224 APPLIED IMMUNOLOGY 



pear perfectly clear after a certain time owing to 

 digestion of the previously discernible microorganisms. 

 On the other hand, it often happens that the bac- 

 terin becomes clouded or a precipitate forms, due to 

 the chemical action of the contained phenol. Such 

 bacterins should be immediately discarded. As a rule, 

 bacterial suspensions in trikresol-saline solution will 

 keep for months. It is alleged that typhoid bacterin 

 becomes inert after three months. 



Autogenous versus Stock Bacterins, — By an autog- 

 enous or personal bacterin is meant one that is pre- 

 pared from the particular bacterium or strain of bac- 

 terium cultured from the infected patient. A stock 

 or laboratory bacterin is understood to mean a prep- 

 aration in which the bacterium has been isolated from 

 another patient, who has suffered from a similar in- 

 fection. In view of the diversity of the strains of 

 many bacteria, notably the streptococcus, colon ba- 

 cillus, etc., also of the fact that not a few diseases are 

 caused by different bacteria, namely, abscess, acne, 

 etc., it is natural that the preferable and most scientific 

 procedure is to employ an autogenous bacterin when- 

 ever possible. The authors have often successfully 

 treated cases with an autogenous preparation after 

 stock bacterins have resulted in failure. Not infre- 

 quently it becomes expedient to use a stock prepara- 

 tion, at least while the autogenous bacterin is being 



