CHAPTER VI 



FERMENTATION IN MILK 



General Introductor>' Notes. Kinds of Fermentation : — i. Lactic Acid Fer- 

 mentation ; 2. Butyric Acid Fermentation ; 3. Alcoholic Fermentation ; 4. 

 TheXoagulative Fermentations. 5. Diseases of Milk : (i) Blue Milk, (2) 

 Red Milk, (3) Yellow Milk, (4) Bitter Milk, (5) Soapy Milk, (6) Ropy Milk. 

 The Prevention of Milk Anomalies. 



Introductory Notes. — The story of the discovery of the vital prin- 

 ciple in fermentation is one of the most interesting and instruc- 

 tive in the whole range of chemistry and physiology. Our 

 knowledge of fermentation, even now by no means complete, has 

 been slowly built up by nearly 250 years of careful observation 

 and^experiment, and the record forms one of the most brilliant 

 chapters in research. For its beginnings we have to go back to 

 the middle of the seventeenth century, when Antony von 

 Leeuwenhoek of Delft was busily engaged in inventing the micro- 

 scope and in describing what he saw through his simple lenses. 

 He it was who first saw and described bacteria and yeast cells. 

 Yet it was not until more than 100 years later that these "animal- 

 cula," as they were termed, were deemed to be anything more 

 than accidentally present in any fluid or substance containing 

 them. Plenciz of Vienna was one of the first to conceive the 

 idea that decomposition could only take place in the presence of 

 some of these " animalcula." This was in the middle of the 

 eighteenth century. Another 100 years passed by before it was 

 established beyond dispute that these micro-organisms had an 

 intimate causal relation to the great processes of fermentation, 

 putrefaction, and disease. This body of facts was, as we have said, 

 the outcome of the labours of many men working in various spheres. 

 The great question of spontaneous generation, the physiology of 

 digestion, the study of decomposition and fermentation, and the in- 

 vestigation of disease, were being approached from various points of 



