48 DAIRY BACTERIOLOGY 



examined a similar Plectridium form which was isolated from 

 cheese, but which differs from the last-mentioned organism in 

 being able to ferment calcium lactate and not thriving in the 

 absence of special sources of carbon. Further, it produces in milk 

 formic, butyric arid valerianic acids. Several poison -producing 

 pathogenic forms also belong to this group, e.g., Bacillus botulinus, 

 which forms poisons in sausages, and Bacillus tetani, the organism 

 of tetanus or lockjaw (Figs. 6 and 16c). 



The subject of putrefactive fermentation has been dealt with 

 at some length for two reasons : first, the putrefactive organisms 

 are the most harmful with which we have to deal in dairy practice, 

 and second, the ripening of cheese is a process of protein decom- 

 position which takes a special course thanks to the acid which is 

 always formed at the outset. 



The few milk bacteria which are not connected with the fermen- 

 tation processes already described will be dealt with in Part II. 



