284 PHAGOCYTOSIS—OPSONINS 



the particular strain of that organism which is responsible 

 for the lesion. Stock vaccines are made up from organisms 

 like the infective agent in a given case but derived from 

 some other person or animal or from laboratory cultures. 

 Commercial vaccines are "stock" vaccines and are usually 

 "polyvalent" or even "mixed." A "polyvalent" vaccine 

 contains several strains of the infective agent and a "mixed" 

 contains several different organisms. 



Stock vaccines have shown their value when used as pre- 

 ventive inoculations, notably so in typhoid fever in man, 

 anthrax and black-leg in cattle. The author is strongly 

 of the opinion, not only from the extended literature on the 

 subject, but also from his own experience in animals, and 

 especially in human cases, that stock vaccines are much 

 inferior and much more uncertain in their action when used 

 in the treatment of an infection than are autogenous vaccines. 

 This applies particularly to those instances in which pneu- 

 mococci, streptococci, staphylococci and colon bacilli are the 

 causative agents, but to 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. Individuals 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 a long time 

 gradually has some of its antigens destroyed by the unin- 

 jured enzymes present with them, and so loses in potency. 

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



