CHAPTEK IV 



MILK FERMENTATIONS 



In the study of medical bacteriology the specific causal 

 organism of any disease is the important thing ; hence great 

 emphasis is laid on the study of the organism in question, 

 its isolation and its identification. In dairy bacteriology the 

 various types of fermentations are not produced by a single 

 species, but rather by a group of organisms capable of caus- 

 ing, in a general way, similar chemical changes. The organ- 

 isms connected with these changes may differ much among 

 themselves. The ordinary souring of milk may be produced 

 by a host of bacteria having not only dissimilar morpholog- 

 ical characteristics but cultural ones as well ; some of them 

 are micrococci, others small bacilli, and yet others large rod- 

 shaped forms. In dairy bacteriology the character of the fer- 

 mentation and the nature of by-products formed in milk 

 are the important things. Hence the more detailed study 

 of specific organisms is of somewhat less importance than 

 in medical bacteriology. 



It is, however, very desirable for the student to study 

 representative organisms of each group, even though the 

 specific forms are not identified, for work of this character 

 is needed to teach the beginner the necessity of noting easily 

 overlooked cultural differences that would not be observed 

 except by close comparative study. In the detailed study 

 of any organism certain points in regard to the morphology, 

 cultural characteristics, and biochemical reactions must be 



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