VACCINES IN TREATMENT OF DISEASE 249 



clear that our clinical knowledge is not sufficient 

 to decide such a question. We can only speak 

 theoretically, and theoretically we must admit 

 the existence of many strains of a given type of 

 microorganism and also the possibility of in- 

 dividual differences in the microorganisms. 

 Upon this basis, autogenous vaccines would ap- 

 pear to be preferable to stock vaccines, since 

 autogenous cultures comply with the scientific 

 requirements of a vaccine. 



From a practical standpoint, however, stock 

 vaccines are more satisfactory to use for vari- 

 ous reasons: (1) It is frequently impossible to 

 prepare an autogenous vaccine for lack of prop- 

 er facilities. (2) It requires several days to 

 prepare an autogenous vaccine and this necessi- 

 tates loss of valuable time in the treatment. 

 (.3) Since it has been demonstrated that differ- 

 ent cultures of the same species of bacteria vary 

 widely in their immunologic properties, it is ob- 

 vious that a polyvalent stock vaccine will pro- 

 duce an immunity which will be efficient for a 

 very large majority of infections caused by that 

 specific type of microorganism. (4) An auto- 

 genous vaccine adds materially to the cost of an 

 otherwise inexpensive treatment. 



