96 THE CREAMERY PATRON'S HANDBOOK. 



if they are once introduced. The nutritive elements in it are either 

 in a soluble state or are readily converted into a condition that permits of 

 their absorption by the lower forms of plant life. The degree of concentra- 

 tion is also favorable to most forms. Condensed milk keeps because 

 the soluble solids are so concentrated that living germs cannot well 

 develop in it; in ordinary milk the more dilute condition permits de- 

 velopment. 



The chemical composition of milk is also favorable to germ activity. 

 In reaction it is nearly neutral, or if acid, the acidity is not usually suffi- 

 cient to inhibit the development of life that is otherwise capable of growth 

 in such a fluid. Not all of the milk constituents are of equal value as food 

 for micro-oganisms. The fat is not readily affected, hence butter is less 

 susceptible to biogenic defects than cheese. Both the sugar and the nitro- 

 genous elements are readily decomposed by a large number of micro-or- 

 ganisms. 



The lower forms of plant life such as the bacteria, yeasts and moulds 

 are the common organisms which are capable of existing in milk that dele- 

 teriously affect it. The first group is by far the most important; indeed, 

 the great majority of abnormal milks that may be ascribed to germ origin 

 are due to this type of organic life. In some instances, yeasts and moulds 

 have some effect, but their influence is usually more potent in the manu- 

 factured product than in fresh milk. 



HEALTHY MILK STERILE IN UDDER. While milk is so constituted 

 chemically and physically as to make an excellent food for these lower forms 

 of vegetable life, it is free from all traces of germ life in the milk glands of a 

 healthy animal. In a diseased animal the case may be different, especially 

 if the trouble exists in connection with the udder. An animal may be 

 suffering from some physiological trouble such as indigestion, stomach 

 or intestinal derangement, and yet the milk might retain its sterile prop- 

 erties. Indeed, the disturbed condition of the animal due to the disease 

 might be so grave as to seriously alter the chemical or even the physical 

 condition of the milk, and still the milk remain germ free. It is a very 

 prevalent notion that the ingestion of living germs with the food is the 

 way in which the milk becomes infected, but such is not the case. The 

 healthy animal, or even vegetable tissue for that matter, is free from for- 

 eign forms of life. Normal blood is perfectly sterile. In the functional 

 activity of organs, the secretions as secreted are likewise free from micro- 

 organisms. 



HOW MILK BECOMES INFECTED WITH GERM LIFE. 



While the milk is sterile when elaborated in the udder, it in- 

 variably becomes contaminated with living germs during the process of 

 milking. This need cause but little wonder when we consider the con- 

 ditions under which the milk is drawn. All of the surroundings of the 



