyed by the uninjured 

 enzymes present with them, and so loses in potency. There- 

 fore in treating a given infection it is well to make up a 

 vaccine from the lesion, use three or four doses and if more 

 are necessary make up a new vaccine. 



If the above statements are borne in mind and vaccines 

 are made and administered accordingly, the author is well 

 satisfied that much better results will be secured. 



In accordance, with the theory on which the use of vac- 

 cines is based, i. e., that they stimulate the body cells to 

 produce immunizing antibodies, it is clear that they are espe- 

 cially suitable in those infections in which the process is 

 localized and should not be of much value in general infec- 

 tions. In the latter case the cells of the body are stimulated 

 to produce antibodies by the circulating organisms, prob- 

 ably nearly to their limit, hence the introduction of more of 

 the same organisms, capable of stimulating though dead, is 

 apt to overtax the cells and do more harm than good. It is 

 not possible to tell accurately when this limit is reached, but 

 the clinical symptoms are a guide. If vaccines are used at 

 all in general infections they should be given in the early 

 stages and in small doses at first with close watch as to the 

 effect. Irt localized infections only the cells ,in the immedi- 



