BACTERIOLOGY OF MILK 



CHAPTER I 



SOME GENERAL CONDITIONS AFFECTING BACTERIA IN MILK 



General Properties and Composition of Milk : — The Carbohydrates of Milk ; 

 the Proteids or Albuminoids of Milk ; the Fats and Salts of Milk. Chemical 

 Composition of Milk Products. The Physiology' of Milk : — The Secretion 

 of Milk and Influences bearing upon it ; Variation in the Composition of 

 Milk— (i) The Race of Cow; (2) the Period of Lactation; (3) Kind of 

 Fodder ; (4) Seasonal Variations ; (5) Interval between Times of Milking. 

 Milk as a Medium for Bacteria : — The Sources of Bacteria in Milk ; 

 Elements of Contamination. The Pathology of Milk. 



Before entering upon the study of milk from a bacteriological 

 point of view it is necessary to consider briefly some of its physical 

 and physiological characters. The further our research has led us 

 the more convinced have we become of the influence, direct and 

 indirect, of the external and internal conditions of milk upon its 

 bacterial flora. The physiological and biological characters of milk 

 and the varied conditions of dairying, and not simply the species 

 of bacteria which happen to gain access to the milk, demand the 

 careful and systematic study of the bacteriologist. It may be that 

 in the future we shall find that much more is dependent upoii 

 these external conditions than upon particular species of bacteria. 

 It has been said that upwards of two hundred distinct species of 

 ordinary milk bacteria have been found and described. Without 

 reflecting in the least upon the excellent work which such results 

 prove, we would venture to suggest in the first place that many of 

 these so-called " milk bacteria " are in reality purely saprophytic — 

 existing naturally in soil and dust, in manure, in hay and straw, 

 and in the general environment of cattle — rather than specifically 

 related to milk ; and in the second that a more careful study of the 

 exact biological characters, conditions, and life history of known 

 species would prove more fruitful and of greater permanent service 



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