Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER IV BACTERIA OF MILK Unless drawn under special conditions, which are not obtainable in dairy practice, milk always contains bacteria. Some of them come from the udder; others are derived from the cow's skin, the dust of the fodder and litter, the milk vessels and utensils, the person and clothing of the milker, etc., and enter the milk during the process of milking and in the subsequent handling of the milk. They are, under normal conditions, non-pathogenic organisms, and, since they are always present in milk, are called the common milk bacteria. Under certain conditions, which are discussed in another chapter, milk contains also pathogenic bacteria. COMMON MILK BACTERIA Some of the non-pathogenic bacteria do not bring about any perceptible change in milk. Many of them, however, produce marked alterations, and it is because of their presence that milk is so extremely perishable or unstable. In growing in milk, these organisms split up certain constituents, notably the lactose and casein, into various products, some of which are capable of exerting an injurious effect upon persons drinking the milk, particularly children and invalid adults. Certain of these changes, including the more harmful kinds, may be considerably advanced before they are indicated by any alteration in the appearance, odor, or taste of the milk. Therefore, while the common milk bacteria are in themselves harmless, and while their growth in milk to a limitedextent is not attended with any appreciable injurious effects, their presence in large numbers is not desirable because it may be accompanied by harmful results. There are numerous species of these organisms. For facility of study as well as for practical purposes, it is convenient to group them according to the changes which they bri...