50 AGRICULTURE OF MAINE. 



dairymen should know what is the cause of the changes in milk, 

 how they come about and how they may be controlled. 



Milk when first drawn from the cow is nearly sterile, or con- 

 tains practically nothing which causes fermentations or changes. 

 The change with which we are most familiar is souring, though 

 there are many others, some of which we are more or less 

 familiar with. These changes are caused by the introduction 

 into the milk after it is drawn, of various vegetable organisms 

 called germs, ferments or bacteria. These germs first attack 

 the milk sugar and convert it into acid ; later the albuminoids 

 are attacked and last of all, the fats. The change takes place 

 in a very short time after the milk is drawn unless something is 

 done to prevent it and rapidly continues until the milk becomes 

 unfit for food. Milk being a solution and containing suitable 

 food for the germs, makes a most admirable place for their 

 development so long as the temperature remains the same as 

 when drawn, or even when allowed to cool to summer heat. 



Germs are found in almost everything, in great numbers 

 except in the healthy living tissue of plants and animals, and are 

 so small that it requires a powerful microscope to see them ; they 

 are so light and numerous that they are floating about in the 

 atmosphere, especially on particles of dust, by which means they 

 may gain access to the milk. 



The cow stable is usually filled with them, coming especially 

 from the dusty hay and straw or cobwebs, hairs and particles 

 of manure, so that milk in a dusty or dirty stable has become 

 heavily contaminated before the milking process is through and 

 the longer it remains in the stable, the greater is the infection. 

 At the temperature of the freshly drawn milk they multiply very 

 rapidly, doubling in about twenty minutes, thus causing a rapid 

 change in the milk which is so noticeable in warm weather if 

 milk is not cooled. 



Most germs are harmless except as they cause changes in the 

 milk, which render it unfit for food, though there is a class 

 that are disease producing, such as typhoid, diphtheria, tuber- 

 culosis, etc., but this class must be conveyed from the disease 

 itself and are not floating about except the disease is present 

 nearby. 



Water used in washing milk utensils, is often a source of 

 infecting milk with disease germs. 



